Merge pull request #518 from simPod/fix-internal-directives

Fix internal directives

.gitattributes

@@ -2,6 +2,7 @@
 * text eol=lf
 /benchmarks export-ignore
 /tests export-ignore
+/examples export-ignore
 /tools export-ignore
 .gitattributes export-ignore
 .gitignore export-ignore

.gitignore

@@ -4,3 +4,4 @@ composer.phar
 phpcs.xml
 phpstan.neon
 vendor/
+/.idea

.scrutinizer.yml

@@ -20,7 +20,7 @@ build:
 
 tools:
     external_code_coverage:
-        timeout: 600
+        timeout: 900
 
 build_failure_conditions:
     - 'elements.rating(<= C).new.exists'                        # No new classes/methods with a rating of C or worse allowed

.travis.yml

@@ -4,12 +4,16 @@ language: php
 php:
   - 7.1
   - 7.2
+  - 7.3
+  - 7.4snapshot
   - nightly
 
 env:
   matrix:
-  - EXECUTOR=coroutine
+  - EXECUTOR= DEPENDENCIES=--prefer-lowest
+  - EXECUTOR=coroutine DEPENDENCIES=--prefer-lowest
   - EXECUTOR=
+  - EXECUTOR=coroutine
 
 
 cache:
@@ -26,13 +30,13 @@ script: ./vendor/bin/phpunit --group default,ReactPromise
 
 jobs:
   allow_failures:
+    - php: 7.4snapshot
     - php: nightly
 
   include:
     - stage: Test
-      env: DEPENDENCIES=low
       install:
-        - travis_retry composer update --prefer-dist --prefer-lowest
+        - travis_retry composer update --prefer-dist {$DEPENDENCIES}
 
     - stage: Test
       env: COVERAGE
@@ -40,10 +44,12 @@ jobs:
         - mv ~/.phpenv/versions/$(phpenv version-name)/etc/conf.d/xdebug.ini{.disabled,}
         - if [[ ! $(php -m | grep -si xdebug) ]]; then echo "xdebug required for coverage"; exit 1; fi
       script:
-        - ./vendor/bin/phpunit --coverage-clover clover.xml
+        - ./vendor/bin/phpunit --coverage-php /tmp/coverage/clover_executor.cov
+        - EXECUTOR=coroutine ./vendor/bin/phpunit --coverage-php /tmp/coverage/clover_executor-coroutine.cov
       after_script:
-        - wget https://scrutinizer-ci.com/ocular.phar
+        - ./vendor/bin/phpcov merge /tmp/coverage --clover /tmp/clover.xml
-        - php ocular.phar code-coverage:upload --format=php-clover clover.xml
+        - wget https://github.com/scrutinizer-ci/ocular/releases/download/1.5.2/ocular.phar
+        - php ocular.phar code-coverage:upload --format=php-clover /tmp/clover.xml
 
     - stage: Code Quality
       php: 7.1
@@ -57,3 +63,4 @@ jobs:
       env: STATIC_ANALYSIS
       install: travis_retry composer install --prefer-dist
       script: composer static-analysis
+

CHANGELOG.md

@@ -1,4 +1,26 @@
 # Changelog
+
+## Unreleased
+- Add schema validation: Input Objects must not contain non-nullable circular references (#492)
+
+#### v0.13.5
+- Fix coroutine executor when using with promise (#486) 
+
+#### v0.13.4
+- Force int when setting max query depth (#477)
+
+#### v0.13.3
+- Reverted minor possible breaking change (#476)
+
+#### v0.13.2
+- Added QueryPlan support (#436)
+- Fixed an issue with NodeList iteration over missing keys (#475)
+
+#### v0.13.1
+- Better validation of field/directive arguments
+- Support for apollo client/server persisted queries
+- Minor tweaks and fixes
+
 ## v0.13.0
 This release brings several breaking changes. Please refer to [UPGRADE](UPGRADE.md) document for details.
 

CONTRIBUTING.md

@@ -1,7 +1,6 @@
 # Contributing to GraphQL PHP
 
 ## Workflow
-
 If your contribution requires significant or breaking changes, or if you plan to propose a major new feature,
 we recommend you to create an issue on the [GitHub](https://github.com/webonyx/graphql-php/issues) with
 a brief proposal and discuss it with us first.
@@ -11,12 +10,14 @@ For smaller contributions just use this workflow:
 * Fork the project.
 * Add your features and or bug fixes.
 * Add tests. Tests are important for us.
-* Check your changes using `composer check-all`
+* Check your changes using `composer check-all`.
-* Send a pull request
+* Add an entry to the [Changelog's Unreleases section](CHANGELOG.md#unreleased).
+* Send a pull request.
+
+## Setup the Development Environment
+First, copy the URL of your fork and `git clone` it to your local machine.
 
-## Using GraphQL PHP from a Git checkout
 ```sh
-git clone https://github.com/webonyx/graphql-php.git
 cd graphql-php
 composer install
 ```
@@ -29,28 +30,26 @@ composer install
 Some tests have annotation `@see it('<description>')`. It is used for reference to same tests in [graphql-js implementation](https://github.com/graphql/graphql-js) with the same description.
 
 ## Coding Standard
-Coding standard of this project is based on [Doctrine CS](https://github.com/doctrine/coding-standard). To run the inspection:
+The coding standard of this project is based on [Doctrine CS](https://github.com/doctrine/coding-standard).
 
+Run the inspections:
 ```sh
 ./vendor/bin/phpcs
 ```
 
-Auto-fixing:
+Apply automatic code style fixes:
 ```sh
 ./vendor/bin/phpcbf
 ```
 
 ## Static analysis
-Based on [PHPStan](https://github.com/phpstan/phpstan)
+Based on [PHPStan](https://github.com/phpstan/phpstan).
 ```sh
 ./vendor/bin/phpstan analyse --ansi --memory-limit 256M
 ```
 
-
 ## Running benchmarks
-
+Benchmarks are run via [PHPBench](https://github.com/phpbench/phpbench).
-Benchmarks are run via phpbench:
-
 ```sh
 ./vendor/bin/phpbench run .
 ```

README.md

@@ -14,7 +14,7 @@ composer require webonyx/graphql-php
 ```
 
 ## Documentation
-Full documentation is available on the [Documentation site](http://webonyx.github.io/graphql-php/) as well 
+Full documentation is available on the [Documentation site](https://webonyx.github.io/graphql-php/) as well 
 as in the [docs](docs/) folder of the distribution.
 
 If you don't know what GraphQL is, visit this [official website](http://graphql.org) 
@@ -24,11 +24,29 @@ by the Facebook engineering team.
 There are several ready examples in the [examples](examples/) folder of the distribution with specific 
 README file per example.
 
-## Contribute
+## Contributors
-Please refer to [CONTRIBUTING.md](CONTRIBUTING.md) for information on how to contribute.
 
-## Old README.md
+This project exists thanks to [all the people](https://github.com/webonyx/graphql-php/graphs/contributors) who contribute. [[Contribute](CONTRIBUTING.md)].
-Here is a [link to the old README.md](https://github.com/webonyx/graphql-php/blob/v0.9.14/README.md). 
 
-Keep in mind that it relates to the version 0.9.x. It may contain outdated information for 
+## Backers
-newer versions (even though we try to preserve backwards compatibility).
+
+<a href="https://opencollective.com/webonyx-graphql-php#backers" target="_blank"><img src="https://opencollective.com/webonyx-graphql-php/backers.svg?width=890"></a>
+
+## Sponsors
+
+Support this project by becoming a sponsor. Your logo will show up here with a link to your website. [[Become a sponsor](https://opencollective.com/webonyx-graphql-php#sponsor)]
+
+<a href="https://opencollective.com/webonyx-graphql-php/sponsor/0/website" target="_blank"><img src="https://opencollective.com/webonyx-graphql-php/sponsor/0/avatar.svg"></a>
+<a href="https://opencollective.com/webonyx-graphql-php/sponsor/1/website" target="_blank"><img src="https://opencollective.com/webonyx-graphql-php/sponsor/1/avatar.svg"></a>
+<a href="https://opencollective.com/webonyx-graphql-php/sponsor/2/website" target="_blank"><img src="https://opencollective.com/webonyx-graphql-php/sponsor/2/avatar.svg"></a>
+<a href="https://opencollective.com/webonyx-graphql-php/sponsor/3/website" target="_blank"><img src="https://opencollective.com/webonyx-graphql-php/sponsor/3/avatar.svg"></a>
+<a href="https://opencollective.com/webonyx-graphql-php/sponsor/4/website" target="_blank"><img src="https://opencollective.com/webonyx-graphql-php/sponsor/4/avatar.svg"></a>
+<a href="https://opencollective.com/webonyx-graphql-php/sponsor/5/website" target="_blank"><img src="https://opencollective.com/webonyx-graphql-php/sponsor/5/avatar.svg"></a>
+<a href="https://opencollective.com/webonyx-graphql-php/sponsor/6/website" target="_blank"><img src="https://opencollective.com/webonyx-graphql-php/sponsor/6/avatar.svg"></a>
+<a href="https://opencollective.com/webonyx-graphql-php/sponsor/7/website" target="_blank"><img src="https://opencollective.com/webonyx-graphql-php/sponsor/7/avatar.svg"></a>
+<a href="https://opencollective.com/webonyx-graphql-php/sponsor/8/website" target="_blank"><img src="https://opencollective.com/webonyx-graphql-php/sponsor/8/avatar.svg"></a>
+<a href="https://opencollective.com/webonyx-graphql-php/sponsor/9/website" target="_blank"><img src="https://opencollective.com/webonyx-graphql-php/sponsor/9/avatar.svg"></a>
+
+## License
+
+See [LICENSE](LICENSE).

UPGRADE.md

@@ -1,3 +1,8 @@
+## Master
+
+### Breaking (major): dropped deprecations
+ - dropped deprecated `GraphQL\Schema`. Use `GraphQL\Type\Schema`.
+
 ## Upgrade v0.12.x > v0.13.x
 
 ### Breaking (major): minimum supported version of PHP
@@ -78,6 +83,9 @@ Parser::parse($source, [ 'allowLegacySDLImplementsInterfaces' => true])
 - `AbstractQuerySecurity` renamed to `QuerySecurityRule` (NS `GraphQL\Validator\Rules`)
 - `FindBreakingChanges` renamed to `BreakingChangesFinder` (NS `GraphQL\Utils`)
 
+### Breaking: new constructors
+
+`GraphQL\Type\Definition\ResolveInfo` now takes 10 arguments instead of one array.
 
 ## Upgrade v0.11.x > v0.12.x
 

benchmarks/Utils/SchemaGenerator.php

@@ -152,7 +152,7 @@ class SchemaGenerator
         ];
     }
 
-    public function resolveField($value, $args, $context, $resolveInfo)
+    public function resolveField($objectValue, $args, $context, $resolveInfo)
     {
         return $resolveInfo->fieldName . '-value';
     }

composer.json

@@ -9,16 +9,17 @@
     "API"
   ],
   "require": {
-    "php": "^7.1",
+    "php": "^7.1||^8.0",
     "ext-json": "*",
     "ext-mbstring": "*"
   },
   "require-dev": {
-    "doctrine/coding-standard": "^5.0",
+    "doctrine/coding-standard": "^6.0",
     "phpbench/phpbench": "^0.14.0",
-    "phpstan/phpstan": "0.10.5",
+    "phpstan/phpstan": "^0.11.12",
-    "phpstan/phpstan-phpunit": "0.10.0",
+    "phpstan/phpstan-phpunit": "^0.11.2",
-    "phpstan/phpstan-strict-rules": "0.10.1",
+    "phpstan/phpstan-strict-rules": "^0.11.1",
+    "phpunit/phpcov": "^5.0",
     "phpunit/phpunit": "^7.2",
     "psr/http-message": "^1.0",
     "react/promise": "2.*"

docs/complementary-tools.md

@@ -1,22 +1,26 @@
 # Integrations
 
-* [Integration with Relay](https://github.com/ivome/graphql-relay-php)
+* [Standard Server](executing-queries.md/#using-server) – Out of the box integration with any PSR-7 compatible framework (like [Slim](http://slimframework.com) or [Zend Expressive](http://zendframework.github.io/zend-expressive/)).
-* [Integration with Laravel 5](https://github.com/Folkloreatelier/laravel-graphql) + [Relay Helpers for Laravel](https://github.com/nuwave/laravel-graphql-relay) + [Nuwave Lighthouse](https://github.com/nuwave/lighthouse)
+* [Relay Library for graphql-php](https://github.com/ivome/graphql-relay-php) – Helps construct Relay related schema definitions.
-* [Symfony Bundle](https://github.com/overblog/GraphQLBundle) by Overblog
+* [Lighthouse](https://github.com/nuwave/lighthouse) – Laravel based, uses Schema Definition Language
-* Out of the box integration with any PSR-7 compatible framework (like [Slim](http://slimframework.com) or [Zend Expressive](http://zendframework.github.io/zend-expressive/)) via [Standard Server](executing-queries.md/#using-server)
+* [Laravel GraphQL](https://github.com/rebing/graphql-laravel) - Laravel wrapper for Facebook's GraphQL
+* [OverblogGraphQLBundle](https://github.com/overblog/GraphQLBundle) – Bundle for Symfony
+* [WP-GraphQL](https://github.com/wp-graphql/wp-graphql) - GraphQL API for WordPress
 
 # GraphQL PHP Tools
 
-* Define types with Doctrine ORM annotations ([for PHP7.1](https://github.com/Ecodev/graphql-doctrine), for [earlier PHP versions](https://github.com/rahuljayaraman/doctrine-graphql))
+* [GraphQLite](https://graphqlite.thecodingmachine.io) – Define your complete schema with annotations
-* [DataLoader PHP](https://github.com/overblog/dataloader-php) - as a ready implementation for [deferred resolvers](data-fetching.md#solving-n1-problem)
+* [GraphQL Doctrine](https://github.com/Ecodev/graphql-doctrine) – Define types with Doctrine ORM annotations
-* [PSR 15 compliant middleware](https://github.com/phps-cans/psr7-middleware-graphql) for the Standard Server (experimental)
+* [DataLoaderPHP](https://github.com/overblog/dataloader-php) – as a ready implementation for [deferred resolvers](data-fetching.md#solving-n1-problem)
-* [GraphQL Uploads](https://github.com/Ecodev/graphql-upload) for the Standard Server
+* [GraphQL Uploads](https://github.com/Ecodev/graphql-upload) – A PSR-15 middleware to support file uploads in GraphQL.
-* [GraphQL Batch Processor](https://github.com/vasily-kartashov/graphql-batch-processing) - Simple library that provides a builder interface for defining collection, querying, filtering, and post-processing logic of batched data fetches. 
+* [GraphQL Batch Processor](https://github.com/vasily-kartashov/graphql-batch-processing) – Provides a builder interface for defining collection, querying, filtering, and post-processing logic of batched data fetches. 
+* [GraphQL Utils](https://github.com/simPod/GraphQL-Utils) – Objective schema definition builders (no need for arrays anymore) and `DateTime` scalar
+* [PSR 15 compliant middleware](https://github.com/phps-cans/psr7-middleware-graphql) for the Standard Server _(experimental)_
 
 # General GraphQL Tools
 
-* [GraphiQL](https://github.com/graphql/graphiql) - An in-browser IDE for exploring GraphQL
+* [GraphQL Playground](https://github.com/prismagraphql/graphql-playground) – GraphQL IDE for better development workflows (GraphQL Subscriptions, interactive docs & collaboration).
+* [GraphiQL](https://github.com/graphql/graphiql) – An in-browser IDE for exploring GraphQL
 * [ChromeiQL](https://chrome.google.com/webstore/detail/chromeiql/fkkiamalmpiidkljmicmjfbieiclmeij)
-  or [GraphiQL Feen](https://chrome.google.com/webstore/detail/graphiql-feen/mcbfdonlkfpbfdpimkjilhdneikhfklp) -
+  or [GraphiQL Feen](https://chrome.google.com/webstore/detail/graphiql-feen/mcbfdonlkfpbfdpimkjilhdneikhfklp) –
   GraphiQL as Google Chrome extension
-* [GraphQL Playground](https://github.com/prismagraphql/graphql-playground) - GraphQL IDE for better development workflows (GraphQL Subscriptions, interactive docs & collaboration).

docs/data-fetching.md

@@ -103,23 +103,25 @@ for a field you simply override this default resolver.
 **graphql-php** provides following default field resolver:
 ```php
 <?php
-function defaultFieldResolver($source, $args, $context, \GraphQL\Type\Definition\ResolveInfo $info)
+function defaultFieldResolver($objectValue, $args, $context, \GraphQL\Type\Definition\ResolveInfo $info)
-{
+    {
-    $fieldName = $info->fieldName;
+        $fieldName = $info->fieldName;
-    $property = null;
+        $property  = null;
 
-    if (is_array($source) || $source instanceof \ArrayAccess) {
+        if (is_array($objectValue) || $objectValue instanceof \ArrayAccess) {
-        if (isset($source[$fieldName])) {
+            if (isset($objectValue[$fieldName])) {
-            $property = $source[$fieldName];
+                $property = $objectValue[$fieldName];
-        }
+            }
-    } else if (is_object($source)) {
+        } elseif (is_object($objectValue)) {
-        if (isset($source->{$fieldName})) {
+            if (isset($objectValue->{$fieldName})) {
-            $property = $source->{$fieldName};
+                $property = $objectValue->{$fieldName};
+            }
         }
+
+        return $property instanceof Closure
+            ? $property($objectValue, $args, $context, $info)
+            : $property;
     }
-
-    return $property instanceof Closure ? $property($source, $args, $context, $info) : $property;
-}
 ```
 
 As you see it returns value by key (for arrays) or property (for objects). 
@@ -161,7 +163,6 @@ $userType = new ObjectType([
 Keep in mind that **field resolver** has precedence over **default field resolver per type** which in turn
  has precedence over **default field resolver**.
 
-
 # Solving N+1 Problem
 Since: 0.9.0
 

docs/executing-queries.md

@@ -136,13 +136,13 @@ So for example following batch will require single DB request (if user field is
 ```json
 [
   {
-    "query": "{user(id: 1)} { id }"
+    "query": "{user(id: 1) { id }}"
   },
   {
-    "query": "{user(id: 2)} { id }"
+    "query": "{user(id: 2) { id }}"
   },
   {
-    "query": "{user(id: 3)} { id }"
+    "query": "{user(id: 3) { id }}"
   }
 ]
 ```

docs/getting-started.md

@@ -54,8 +54,8 @@ $queryType = new ObjectType([
             'args' => [
                 'message' => Type::nonNull(Type::string()),
             ],
-            'resolve' => function ($root, $args) {
+            'resolve' => function ($rootValue, $args) {
-                return $root['prefix'] . $args['message'];
+                return $rootValue['prefix'] . $args['message'];
             }
         ],
     ],

docs/index.md

@@ -7,7 +7,7 @@
 # About GraphQL
 
 GraphQL is a modern way to build HTTP APIs consumed by the web and mobile clients.
-It is intended to be a replacement for REST and SOAP APIs (even for **existing applications**).
+It is intended to be an alternative to REST and SOAP APIs (even for **existing applications**).
 
 GraphQL itself is a [specification](https://github.com/facebook/graphql) designed by Facebook
 engineers. Various implementations of this specification were written 
@@ -44,8 +44,8 @@ existing PHP frameworks, add support for Relay, etc.
 ## Current Status
 The first version of this library (v0.1) was released on August 10th 2015.
 
-The current version (v0.10) supports all features described by GraphQL specification 
+The current version supports all features described by GraphQL specification 
-(including April 2016 add-ons) as well as some experimental features like 
+as well as some experimental features like 
 [Schema Language parser](type-system/type-language.md) and 
 [Schema printer](reference.md#graphqlutilsschemaprinter).
 

docs/reference.md

@@ -33,7 +33,7 @@ See [related documentation](executing-queries.md).
  * fieldResolver:
  *    A resolver function to use when one is not provided by the schema.
  *    If not provided, the default field resolver is used (which looks for a
- *    value on the source value with the field's name).
+ *    value on the object value with the field's name).
  * validationRules:
  *    A set of rules for query validation step. Default value is all available rules.
  *    Empty array would allow to skip query validation (may be convenient for persisted
@@ -299,7 +299,7 @@ static function getNullableType($type)
 ```
 # GraphQL\Type\Definition\ResolveInfo
 Structure containing information useful for field resolution process.
-Passed as 3rd argument to every field resolver. See [docs on field resolving (data fetching)](data-fetching.md).
+Passed as 4th argument to every field resolver. See [docs on field resolving (data fetching)](data-fetching.md).
 
 **Class Props:** 
 ```php

docs/type-system/enum-types.md

@@ -158,7 +158,7 @@ $heroType = new ObjectType([
             'args' => [
                 'episode' => Type::nonNull($enumType)
             ],
-            'resolve' => function($_value, $args) {
+            'resolve' => function($hero, $args) {
                 return $args['episode'] === 5 ? true : false; 
             }
         ]

docs/type-system/input-types.md

@@ -114,7 +114,7 @@ Option | Type | Notes
 name | `string` | **Required.** Name of the input field. When not set - inferred from **fields** array key
 type | `Type` | **Required.** Instance of one of [Input Types](input-types.md) (**Scalar**, **Enum**, **InputObjectType** + any combination of those with **nonNull** and **listOf** modifiers)
 description | `string` | Plain-text description of this input field for clients (e.g. used by [GraphiQL](https://github.com/graphql/graphiql) for auto-generated documentation)
-defaultValue | `scalar` | Default value of this input field
+defaultValue | `scalar` | Default value of this input field. Use the internal value if specifying a default for an **enum** type
 
 # Using Input Object Type
 In the example above we defined our InputObjectType. Now let's use it in one of field arguments:
@@ -131,7 +131,7 @@ $queryType = new ObjectType([
             'type' => Type::listOf($storyType),
             'args' => [
                 'filters' => [
-                    'type' => Type::nonNull($filters),
+                    'type' => $filters,
                     'defaultValue' => [
                         'popular' => true
                     ]

docs/type-system/object-types.md

@@ -80,7 +80,7 @@ Option | Type | Notes
 name | `string` | **Required.** Name of the field. When not set - inferred from **fields** array key (read about [shorthand field definition](#shorthand-field-definitions) below)
 type | `Type` | **Required.** An instance of internal or custom type. Note: type must be represented by a single instance within one schema (see also [Type Registry](index.md#type-registry))
 args | `array` | An array of possible type arguments. Each entry is expected to be an array with keys: **name**, **type**, **description**, **defaultValue**. See [Field Arguments](#field-arguments) section below.
-resolve | `callable` | **function($value, $args, $context, [ResolveInfo](../reference.md#graphqltypedefinitionresolveinfo) $info)**<br> Given the **$value** of this type, it is expected to return actual value of the current field. See section on [Data Fetching](../data-fetching.md) for details
+resolve | `callable` | **function($objectValue, $args, $context, [ResolveInfo](../reference.md#graphqltypedefinitionresolveinfo) $info)**<br> Given the **$objectValue** of this type, it is expected to return actual value of the current field. See section on [Data Fetching](../data-fetching.md) for details
 complexity | `callable` | **function($childrenComplexity, $args)**<br> Used to restrict query complexity. The feature is disabled by default, read about [Security](../security.md#query-complexity-analysis) to use it.
 description | `string` | Plain-text description of this field for clients (e.g. used by [GraphiQL](https://github.com/graphql/graphiql) for auto-generated documentation)
 deprecationReason | `string` | Text describing why this field is deprecated. When not empty - field will not be returned by introspection queries (unless forced)
@@ -94,7 +94,7 @@ Option | Type | Notes
 name | `string` | **Required.** Name of the argument. When not set - inferred from **args** array key
 type | `Type` | **Required.** Instance of one of [Input Types](input-types.md) (**scalar**, **enum**, **InputObjectType** + any combination of those with **nonNull** and **listOf** modifiers)
 description | `string` | Plain-text description of this argument for clients (e.g. used by [GraphiQL](https://github.com/graphql/graphiql) for auto-generated documentation)
-defaultValue | `scalar` | Default value for this argument
+defaultValue | `scalar` | Default value for this argument. Use the internal value if specifying a default for an **enum** type
 
 # Shorthand field definitions
 Fields can be also defined in **shorthand** notation (with only **name** and **type** options):

docs/type-system/schema.md

@@ -62,7 +62,7 @@ $mutationType = new ObjectType([
                 'episode' => $episodeEnum,
                 'review' => $reviewInputObject
             ],
-            'resolve' => function($val, $args) {
+            'resolve' => function($rootValue, $args) {
                 // TODOC
             }
         ]

docs/type-system/type-language.md

@@ -81,7 +81,7 @@ $cacheFilename = 'cached_schema.php';
 
 if (!file_exists($cacheFilename)) {
     $document = Parser::parse(file_get_contents('./schema.graphql'));
-    file_put_contents($cacheFilename, "<?php\nreturn " . var_export(AST::toArray($document), true));
+    file_put_contents($cacheFilename, "<?php\nreturn " . var_export(AST::toArray($document), true) . ";\n");
 } else {
     $document = AST::fromArray(require $cacheFilename); // fromArray() is a lazy operation as well
 }

examples/00-hello-world/graphql.php

@@ -19,8 +19,8 @@ try {
                 'args' => [
                     'message' => ['type' => Type::string()],
                 ],
-                'resolve' => function ($root, $args) {
+                'resolve' => function ($rootValue, $args) {
-                    return $root['prefix'] . $args['message'];
+                    return $rootValue['prefix'] . $args['message'];
                 }
             ],
         ],
@@ -35,7 +35,7 @@ try {
                     'x' => ['type' => Type::int()],
                     'y' => ['type' => Type::int()],
                 ],
-                'resolve' => function ($root, $args) {
+                'resolve' => function ($calc, $args) {
                     return $args['x'] + $args['y'];
                 },
             ],

examples/01-blog/Blog/Type/CommentType.php

@@ -35,12 +35,12 @@ class CommentType extends ObjectType
                     Types::htmlField('body')
                 ];
             },
-            'resolveField' => function($value, $args, $context, ResolveInfo $info) {
+            'resolveField' => function($comment, $args, $context, ResolveInfo $info) {
                 $method = 'resolve' . ucfirst($info->fieldName);
                 if (method_exists($this, $method)) {
-                    return $this->{$method}($value, $args, $context, $info);
+                    return $this->{$method}($comment, $args, $context, $info);
                 } else {
-                    return $value->{$info->fieldName};
+                    return $comment->{$info->fieldName};
                 }
             }
         ];

examples/01-blog/Blog/Type/QueryType.php

@@ -57,8 +57,8 @@ class QueryType extends ObjectType
                 ],
                 'hello' => Type::string()
             ],
-            'resolveField' => function($val, $args, $context, ResolveInfo $info) {
+            'resolveField' => function($rootValue, $args, $context, ResolveInfo $info) {
-                return $this->{$info->fieldName}($val, $args, $context, $info);
+                return $this->{$info->fieldName}($rootValue, $args, $context, $info);
             }
         ];
         parent::__construct($config);

examples/01-blog/Blog/Type/StoryType.php

@@ -75,12 +75,12 @@ class StoryType extends ObjectType
             'interfaces' => [
                 Types::node()
             ],
-            'resolveField' => function($value, $args, $context, ResolveInfo $info) {
+            'resolveField' => function($story, $args, $context, ResolveInfo $info) {
                 $method = 'resolve' . ucfirst($info->fieldName);
                 if (method_exists($this, $method)) {
-                    return $this->{$method}($value, $args, $context, $info);
+                    return $this->{$method}($story, $args, $context, $info);
                 } else {
-                    return $value->{$info->fieldName};
+                    return $story->{$info->fieldName};
                 }
             }
         ];

examples/01-blog/Blog/Type/UserType.php

@@ -44,12 +44,12 @@ class UserType extends ObjectType
             'interfaces' => [
                 Types::node()
             ],
-            'resolveField' => function($value, $args, $context, ResolveInfo $info) {
+            'resolveField' => function($user, $args, $context, ResolveInfo $info) {
                 $method = 'resolve' . ucfirst($info->fieldName);
                 if (method_exists($this, $method)) {
-                    return $this->{$method}($value, $args, $context, $info);
+                    return $this->{$method}($user, $args, $context, $info);
                 } else {
-                    return $value->{$info->fieldName};
+                    return $user->{$info->fieldName};
                 }
             }
         ];

examples/02-shorthand/rootvalue.php

@@ -1,12 +1,12 @@
 <?php
 
 interface Resolver {
-    public function resolve($root, $args, $context);
+    public function resolve($rootValue, $args, $context);
 }
 
 class Addition implements Resolver
 {
-    public function resolve($root, $args, $context)
+    public function resolve($rootValue, $args, $context)
     {
         return $args['x'] + $args['y'];
     }
@@ -14,22 +14,22 @@ class Addition implements Resolver
 
 class Echoer implements Resolver
 {
-    public function resolve($root, $args, $context)
+    public function resolve($rootValue, $args, $context)
     {
-        return $root['prefix'].$args['message'];
+        return $rootValue['prefix'].$args['message'];
     }
 }
 
 return [
-    'sum' => function($root, $args, $context) {
+    'sum' => function($rootValue, $args, $context) {
         $sum = new Addition();
 
-        return $sum->resolve($root, $args, $context);
+        return $sum->resolve($rootValue, $args, $context);
     },
-    'echo' => function($root, $args, $context) {
+    'echo' => function($rootValue, $args, $context) {
         $echo = new Echoer();
 
-        return $echo->resolve($root, $args, $context);
+        return $echo->resolve($rootValue, $args, $context);
     },
     'prefix' => 'You said: ',
 ];

examples/03-server/graphql.php

@@ -19,8 +19,8 @@ try {
                 'args' => [
                     'message' => ['type' => Type::string()],
                 ],
-                'resolve' => function ($root, $args) {
+                'resolve' => function ($rootValue, $args) {
-                    return $root['prefix'] . $args['message'];
+                    return $rootValue['prefix'] . $args['message'];
                 }
             ],
         ],
@@ -35,7 +35,7 @@ try {
                     'x' => ['type' => Type::int()],
                     'y' => ['type' => Type::int()],
                 ],
-                'resolve' => function ($root, $args) {
+                'resolve' => function ($calc, $args) {
                     return $args['x'] + $args['y'];
                 },
             ],

phpstan.neon.dist

@@ -8,6 +8,8 @@ parameters:
     ignoreErrors:
         - "~Construct empty\\(\\) is not allowed\\. Use more strict comparison~"
         - "~(Method|Property) .+::.+(\\(\\))? (has parameter \\$\\w+ with no|has no return|has no) typehint specified~"
+        - "~Variable property access on .+~"
+        - "~Variable method call on static\\(GraphQL\\\\Server\\\\ServerConfig\\)~" # TODO get rid of
 
 includes:
 	- vendor/phpstan/phpstan-phpunit/extension.neon

src/Deferred.php

@@ -11,7 +11,7 @@ use Throwable;
 
 class Deferred
 {
-    /** @var SplQueue */
+    /** @var SplQueue|null */
     private static $queue;
 
     /** @var callable */
@@ -20,21 +20,6 @@ class Deferred
     /** @var SyncPromise */
     public $promise;
 
-    public static function getQueue()
-    {
-        return self::$queue ?: self::$queue = new SplQueue();
-    }
-
-    public static function runQueue()
-    {
-        $q = self::$queue;
-        while ($q && ! $q->isEmpty()) {
-            /** @var self $dfd */
-            $dfd = $q->dequeue();
-            $dfd->run();
-        }
-    }
-
     public function __construct(callable $callback)
     {
         $this->callback = $callback;
@@ -42,6 +27,25 @@ class Deferred
         self::getQueue()->enqueue($this);
     }
 
+    public static function getQueue() : SplQueue
+    {
+        if (self::$queue === null) {
+            self::$queue = new SplQueue();
+        }
+
+        return self::$queue;
+    }
+
+    public static function runQueue() : void
+    {
+        $queue = self::getQueue();
+        while (! $queue->isEmpty()) {
+            /** @var self $dequeuedNodeValue */
+            $dequeuedNodeValue = $queue->dequeue();
+            $dequeuedNodeValue->run();
+        }
+    }
+
     public function then($onFulfilled = null, $onRejected = null)
     {
         return $this->promise->then($onFulfilled, $onRejected);

src/Error/Error.php

@@ -122,13 +122,13 @@ class Error extends Exception implements JsonSerializable, ClientAware
 
         if ($previous instanceof ClientAware) {
             $this->isClientSafe = $previous->isClientSafe();
-            $this->category     = $previous->getCategory() ?: static::CATEGORY_INTERNAL;
+            $this->category     = $previous->getCategory() ?: self::CATEGORY_INTERNAL;
         } elseif ($previous) {
             $this->isClientSafe = false;
-            $this->category     = static::CATEGORY_INTERNAL;
+            $this->category     = self::CATEGORY_INTERNAL;
         } else {
             $this->isClientSafe = true;
-            $this->category     = static::CATEGORY_GRAPHQL;
+            $this->category     = self::CATEGORY_GRAPHQL;
         }
     }
 
@@ -148,10 +148,10 @@ class Error extends Exception implements JsonSerializable, ClientAware
         if ($error instanceof self) {
             if ($error->path && $error->nodes) {
                 return $error;
-            } else {
-                $nodes = $nodes ?: $error->nodes;
-                $path  = $path ?: $error->path;
             }
+
+            $nodes = $nodes ?: $error->nodes;
+            $path  = $path ?: $error->path;
         }
 
         $source     = $positions = $originalError = null;

src/Error/FormattedError.php

@@ -231,7 +231,7 @@ class FormattedError
      *
      * @param mixed[]   $formattedError
      * @param Throwable $e
-     * @param bool      $debug
+     * @param bool|int  $debug
      *
      * @return mixed[]
      *
@@ -297,7 +297,7 @@ class FormattedError
      * Prepares final error formatter taking in account $debug flags.
      * If initial formatter is not set, FormattedError::createFromException is used
      *
-     * @param  bool $debug
+     * @param  bool|int $debug
      *
      * @return callable|callable
      */

src/Error/InvariantViolation.php

@@ -7,8 +7,6 @@ namespace GraphQL\Error;
 use LogicException;
 
 /**
- * Class InvariantVoilation
- *
  * Note:
  * This exception should not inherit base Error exception as it is raised when there is an error somewhere in
  * user-land code

src/Error/UserError.php

@@ -7,8 +7,6 @@ namespace GraphQL\Error;
 use RuntimeException;
 
 /**
- * Class UserError
- *
  * Error caused by actions of GraphQL clients. Can be safely displayed to a client...
  */
 class UserError extends RuntimeException implements ClientAware

src/Error/Warning.php

@@ -4,6 +4,8 @@ declare(strict_types=1);
 
 namespace GraphQL\Error;
 
+use GraphQL\Exception\InvalidArgument;
+use function is_int;
 use function trigger_error;
 use const E_USER_WARNING;
 
@@ -15,12 +17,12 @@ use const E_USER_WARNING;
  */
 final class Warning
 {
-    const WARNING_ASSIGN             = 2;
+    public const WARNING_ASSIGN             = 2;
-    const WARNING_CONFIG             = 4;
+    public const WARNING_CONFIG             = 4;
-    const WARNING_FULL_SCHEMA_SCAN   = 8;
+    public const WARNING_FULL_SCHEMA_SCAN   = 8;
-    const WARNING_CONFIG_DEPRECATION = 16;
+    public const WARNING_CONFIG_DEPRECATION = 16;
-    const WARNING_NOT_A_TYPE         = 32;
+    public const WARNING_NOT_A_TYPE         = 32;
-    const ALL                        = 63;
+    public const ALL                        = 63;
 
     /** @var int */
     private static $enableWarnings = self::ALL;
@@ -37,7 +39,7 @@ final class Warning
      *
      * @api
      */
-    public static function setWarningHandler(?callable $warningHandler = null)
+    public static function setWarningHandler(?callable $warningHandler = null) : void
     {
         self::$warningHandler = $warningHandler;
     }
@@ -54,16 +56,16 @@ final class Warning
      *
      * @api
      */
-    public static function suppress($suppress = true)
+    public static function suppress($suppress = true) : void
     {
         if ($suppress === true) {
             self::$enableWarnings = 0;
         } elseif ($suppress === false) {
             self::$enableWarnings = self::ALL;
-        } else {
+        } elseif (is_int($suppress)) {
-            $suppress = (int) $suppress;
-
             self::$enableWarnings &= ~$suppress;
+        } else {
+            throw InvalidArgument::fromExpectedTypeAndArgument('bool|int', $suppress);
         }
     }
 
@@ -79,22 +81,22 @@ final class Warning
      *
      * @api
      */
-    public static function enable($enable = true)
+    public static function enable($enable = true) : void
     {
         if ($enable === true) {
             self::$enableWarnings = self::ALL;
         } elseif ($enable === false) {
             self::$enableWarnings = 0;
-        } else {
+        } elseif (is_int($enable)) {
-            $enable = (int) $enable;
-
             self::$enableWarnings |= $enable;
+        } else {
+            throw InvalidArgument::fromExpectedTypeAndArgument('bool|int', $enable);
         }
     }
 
-    public static function warnOnce($errorMessage, $warningId, $messageLevel = null)
+    public static function warnOnce(string $errorMessage, int $warningId, ?int $messageLevel = null) : void
     {
-        if (self::$warningHandler) {
+        if (self::$warningHandler !== null) {
             $fn = self::$warningHandler;
             $fn($errorMessage, $warningId);
         } elseif ((self::$enableWarnings & $warningId) > 0 && ! isset(self::$warned[$warningId])) {
@@ -103,9 +105,9 @@ final class Warning
         }
     }
 
-    public static function warn($errorMessage, $warningId, $messageLevel = null)
+    public static function warn(string $errorMessage, int $warningId, ?int $messageLevel = null) : void
     {
-        if (self::$warningHandler) {
+        if (self::$warningHandler !== null) {
             $fn = self::$warningHandler;
             $fn($errorMessage, $warningId);
         } elseif ((self::$enableWarnings & $warningId) > 0) {

src/Exception/InvalidArgument.php

@@ -0,0 +1,20 @@
+<?php
+
+declare(strict_types=1);
+
+namespace GraphQL\Exception;
+
+use InvalidArgumentException;
+use function gettype;
+use function sprintf;
+
+final class InvalidArgument extends InvalidArgumentException
+{
+    /**
+     * @param mixed $argument
+     */
+    public static function fromExpectedTypeAndArgument(string $expectedType, $argument) : self
+    {
+        return new self(sprintf('Expected type "%s", got "%s"', $expectedType, gettype($argument)));
+    }
+}

src/Executor/ExecutionContext.php

@@ -14,7 +14,7 @@ use GraphQL\Type\Schema;
  * Data that must be available at all points during query execution.
  *
  * Namely, schema of the type system that is currently executing,
- * and the fragments defined in the query document
+ * and the fragments defined in the query document.
  *
  * @internal
  */
@@ -45,28 +45,28 @@ class ExecutionContext
     public $errors;
 
     /** @var PromiseAdapter */
-    public $promises;
+    public $promiseAdapter;
 
     public function __construct(
         $schema,
         $fragments,
-        $root,
+        $rootValue,
         $contextValue,
         $operation,
-        $variables,
+        $variableValues,
         $errors,
         $fieldResolver,
         $promiseAdapter
     ) {
         $this->schema         = $schema;
         $this->fragments      = $fragments;
-        $this->rootValue      = $root;
+        $this->rootValue      = $rootValue;
         $this->contextValue   = $contextValue;
         $this->operation      = $operation;
-        $this->variableValues = $variables;
+        $this->variableValues = $variableValues;
         $this->errors         = $errors ?: [];
         $this->fieldResolver  = $fieldResolver;
-        $this->promises       = $promiseAdapter;
+        $this->promiseAdapter = $promiseAdapter;
     }
 
     public function addError(Error $error)

src/Executor/ExecutionResult.php

@@ -154,7 +154,7 @@ class ExecutionResult implements JsonSerializable
         }
 
         if (! empty($this->extensions)) {
-            $result['extensions'] = (array) $this->extensions;
+            $result['extensions'] = $this->extensions;
         }
 
         return $result;

src/Executor/Executor.php

@@ -74,7 +74,7 @@ class Executor
      * execution are collected in `$result->errors`.
      *
      * @param mixed|null               $rootValue
-     * @param mixed[]|null             $contextValue
+     * @param mixed|null               $contextValue
      * @param mixed[]|ArrayAccess|null $variableValues
      * @param string|null              $operationName
      *
@@ -119,8 +119,8 @@ class Executor
      *
      * Useful for async PHP platforms.
      *
-     * @param mixed[]|null $rootValue
+     * @param mixed|null   $rootValue
-     * @param mixed[]|null $contextValue
+     * @param mixed|null   $contextValue
      * @param mixed[]|null $variableValues
      * @param string|null  $operationName
      *
@@ -157,31 +157,33 @@ class Executor
 
     /**
      * If a resolve function is not given, then a default resolve behavior is used
-     * which takes the property of the source object of the same name as the field
+     * which takes the property of the root value of the same name as the field
      * and returns it as the result, or if it's a function, returns the result
      * of calling that function while passing along args and context.
      *
-     * @param mixed        $source
+     * @param mixed      $objectValue
-     * @param mixed[]      $args
+     * @param mixed[]    $args
-     * @param mixed[]|null $context
+     * @param mixed|null $context
      *
      * @return mixed|null
      */
-    public static function defaultFieldResolver($source, $args, $context, ResolveInfo $info)
+    public static function defaultFieldResolver($objectValue, $args, $context, ResolveInfo $info)
     {
         $fieldName = $info->fieldName;
         $property  = null;
 
-        if (is_array($source) || $source instanceof ArrayAccess) {
+        if (is_array($objectValue) || $objectValue instanceof ArrayAccess) {
-            if (isset($source[$fieldName])) {
+            if (isset($objectValue[$fieldName])) {
-                $property = $source[$fieldName];
+                $property = $objectValue[$fieldName];
             }
-        } elseif (is_object($source)) {
+        } elseif (is_object($objectValue)) {
-            if (isset($source->{$fieldName})) {
+            if (isset($objectValue->{$fieldName})) {
-                $property = $source->{$fieldName};
+                $property = $objectValue->{$fieldName};
             }
         }
 
-        return $property instanceof Closure ? $property($source, $args, $context, $info) : $property;
+        return $property instanceof Closure
+            ? $property($objectValue, $args, $context, $info)
+            : $property;
     }
 }

src/Executor/Promise/Adapter/SyncPromise.php

@@ -13,8 +13,6 @@ use function is_object;
 use function method_exists;
 
 /**
- * Class SyncPromise
- *
  * Simplistic (yet full-featured) implementation of Promises A+ spec for regular PHP `sync` mode
  * (using queue to defer promises execution)
  */
@@ -40,16 +38,16 @@ class SyncPromise
      */
     private $waiting = [];
 
-    public static function runQueue()
+    public static function runQueue() : void
     {
         $q = self::$queue;
-        while ($q && ! $q->isEmpty()) {
+        while ($q !== null && ! $q->isEmpty()) {
             $task = $q->dequeue();
             $task();
         }
     }
 
-    public function resolve($value)
+    public function resolve($value) : self
     {
         switch ($this->state) {
             case self::PENDING:
@@ -85,7 +83,7 @@ class SyncPromise
         return $this;
     }
 
-    public function reject($reason)
+    public function reject($reason) : self
     {
         if (! $reason instanceof Exception && ! $reason instanceof Throwable) {
             throw new Exception('SyncPromise::reject() has to be called with an instance of \Throwable');
@@ -109,7 +107,7 @@ class SyncPromise
         return $this;
     }
 
-    private function enqueueWaitingPromises()
+    private function enqueueWaitingPromises() : void
     {
         Utils::invariant(
             $this->state !== self::PENDING,
@@ -118,7 +116,7 @@ class SyncPromise
 
         foreach ($this->waiting as $descriptor) {
             self::getQueue()->enqueue(function () use ($descriptor) {
-                /** @var $promise self */
+                /** @var self $promise */
                 [$promise, $onFulfilled, $onRejected] = $descriptor;
 
                 if ($this->state === self::FULFILLED) {
@@ -147,17 +145,17 @@ class SyncPromise
         $this->waiting = [];
     }
 
-    public static function getQueue()
+    public static function getQueue() : SplQueue
     {
         return self::$queue ?: self::$queue = new SplQueue();
     }
 
     public function then(?callable $onFulfilled = null, ?callable $onRejected = null)
     {
-        if ($this->state === self::REJECTED && ! $onRejected) {
+        if ($this->state === self::REJECTED && $onRejected === null) {
             return $this;
         }
-        if ($this->state === self::FULFILLED && ! $onFulfilled) {
+        if ($this->state === self::FULFILLED && $onFulfilled === null) {
             return $this;
         }
         $tmp             = new self();

src/Executor/Promise/Adapter/SyncPromiseAdapter.php

@@ -160,7 +160,9 @@ class SyncPromiseAdapter implements PromiseAdapter
 
         if ($syncPromise->state === SyncPromise::FULFILLED) {
             return $syncPromise->result;
-        } elseif ($syncPromise->state === SyncPromise::REJECTED) {
+        }
+
+        if ($syncPromise->state === SyncPromise::REJECTED) {
             throw $syncPromise->result;
         }
 

src/Executor/ReferenceExecutor.php

@@ -115,8 +115,8 @@ class ReferenceExecutor implements ExecutorImplementation
      * Constructs an ExecutionContext object from the arguments passed to
      * execute, which we will pass throughout the other execution methods.
      *
-     * @param mixed[]             $rootValue
+     * @param mixed               $rootValue
-     * @param mixed[]             $contextValue
+     * @param mixed               $contextValue
      * @param mixed[]|Traversable $rawVariableValues
      * @param string|null         $operationName
      *
@@ -134,30 +134,30 @@ class ReferenceExecutor implements ExecutorImplementation
     ) {
         $errors    = [];
         $fragments = [];
-        /** @var OperationDefinitionNode $operation */
+        /** @var OperationDefinitionNode|null $operation */
         $operation                    = null;
         $hasMultipleAssumedOperations = false;
         foreach ($documentNode->definitions as $definition) {
-            switch ($definition->kind) {
+            switch (true) {
-                case NodeKind::OPERATION_DEFINITION:
+                case $definition instanceof OperationDefinitionNode:
-                    if (! $operationName && $operation) {
+                    if ($operationName === null && $operation !== null) {
                         $hasMultipleAssumedOperations = true;
                     }
-                    if (! $operationName ||
+                    if ($operationName === null ||
                         (isset($definition->name) && $definition->name->value === $operationName)) {
                         $operation = $definition;
                     }
                     break;
-                case NodeKind::FRAGMENT_DEFINITION:
+                case $definition instanceof FragmentDefinitionNode:
                     $fragments[$definition->name->value] = $definition;
                     break;
             }
         }
-        if (! $operation) {
+        if ($operation === null) {
-            if ($operationName) {
+            if ($operationName === null) {
-                $errors[] = new Error(sprintf('Unknown operation named "%s".', $operationName));
-            } else {
                 $errors[] = new Error('Must provide an operation.');
+            } else {
+                $errors[] = new Error(sprintf('Unknown operation named "%s".', $operationName));
             }
         } elseif ($hasMultipleAssumedOperations) {
             $errors[] = new Error(
@@ -165,7 +165,7 @@ class ReferenceExecutor implements ExecutorImplementation
             );
         }
         $variableValues = null;
-        if ($operation) {
+        if ($operation !== null) {
             [$coercionErrors, $coercedVariableValues] = Values::getVariableValues(
                 $schema,
                 $operation->variableDefinitions ?: [],
@@ -182,6 +182,7 @@ class ReferenceExecutor implements ExecutorImplementation
         }
         Utils::invariant($operation, 'Has operation if no errors.');
         Utils::invariant($variableValues !== null, 'Has variables if no errors.');
+
         return new ExecutionContext(
             $schema,
             $fragments,
@@ -198,7 +199,7 @@ class ReferenceExecutor implements ExecutorImplementation
     public function doExecute() : Promise
     {
         // Return a Promise that will eventually resolve to the data described by
-        // The "Response" section of the GraphQL specification.
+        // the "Response" section of the GraphQL specification.
         //
         // If errors are encountered while executing a GraphQL field, only that
         // field and its descendants will be omitted, and sibling fields will still
@@ -206,11 +207,12 @@ class ReferenceExecutor implements ExecutorImplementation
         // resolved Promise.
         $data   = $this->executeOperation($this->exeContext->operation, $this->exeContext->rootValue);
         $result = $this->buildResponse($data);
+
         // Note: we deviate here from the reference implementation a bit by always returning promise
         // But for the "sync" case it is always fulfilled
         return $this->isPromise($result)
             ? $result
-            : $this->exeContext->promises->createFulfilled($result);
+            : $this->exeContext->promiseAdapter->createFulfilled($result);
     }
 
     /**
@@ -228,13 +230,14 @@ class ReferenceExecutor implements ExecutorImplementation
         if ($data !== null) {
             $data = (array) $data;
         }
+
         return new ExecutionResult($data, $this->exeContext->errors);
     }
 
     /**
      * Implements the "Evaluating operations" section of the spec.
      *
-     * @param  mixed[] $rootValue
+     * @param  mixed $rootValue
      *
      * @return Promise|stdClass|mixed[]
      */
@@ -249,21 +252,26 @@ class ReferenceExecutor implements ExecutorImplementation
         //
         // Similar to completeValueCatchingError.
         try {
-            $result = $operation->operation === 'mutation' ?
+            $result = $operation->operation === 'mutation'
-                $this->executeFieldsSerially($type, $rootValue, $path, $fields) :
+                ? $this->executeFieldsSerially($type, $rootValue, $path, $fields)
-                $this->executeFields($type, $rootValue, $path, $fields);
+                : $this->executeFields($type, $rootValue, $path, $fields);
             if ($this->isPromise($result)) {
                 return $result->then(
                     null,
                     function ($error) {
-                        $this->exeContext->addError($error);
+                        if ($error instanceof Error) {
-                        return $this->exeContext->promises->createFulfilled(null);
+                            $this->exeContext->addError($error);
+
+                            return $this->exeContext->promiseAdapter->createFulfilled(null);
+                        }
                     }
                 );
             }
+
             return $result;
         } catch (Error $error) {
             $this->exeContext->addError($error);
+
             return null;
         }
     }
@@ -280,30 +288,33 @@ class ReferenceExecutor implements ExecutorImplementation
         switch ($operation->operation) {
             case 'query':
                 $queryType = $schema->getQueryType();
-                if (! $queryType) {
+                if ($queryType === null) {
                     throw new Error(
                         'Schema does not define the required query root type.',
                         [$operation]
                     );
                 }
+
                 return $queryType;
             case 'mutation':
                 $mutationType = $schema->getMutationType();
-                if (! $mutationType) {
+                if ($mutationType === null) {
                     throw new Error(
                         'Schema is not configured for mutations.',
                         [$operation]
                     );
                 }
+
                 return $mutationType;
             case 'subscription':
                 $subscriptionType = $schema->getSubscriptionType();
-                if (! $subscriptionType) {
+                if ($subscriptionType === null) {
                     throw new Error(
                         'Schema is not configured for subscriptions.',
                         [$operation]
                     );
                 }
+
                 return $subscriptionType;
             default:
                 throw new Error(
@@ -334,8 +345,8 @@ class ReferenceExecutor implements ExecutorImplementation
     ) {
         $exeContext = $this->exeContext;
         foreach ($selectionSet->selections as $selection) {
-            switch ($selection->kind) {
+            switch (true) {
-                case NodeKind::FIELD:
+                case $selection instanceof FieldNode:
                     if (! $this->shouldIncludeNode($selection)) {
                         break;
                     }
@@ -345,7 +356,7 @@ class ReferenceExecutor implements ExecutorImplementation
                     }
                     $fields[$name][] = $selection;
                     break;
-                case NodeKind::INLINE_FRAGMENT:
+                case $selection instanceof InlineFragmentNode:
                     if (! $this->shouldIncludeNode($selection) ||
                         ! $this->doesFragmentConditionMatch($selection, $runtimeType)
                     ) {
@@ -358,7 +369,7 @@ class ReferenceExecutor implements ExecutorImplementation
                         $visitedFragmentNames
                     );
                     break;
-                case NodeKind::FRAGMENT_SPREAD:
+                case $selection instanceof FragmentSpreadNode:
                     $fragName = $selection->name->value;
                     if (! empty($visitedFragmentNames[$fragName]) || ! $this->shouldIncludeNode($selection)) {
                         break;
@@ -366,7 +377,7 @@ class ReferenceExecutor implements ExecutorImplementation
                     $visitedFragmentNames[$fragName] = true;
                     /** @var FragmentDefinitionNode|null $fragment */
                     $fragment = $exeContext->fragments[$fragName] ?? null;
-                    if (! $fragment || ! $this->doesFragmentConditionMatch($fragment, $runtimeType)) {
+                    if ($fragment === null || ! $this->doesFragmentConditionMatch($fragment, $runtimeType)) {
                         break;
                     }
                     $this->collectFields(
@@ -378,6 +389,7 @@ class ReferenceExecutor implements ExecutorImplementation
                     break;
             }
         }
+
         return $fields;
     }
 
@@ -386,10 +398,8 @@ class ReferenceExecutor implements ExecutorImplementation
      * directives, where @skip has higher precedence than @include.
      *
      * @param FragmentSpreadNode|FieldNode|InlineFragmentNode $node
-     *
-     * @return bool
      */
-    private function shouldIncludeNode($node)
+    private function shouldIncludeNode($node) : bool
     {
         $variableValues = $this->exeContext->variableValues;
         $skipDirective  = Directive::skipDirective();
@@ -407,20 +417,16 @@ class ReferenceExecutor implements ExecutorImplementation
             $node,
             $variableValues
         );
-        if (isset($include['if']) && $include['if'] === false) {
+
-            return false;
+        return ! isset($include['if']) || $include['if'] !== false;
-        }
-        return true;
     }
 
     /**
      * Implements the logic to compute the key of a given fields entry
-     *
-     * @return string
      */
-    private static function getFieldEntryKey(FieldNode $node)
+    private static function getFieldEntryKey(FieldNode $node) : string
     {
-        return $node->alias ? $node->alias->value : $node->name->value;
+        return $node->alias === null ? $node->name->value : $node->alias->value;
     }
 
     /**
@@ -445,6 +451,7 @@ class ReferenceExecutor implements ExecutorImplementation
         if ($conditionalType instanceof AbstractType) {
             return $this->exeContext->schema->isPossibleType($conditionalType, $type);
         }
+
         return false;
     }
 
@@ -452,32 +459,34 @@ class ReferenceExecutor implements ExecutorImplementation
      * Implements the "Evaluating selection sets" section of the spec
      * for "write" mode.
      *
-     * @param mixed[]     $sourceValue
+     * @param mixed       $rootValue
      * @param mixed[]     $path
      * @param ArrayObject $fields
      *
      * @return Promise|stdClass|mixed[]
      */
-    private function executeFieldsSerially(ObjectType $parentType, $sourceValue, $path, $fields)
+    private function executeFieldsSerially(ObjectType $parentType, $rootValue, $path, $fields)
     {
         $result = $this->promiseReduce(
             array_keys($fields->getArrayCopy()),
-            function ($results, $responseName) use ($path, $parentType, $sourceValue, $fields) {
+            function ($results, $responseName) use ($path, $parentType, $rootValue, $fields) {
                 $fieldNodes  = $fields[$responseName];
                 $fieldPath   = $path;
                 $fieldPath[] = $responseName;
-                $result      = $this->resolveField($parentType, $sourceValue, $fieldNodes, $fieldPath);
+                $result      = $this->resolveField($parentType, $rootValue, $fieldNodes, $fieldPath);
                 if ($result === self::$UNDEFINED) {
                     return $results;
                 }
                 $promise = $this->getPromise($result);
-                if ($promise) {
+                if ($promise !== null) {
                     return $promise->then(static function ($resolvedResult) use ($responseName, $results) {
                         $results[$responseName] = $resolvedResult;
+
                         return $results;
                     });
                 }
                 $results[$responseName] = $result;
+
                 return $results;
             },
             []
@@ -487,32 +496,38 @@ class ReferenceExecutor implements ExecutorImplementation
                 return self::fixResultsIfEmptyArray($resolvedResults);
             });
         }
+
         return self::fixResultsIfEmptyArray($result);
     }
 
     /**
-     * Resolves the field on the given source object. In particular, this
+     * Resolves the field on the given root value.
-     * figures out the value that the field returns by calling its resolve function,
-     * then calls completeValue to complete promises, serialize scalars, or execute
-     * the sub-selection-set for objects.
      *
-     * @param object|null $source
+     * In particular, this figures out the value that the field returns
+     * by calling its resolve function, then calls completeValue to complete promises,
+     * serialize scalars, or execute the sub-selection-set for objects.
+     *
+     * @param mixed       $rootValue
      * @param FieldNode[] $fieldNodes
      * @param mixed[]     $path
      *
      * @return mixed[]|Exception|mixed|null
      */
-    private function resolveField(ObjectType $parentType, $source, $fieldNodes, $path)
+    private function resolveField(ObjectType $parentType, $rootValue, $fieldNodes, $path)
     {
         $exeContext = $this->exeContext;
         $fieldNode  = $fieldNodes[0];
         $fieldName  = $fieldNode->name->value;
         $fieldDef   = $this->getFieldDef($exeContext->schema, $parentType, $fieldName);
-        if (! $fieldDef) {
+        if ($fieldDef === null) {
             return self::$UNDEFINED;
         }
         $returnType = $fieldDef->getType();
-        // The resolve function's optional third argument is a collection of
+        // The resolve function's optional 3rd argument is a context value that
+        // is provided to every resolve function within an execution. It is commonly
+        // used to represent an authenticated user, or request-specific caches.
+        $context = $exeContext->contextValue;
+        // The resolve function's optional 4th argument is a collection of
         // information about the current execution state.
         $info = new ResolveInfo(
             $fieldName,
@@ -533,17 +548,13 @@ class ReferenceExecutor implements ExecutorImplementation
         } else {
             $resolveFn = $this->exeContext->fieldResolver;
         }
-        // The resolve function's optional third argument is a context value that
-        // is provided to every resolve function within an execution. It is commonly
-        // used to represent an authenticated user, or request-specific caches.
-        $context = $exeContext->contextValue;
         // Get the resolve function, regardless of if its result is normal
         // or abrupt (error).
         $result = $this->resolveOrError(
             $fieldDef,
             $fieldNode,
             $resolveFn,
-            $source,
+            $rootValue,
             $context,
             $info
         );
@@ -554,23 +565,21 @@ class ReferenceExecutor implements ExecutorImplementation
             $path,
             $result
         );
+
         return $result;
     }
 
     /**
      * This method looks up the field on the given type definition.
+     *
      * It has special casing for the two introspection fields, __schema
      * and __typename. __typename is special because it can always be
      * queried as a field, even in situations where no other fields
      * are allowed, like on a Union. __schema could get automatically
      * added to the query type, but that would require mutating type
      * definitions, which would cause issues.
-     *
-     * @param string $fieldName
-     *
-     * @return FieldDefinition
      */
-    private function getFieldDef(Schema $schema, ObjectType $parentType, $fieldName)
+    private function getFieldDef(Schema $schema, ObjectType $parentType, string $fieldName) : ?FieldDefinition
     {
         static $schemaMetaFieldDef, $typeMetaFieldDef, $typeNameMetaFieldDef;
         $schemaMetaFieldDef   = $schemaMetaFieldDef ?: Introspection::schemaMetaFieldDef();
@@ -578,39 +587,45 @@ class ReferenceExecutor implements ExecutorImplementation
         $typeNameMetaFieldDef = $typeNameMetaFieldDef ?: Introspection::typeNameMetaFieldDef();
         if ($fieldName === $schemaMetaFieldDef->name && $schema->getQueryType() === $parentType) {
             return $schemaMetaFieldDef;
-        } elseif ($fieldName === $typeMetaFieldDef->name && $schema->getQueryType() === $parentType) {
+        }
+
+        if ($fieldName === $typeMetaFieldDef->name && $schema->getQueryType() === $parentType) {
             return $typeMetaFieldDef;
-        } elseif ($fieldName === $typeNameMetaFieldDef->name) {
+        }
+
+        if ($fieldName === $typeNameMetaFieldDef->name) {
             return $typeNameMetaFieldDef;
         }
         $tmp = $parentType->getFields();
+
         return $tmp[$fieldName] ?? null;
     }
 
     /**
-     * Isolates the "ReturnOrAbrupt" behavior to not de-opt the `resolveField`
+     * Isolates the "ReturnOrAbrupt" behavior to not de-opt the `resolveField` function.
-     * function. Returns the result of resolveFn or the abrupt-return Error object.
+     * Returns the result of resolveFn or the abrupt-return Error object.
      *
      * @param FieldDefinition $fieldDef
      * @param FieldNode       $fieldNode
      * @param callable        $resolveFn
-     * @param mixed           $source
+     * @param mixed           $rootValue
      * @param mixed           $context
      * @param ResolveInfo     $info
      *
      * @return Throwable|Promise|mixed
      */
-    private function resolveOrError($fieldDef, $fieldNode, $resolveFn, $source, $context, $info)
+    private function resolveOrError($fieldDef, $fieldNode, $resolveFn, $rootValue, $context, $info)
     {
         try {
-            // Build hash of arguments from the field.arguments AST, using the
+            // Build a map of arguments from the field.arguments AST, using the
             // variables scope to fulfill any variable references.
             $args = Values::getArgumentValues(
                 $fieldDef,
                 $fieldNode,
                 $this->exeContext->variableValues
             );
-            return $resolveFn($source, $args, $context, $info);
+
+            return $resolveFn($rootValue, $args, $context, $info);
         } catch (Exception $error) {
             return $error;
         } catch (Throwable $error) {
@@ -658,20 +673,23 @@ class ReferenceExecutor implements ExecutorImplementation
                 $result
             );
             $promise   = $this->getPromise($completed);
-            if ($promise) {
+            if ($promise !== null) {
                 return $promise->then(
                     null,
                     function ($error) use ($exeContext) {
                         $exeContext->addError($error);
-                        return $this->exeContext->promises->createFulfilled(null);
+
+                        return $this->exeContext->promiseAdapter->createFulfilled(null);
                     }
                 );
             }
+
             return $completed;
         } catch (Error $err) {
             // If `completeValueWithLocatedError` returned abruptly (threw an error), log the error
             // and return null.
             $exeContext->addError($err);
+
             return null;
         }
     }
@@ -704,11 +722,11 @@ class ReferenceExecutor implements ExecutorImplementation
                 $result
             );
             $promise   = $this->getPromise($completed);
-            if ($promise) {
+            if ($promise !== null) {
                 return $promise->then(
                     null,
                     function ($error) use ($fieldNodes, $path) {
-                        return $this->exeContext->promises->createRejected(Error::createLocatedError(
+                        return $this->exeContext->promiseAdapter->createRejected(Error::createLocatedError(
                             $error,
                             $fieldNodes,
                             $path
@@ -716,6 +734,7 @@ class ReferenceExecutor implements ExecutorImplementation
                     }
                 );
             }
+
             return $completed;
         } catch (Exception $error) {
             throw Error::createLocatedError($error, $fieldNodes, $path);
@@ -763,7 +782,7 @@ class ReferenceExecutor implements ExecutorImplementation
     ) {
         $promise = $this->getPromise($result);
         // If result is a Promise, apply-lift over completeValue.
-        if ($promise) {
+        if ($promise !== null) {
             return $promise->then(function (&$resolved) use ($returnType, $fieldNodes, $info, $path) {
                 return $this->completeValue($returnType, $fieldNodes, $info, $path, $resolved);
             });
@@ -786,6 +805,7 @@ class ReferenceExecutor implements ExecutorImplementation
                     'Cannot return null for non-nullable field ' . $info->parentType . '.' . $info->fieldName . '.'
                 );
             }
+
             return $completed;
         }
         // If result is null-like, return null.
@@ -800,7 +820,7 @@ class ReferenceExecutor implements ExecutorImplementation
         // instance than `resolveType` or $field->getType() or $arg->getType()
         if ($returnType !== $this->exeContext->schema->getType($returnType->name)) {
             $hint = '';
-            if ($this->exeContext->schema->getConfig()->typeLoader) {
+            if ($this->exeContext->schema->getConfig()->typeLoader !== null) {
                 $hint = sprintf(
                     'Make sure that type loader returns the same instance as defined in %s.%s',
                     $info->parentType,
@@ -838,7 +858,7 @@ class ReferenceExecutor implements ExecutorImplementation
      */
     private function isPromise($value)
     {
-        return $value instanceof Promise || $this->exeContext->promises->isThenable($value);
+        return $value instanceof Promise || $this->exeContext->promiseAdapter->isThenable($value);
     }
 
     /**
@@ -854,17 +874,19 @@ class ReferenceExecutor implements ExecutorImplementation
         if ($value === null || $value instanceof Promise) {
             return $value;
         }
-        if ($this->exeContext->promises->isThenable($value)) {
+        if ($this->exeContext->promiseAdapter->isThenable($value)) {
-            $promise = $this->exeContext->promises->convertThenable($value);
+            $promise = $this->exeContext->promiseAdapter->convertThenable($value);
             if (! $promise instanceof Promise) {
                 throw new InvariantViolation(sprintf(
                     '%s::convertThenable is expected to return instance of GraphQL\Executor\Promise\Promise, got: %s',
-                    get_class($this->exeContext->promises),
+                    get_class($this->exeContext->promiseAdapter),
                     Utils::printSafe($promise)
                 ));
             }
+
             return $promise;
         }
+
         return null;
     }
 
@@ -878,7 +900,7 @@ class ReferenceExecutor implements ExecutorImplementation
      * @param mixed[]            $values
      * @param Promise|mixed|null $initialValue
      *
-     * @return mixed[]
+     * @return mixed
      */
     private function promiseReduce(array $values, callable $callback, $initialValue)
     {
@@ -886,11 +908,12 @@ class ReferenceExecutor implements ExecutorImplementation
             $values,
             function ($previous, $value) use ($callback) {
                 $promise = $this->getPromise($previous);
-                if ($promise) {
+                if ($promise !== null) {
                     return $promise->then(static function ($resolved) use ($callback, $value) {
                         return $callback($resolved, $value);
                     });
                 }
+
                 return $callback($previous, $value);
             },
             $initialValue
@@ -898,37 +921,40 @@ class ReferenceExecutor implements ExecutorImplementation
     }
 
     /**
-     * Complete a list value by completing each item in the list with the
+     * Complete a list value by completing each item in the list with the inner type.
-     * inner type
      *
-     * @param FieldNode[] $fieldNodes
+     * @param FieldNode[]         $fieldNodes
-     * @param mixed[]     $path
+     * @param mixed[]             $path
-     * @param mixed       $result
+     * @param mixed[]|Traversable $results
      *
      * @return mixed[]|Promise
      *
      * @throws Exception
      */
-    private function completeListValue(ListOfType $returnType, $fieldNodes, ResolveInfo $info, $path, &$result)
+    private function completeListValue(ListOfType $returnType, $fieldNodes, ResolveInfo $info, $path, &$results)
     {
         $itemType = $returnType->getWrappedType();
         Utils::invariant(
-            is_array($result) || $result instanceof Traversable,
+            is_array($results) || $results instanceof Traversable,
             'User Error: expected iterable, but did not find one for field ' . $info->parentType . '.' . $info->fieldName . '.'
         );
         $containsPromise = false;
         $i               = 0;
         $completedItems  = [];
-        foreach ($result as $item) {
+        foreach ($results as $item) {
             $fieldPath     = $path;
             $fieldPath[]   = $i++;
+            $info->path    = $fieldPath;
             $completedItem = $this->completeValueCatchingError($itemType, $fieldNodes, $info, $fieldPath, $item);
-            if (! $containsPromise && $this->getPromise($completedItem)) {
+            if (! $containsPromise && $this->getPromise($completedItem) !== null) {
                 $containsPromise = true;
             }
             $completedItems[] = $completedItem;
         }
-        return $containsPromise ? $this->exeContext->promises->all($completedItems) : $completedItems;
+
+        return $containsPromise
+            ? $this->exeContext->promiseAdapter->all($completedItems)
+            : $completedItems;
     }
 
     /**
@@ -979,7 +1005,7 @@ class ReferenceExecutor implements ExecutorImplementation
             $runtimeType = self::defaultTypeResolver($result, $exeContext->contextValue, $info, $returnType);
         }
         $promise = $this->getPromise($runtimeType);
-        if ($promise) {
+        if ($promise !== null) {
             return $promise->then(function ($resolvedRuntimeType) use (
                 $returnType,
                 $fieldNodes,
@@ -1001,6 +1027,7 @@ class ReferenceExecutor implements ExecutorImplementation
                 );
             });
         }
+
         return $this->completeObjectValue(
             $this->ensureValidRuntimeType(
                 $runtimeType,
@@ -1040,7 +1067,8 @@ class ReferenceExecutor implements ExecutorImplementation
         ) {
             return $value['__typename'];
         }
-        if ($abstractType instanceof InterfaceType && $info->schema->getConfig()->typeLoader) {
+
+        if ($abstractType instanceof InterfaceType && $info->schema->getConfig()->typeLoader !== null) {
             Warning::warnOnce(
                 sprintf(
                     'GraphQL Interface Type `%s` returned `null` from its `resolveType` function ' .
@@ -1062,23 +1090,25 @@ class ReferenceExecutor implements ExecutorImplementation
                 continue;
             }
             $promise = $this->getPromise($isTypeOfResult);
-            if ($promise) {
+            if ($promise !== null) {
                 $promisedIsTypeOfResults[$index] = $promise;
             } elseif ($isTypeOfResult) {
                 return $type;
             }
         }
         if (! empty($promisedIsTypeOfResults)) {
-            return $this->exeContext->promises->all($promisedIsTypeOfResults)
+            return $this->exeContext->promiseAdapter->all($promisedIsTypeOfResults)
                 ->then(static function ($isTypeOfResults) use ($possibleTypes) {
                     foreach ($isTypeOfResults as $index => $result) {
                         if ($result) {
                             return $possibleTypes[$index];
                         }
                     }
+
                     return null;
                 });
         }
+
         return null;
     }
 
@@ -1101,7 +1131,7 @@ class ReferenceExecutor implements ExecutorImplementation
         $isTypeOf = $returnType->isTypeOf($result, $this->exeContext->contextValue, $info);
         if ($isTypeOf !== null) {
             $promise = $this->getPromise($isTypeOf);
-            if ($promise) {
+            if ($promise !== null) {
                 return $promise->then(function ($isTypeOfResult) use (
                     $returnType,
                     $fieldNodes,
@@ -1111,6 +1141,7 @@ class ReferenceExecutor implements ExecutorImplementation
                     if (! $isTypeOfResult) {
                         throw $this->invalidReturnTypeError($returnType, $result, $fieldNodes);
                     }
+
                     return $this->collectAndExecuteSubfields(
                         $returnType,
                         $fieldNodes,
@@ -1123,6 +1154,7 @@ class ReferenceExecutor implements ExecutorImplementation
                 throw $this->invalidReturnTypeError($returnType, $result, $fieldNodes);
             }
         }
+
         return $this->collectAndExecuteSubfields(
             $returnType,
             $fieldNodes,
@@ -1151,7 +1183,7 @@ class ReferenceExecutor implements ExecutorImplementation
     /**
      * @param FieldNode[] $fieldNodes
      * @param mixed[]     $path
-     * @param mixed[]     $result
+     * @param mixed       $result
      *
      * @return mixed[]|Promise|stdClass
      *
@@ -1164,6 +1196,7 @@ class ReferenceExecutor implements ExecutorImplementation
         &$result
     ) {
         $subFieldNodes = $this->collectSubFields($returnType, $fieldNodes);
+
         return $this->executeFields($returnType, $result, $path, $subFieldNodes);
     }
 
@@ -1189,6 +1222,7 @@ class ReferenceExecutor implements ExecutorImplementation
             }
             $this->subFieldCache[$returnType][$fieldNodes] = $subFieldNodes;
         }
+
         return $this->subFieldCache[$returnType][$fieldNodes];
     }
 
@@ -1196,24 +1230,24 @@ class ReferenceExecutor implements ExecutorImplementation
      * Implements the "Evaluating selection sets" section of the spec
      * for "read" mode.
      *
-     * @param mixed|null  $source
+     * @param mixed       $rootValue
      * @param mixed[]     $path
      * @param ArrayObject $fields
      *
      * @return Promise|stdClass|mixed[]
      */
-    private function executeFields(ObjectType $parentType, $source, $path, $fields)
+    private function executeFields(ObjectType $parentType, $rootValue, $path, $fields)
     {
         $containsPromise = false;
         $finalResults    = [];
         foreach ($fields as $responseName => $fieldNodes) {
             $fieldPath   = $path;
             $fieldPath[] = $responseName;
-            $result      = $this->resolveField($parentType, $source, $fieldNodes, $fieldPath);
+            $result      = $this->resolveField($parentType, $rootValue, $fieldNodes, $fieldPath);
             if ($result === self::$UNDEFINED) {
                 continue;
             }
-            if (! $containsPromise && $this->getPromise($result)) {
+            if (! $containsPromise && $this->getPromise($result) !== null) {
                 $containsPromise = true;
             }
             $finalResults[$responseName] = $result;
@@ -1222,6 +1256,7 @@ class ReferenceExecutor implements ExecutorImplementation
         if (! $containsPromise) {
             return self::fixResultsIfEmptyArray($finalResults);
         }
+
         // Otherwise, results is a map from field name to the result
         // of resolving that field, which is possibly a promise. Return
         // a promise that will return this same map, but with any
@@ -1241,6 +1276,7 @@ class ReferenceExecutor implements ExecutorImplementation
         if ($results === []) {
             return new stdClass();
         }
+
         return $results;
     }
 
@@ -1259,19 +1295,20 @@ class ReferenceExecutor implements ExecutorImplementation
     {
         $keys              = array_keys($assoc);
         $valuesAndPromises = array_values($assoc);
-        $promise           = $this->exeContext->promises->all($valuesAndPromises);
+        $promise           = $this->exeContext->promiseAdapter->all($valuesAndPromises);
+
         return $promise->then(static function ($values) use ($keys) {
             $resolvedResults = [];
             foreach ($values as $i => $value) {
                 $resolvedResults[$keys[$i]] = $value;
             }
+
             return self::fixResultsIfEmptyArray($resolvedResults);
         });
     }
 
     /**
      * @param string|ObjectType|null $runtimeTypeOrName
-     * @param FieldNode[]            $fieldNodes
      * @param mixed                  $result
      *
      * @return ObjectType
@@ -1282,9 +1319,9 @@ class ReferenceExecutor implements ExecutorImplementation
         ResolveInfo $info,
         &$result
     ) {
-        $runtimeType = is_string($runtimeTypeOrName) ?
+        $runtimeType = is_string($runtimeTypeOrName)
-            $this->exeContext->schema->getType($runtimeTypeOrName) :
+            ? $this->exeContext->schema->getType($runtimeTypeOrName)
-            $runtimeTypeOrName;
+            : $runtimeTypeOrName;
         if (! $runtimeType instanceof ObjectType) {
             throw new InvariantViolation(
                 sprintf(
@@ -1318,6 +1355,7 @@ class ReferenceExecutor implements ExecutorImplementation
                 )
             );
         }
+
         return $runtimeType;
     }
 }

src/Executor/Values.php

@@ -92,7 +92,7 @@ class Values
                             ),
                             [$varDefNode]
                         );
-                    } elseif ($varDefNode->defaultValue) {
+                    } elseif ($varDefNode->defaultValue !== null) {
                         $coercedValues[$varName] = AST::valueFromAST($varDefNode->defaultValue, $varType);
                     }
                 }
@@ -196,7 +196,7 @@ class Values
             $argType           = $argumentDefinition->getType();
             $argumentValueNode = $argumentValueMap[$name] ?? null;
 
-            if (! $argumentValueNode) {
+            if ($argumentValueNode === null) {
                 if ($argumentDefinition->defaultValueExists()) {
                     $coercedValues[$name] = $argumentDefinition->defaultValue;
                 } elseif ($argType instanceof NonNull) {
@@ -209,7 +209,7 @@ class Values
             } elseif ($argumentValueNode instanceof VariableNode) {
                 $variableName = $argumentValueNode->name->value;
 
-                if ($variableValues && array_key_exists($variableName, $variableValues)) {
+                if ($variableValues !== null && array_key_exists($variableName, $variableValues)) {
                     // Note: this does not check that this variable value is correct.
                     // This assumes that this query has been validated and the variable
                     // usage here is of the correct type.
@@ -273,6 +273,7 @@ class Values
                     return $error->getMessage();
                 },
                 $errors
-            ) : [];
+            )
+            : [];
     }
 }

src/Experimental/Executor/Collector.php

@@ -64,7 +64,7 @@ class Collector
         foreach ($documentNode->definitions as $definitionNode) {
             /** @var DefinitionNode|Node $definitionNode */
 
-            if ($definitionNode->kind === NodeKind::OPERATION_DEFINITION) {
+            if ($definitionNode instanceof OperationDefinitionNode) {
                 /** @var OperationDefinitionNode $definitionNode */
                 if ($operationName === null && $this->operation !== null) {
                     $hasMultipleAssumedOperations = true;
@@ -74,7 +74,7 @@ class Collector
                 ) {
                     $this->operation = $definitionNode;
                 }
-            } elseif ($definitionNode->kind === NodeKind::FRAGMENT_DEFINITION) {
+            } elseif ($definitionNode instanceof FragmentDefinitionNode) {
                 /** @var FragmentDefinitionNode $definitionNode */
                 $this->fragments[$definitionNode->name->value] = $definitionNode;
             }
@@ -86,11 +86,13 @@ class Collector
             } else {
                 $this->runtime->addError(new Error('Must provide an operation.'));
             }
+
             return;
         }
 
         if ($hasMultipleAssumedOperations) {
             $this->runtime->addError(new Error('Must provide operation name if query contains multiple operations.'));
+
             return;
         }
 
@@ -194,24 +196,26 @@ class Collector
                 }
             }
 
-            if ($selection->kind === NodeKind::FIELD) {
+            if ($selection instanceof FieldNode) {
                 /** @var FieldNode $selection */
 
-                $resultName = $selection->alias ? $selection->alias->value : $selection->name->value;
+                $resultName = $selection->alias === null ? $selection->name->value : $selection->alias->value;
 
                 if (! isset($this->fields[$resultName])) {
                     $this->fields[$resultName] = [];
                 }
 
                 $this->fields[$resultName][] = $selection;
-            } elseif ($selection->kind === NodeKind::FRAGMENT_SPREAD) {
+            } elseif ($selection instanceof FragmentSpreadNode) {
                 /** @var FragmentSpreadNode $selection */
 
                 $fragmentName = $selection->name->value;
 
                 if (isset($this->visitedFragments[$fragmentName])) {
                     continue;
-                } elseif (! isset($this->fragments[$fragmentName])) {
+                }
+
+                if (! isset($this->fragments[$fragmentName])) {
                     $this->runtime->addError(new Error(
                         sprintf('Fragment "%s" does not exist.', $fragmentName),
                         $selection
@@ -245,7 +249,7 @@ class Collector
                 }
 
                 $this->doCollectFields($runtimeType, $fragmentDefinition->selectionSet);
-            } elseif ($selection->kind === NodeKind::INLINE_FRAGMENT) {
+            } elseif ($selection instanceof InlineFragmentNode) {
                 /** @var InlineFragmentNode $selection */
 
                 if ($selection->typeCondition !== null) {

src/Experimental/Executor/CoroutineExecutor.php

@@ -147,14 +147,16 @@ class CoroutineExecutor implements Runtime, ExecutorImplementation
             if ($emptyObjectAsStdClass && empty($array)) {
                 return new stdClass();
             }
+
             return $array;
         }
 
         if (is_array($value)) {
             $array = [];
-            foreach ($value as $item) {
+            foreach ($value as $key => $item) {
-                $array[] = self::resultToArray($item);
+                $array[$key] = self::resultToArray($item);
             }
+
             return $array;
         }
 
@@ -291,13 +293,17 @@ class CoroutineExecutor implements Runtime, ExecutorImplementation
                         $strand->stack[$strand->depth++] = $strand->current;
                         $strand->current                 = $value;
                         goto START;
-                    } elseif ($this->promiseAdapter->isThenable($value)) {
+                    } elseif ($this->isPromise($value)) {
                         // !!! increment pending before calling ->then() as it may invoke the callback right away
                         ++$this->pending;
 
+                        if (! $value instanceof Promise) {
+                            $value = $this->promiseAdapter->convertThenable($value);
+                        }
+
                         $this->promiseAdapter
-                            ->convertThenable($value)
                             ->then(
+                                $value,
                                 function ($value) use ($strand) {
                                     $strand->success = true;
                                     $strand->value   = $value;
@@ -365,6 +371,7 @@ class CoroutineExecutor implements Runtime, ExecutorImplementation
         // short-circuit evaluation for __typename
         if ($ctx->shared->fieldName === Introspection::TYPE_NAME_FIELD_NAME) {
             $ctx->result->{$ctx->shared->resultName} = $ctx->type->name;
+
             return;
         }
 
@@ -475,7 +482,7 @@ class CoroutineExecutor implements Runtime, ExecutorImplementation
     private function completeValueFast(CoroutineContext $ctx, Type $type, $value, array $path, &$returnValue) : bool
     {
         // special handling of Throwable inherited from JS reference implementation, but makes no sense in this PHP
-        if ($this->promiseAdapter->isThenable($value) || $value instanceof Throwable) {
+        if ($this->isPromise($value) || $value instanceof Throwable) {
             return false;
         }
 
@@ -491,7 +498,7 @@ class CoroutineExecutor implements Runtime, ExecutorImplementation
 
         if ($type !== $this->schema->getType($type->name)) {
             $hint = '';
-            if ($this->schema->getConfig()->typeLoader) {
+            if ($this->schema->getConfig()->typeLoader !== null) {
                 $hint = sprintf(
                     'Make sure that type loader returns the same instance as defined in %s.%s',
                     $ctx->type,
@@ -571,7 +578,7 @@ class CoroutineExecutor implements Runtime, ExecutorImplementation
 
         // !!! $value might be promise, yield to resolve
         try {
-            if ($this->promiseAdapter->isThenable($value)) {
+            if ($this->isPromise($value)) {
                 $value = yield $value;
             }
         } catch (Throwable $reason) {
@@ -613,8 +620,9 @@ class CoroutineExecutor implements Runtime, ExecutorImplementation
             foreach ($value as $itemValue) {
                 ++$index;
 
-                $itemPath   = $path;
+                $itemPath               = $path;
-                $itemPath[] = $index; // !!! use arrays COW semantics
+                $itemPath[]             = $index; // !!! use arrays COW semantics
+                $ctx->resolveInfo->path = $itemPath;
 
                 try {
                     if (! $this->completeValueFast($ctx, $itemType, $itemValue, $itemPath, $itemReturnValue)) {
@@ -639,7 +647,7 @@ class CoroutineExecutor implements Runtime, ExecutorImplementation
         } else {
             if ($type !== $this->schema->getType($type->name)) {
                 $hint = '';
-                if ($this->schema->getConfig()->typeLoader) {
+                if ($this->schema->getConfig()->typeLoader !== null) {
                     $hint = sprintf(
                         'Make sure that type loader returns the same instance as defined in %s.%s',
                         $ctx->type,
@@ -813,7 +821,10 @@ class CoroutineExecutor implements Runtime, ExecutorImplementation
                 } else {
                     $childContexts = [];
 
-                    foreach ($this->collector->collectFields($objectType, $ctx->shared->mergedSelectionSet ?? $this->mergeSelectionSets($ctx)) as $childShared) {
+                    foreach ($this->collector->collectFields(
+                        $objectType,
+                        $ctx->shared->mergedSelectionSet ?? $this->mergeSelectionSets($ctx)
+                    ) as $childShared) {
                         /** @var CoroutineContextShared $childShared */
 
                         $childPath   = $path;
@@ -897,7 +908,7 @@ class CoroutineExecutor implements Runtime, ExecutorImplementation
             return $this->schema->getType($value['__typename']);
         }
 
-        if ($abstractType instanceof InterfaceType && $this->schema->getConfig()->typeLoader) {
+        if ($abstractType instanceof InterfaceType && $this->schema->getConfig()->typeLoader !== null) {
             Warning::warnOnce(
                 sprintf(
                     'GraphQL Interface Type `%s` returned `null` from its `resolveType` function ' .
@@ -928,4 +939,14 @@ class CoroutineExecutor implements Runtime, ExecutorImplementation
 
         return $selectedType;
     }
+
+    /**
+     * @param mixed $value
+     *
+     * @return bool
+     */
+    private function isPromise($value)
+    {
+        return $value instanceof Promise || $this->promiseAdapter->isThenable($value);
+    }
 }

src/Language/AST/ListTypeNode.php

@@ -9,6 +9,6 @@ class ListTypeNode extends Node implements TypeNode
     /** @var string */
     public $kind = NodeKind::LIST_TYPE;
 
-    /** @var Node */
+    /** @var TypeNode */
     public $type;
 }

src/Language/AST/Location.php

@@ -59,6 +59,7 @@ class Location
         $tmp        = new static();
         $tmp->start = $start;
         $tmp->end   = $end;
+
         return $tmp;
     }
 
@@ -68,7 +69,7 @@ class Location
         $this->endToken   = $endToken;
         $this->source     = $source;
 
-        if (! $startToken || ! $endToken) {
+        if ($startToken === null || $endToken === null) {
             return;
         }
 

src/Language/AST/Node.php

@@ -40,7 +40,7 @@ abstract class Node
     public $loc;
 
     /**
-     * @param (string|NameNode|NodeList|SelectionSetNode|Location|null)[] $vars
+     * @param (NameNode|NodeList|SelectionSetNode|Location|string|int|bool|float|null)[] $vars
      */
     public function __construct(array $vars)
     {
@@ -106,7 +106,7 @@ abstract class Node
 
         $tmp = (array) $this;
 
-        if ($this->loc) {
+        if ($this->loc !== null) {
             $tmp['loc'] = [
                 'start' => $this->loc->start,
                 'end'   => $this->loc->end,
@@ -125,7 +125,7 @@ abstract class Node
             'kind' => $node->kind,
         ];
 
-        if ($node->loc) {
+        if ($node->loc !== null) {
             $result['loc'] = [
                 'start' => $node->loc->start,
                 'end'   => $node->loc->end,

src/Language/AST/NodeList.php

@@ -105,6 +105,7 @@ class NodeList implements ArrayAccess, IteratorAggregate, Countable
         if ($list instanceof self) {
             $list = $list->nodes;
         }
+
         return new NodeList(array_merge($this->nodes, $list));
     }
 
@@ -113,9 +114,8 @@ class NodeList implements ArrayAccess, IteratorAggregate, Countable
      */
     public function getIterator()
     {
-        $count = count($this->nodes);
+        foreach ($this->nodes as $key => $_) {
-        for ($i = 0; $i < $count; $i++) {
+            yield $this->offsetGet($key);
-            yield $this->offsetGet($i);
         }
     }
 

src/Language/AST/NonNullTypeNode.php

@@ -9,6 +9,6 @@ class NonNullTypeNode extends Node implements TypeNode
     /** @var string */
     public $kind = NodeKind::NON_NULL_TYPE;
 
-    /** @var NameNode | ListTypeNode */
+    /** @var NamedTypeNode | ListTypeNode */
     public $type;
 }

src/Language/Lexer.php

@@ -23,6 +23,22 @@ use function preg_match;
  */
 class Lexer
 {
+    private const TOKEN_BANG      = 33;
+    private const TOKEN_HASH      = 35;
+    private const TOKEN_DOLLAR    = 36;
+    private const TOKEN_AMP       = 38;
+    private const TOKEN_PAREN_L   = 40;
+    private const TOKEN_PAREN_R   = 41;
+    private const TOKEN_DOT       = 46;
+    private const TOKEN_COLON     = 58;
+    private const TOKEN_EQUALS    = 61;
+    private const TOKEN_AT        = 64;
+    private const TOKEN_BRACKET_L = 91;
+    private const TOKEN_BRACKET_R = 93;
+    private const TOKEN_BRACE_L   = 123;
+    private const TOKEN_PIPE      = 124;
+    private const TOKEN_BRACE_R   = 125;
+
     /** @var Source */
     public $source;
 
@@ -92,7 +108,8 @@ class Lexer
      */
     public function advance()
     {
-        $this->lastToken    = $this->token;
+        $this->lastToken = $this->token;
+
         return $this->token = $this->lookahead();
     }
 
@@ -131,44 +148,45 @@ class Lexer
         [, $code, $bytes] = $this->readChar(true);
 
         switch ($code) {
-            case 33: // !
+            case self::TOKEN_BANG:
                 return new Token(Token::BANG, $position, $position + 1, $line, $col, $prev);
-            case 35: // #
+            case self::TOKEN_HASH: // #
                 $this->moveStringCursor(-1, -1 * $bytes);
 
                 return $this->readComment($line, $col, $prev);
-            case 36: // $
+            case self::TOKEN_DOLLAR:
                 return new Token(Token::DOLLAR, $position, $position + 1, $line, $col, $prev);
-            case 38: // &
+            case self::TOKEN_AMP:
                 return new Token(Token::AMP, $position, $position + 1, $line, $col, $prev);
-            case 40: // (
+            case self::TOKEN_PAREN_L:
                 return new Token(Token::PAREN_L, $position, $position + 1, $line, $col, $prev);
-            case 41: // )
+            case self::TOKEN_PAREN_R:
                 return new Token(Token::PAREN_R, $position, $position + 1, $line, $col, $prev);
-            case 46: // .
+            case self::TOKEN_DOT: // .
                 [, $charCode1] = $this->readChar(true);
                 [, $charCode2] = $this->readChar(true);
 
-                if ($charCode1 === 46 && $charCode2 === 46) {
+                if ($charCode1 === self::TOKEN_DOT && $charCode2 === self::TOKEN_DOT) {
                     return new Token(Token::SPREAD, $position, $position + 3, $line, $col, $prev);
                 }
                 break;
-            case 58: // :
+            case self::TOKEN_COLON:
                 return new Token(Token::COLON, $position, $position + 1, $line, $col, $prev);
-            case 61: // =
+            case self::TOKEN_EQUALS:
                 return new Token(Token::EQUALS, $position, $position + 1, $line, $col, $prev);
-            case 64: // @
+            case self::TOKEN_AT:
                 return new Token(Token::AT, $position, $position + 1, $line, $col, $prev);
-            case 91: // [
+            case self::TOKEN_BRACKET_L:
                 return new Token(Token::BRACKET_L, $position, $position + 1, $line, $col, $prev);
-            case 93: // ]
+            case self::TOKEN_BRACKET_R:
                 return new Token(Token::BRACKET_R, $position, $position + 1, $line, $col, $prev);
-            case 123: // {
+            case self::TOKEN_BRACE_L:
                 return new Token(Token::BRACE_L, $position, $position + 1, $line, $col, $prev);
-            case 124: // |
+            case self::TOKEN_PIPE:
                 return new Token(Token::PIPE, $position, $position + 1, $line, $col, $prev);
-            case 125: // }
+            case self::TOKEN_BRACE_R:
                 return new Token(Token::BRACE_R, $position, $position + 1, $line, $col, $prev);
+
             // A-Z
             case 65:
             case 66:
@@ -227,6 +245,7 @@ class Lexer
             case 122:
                 return $this->moveStringCursor(-1, -1 * $bytes)
                     ->readName($line, $col, $prev);
+
             // -
             case 45:
                 // 0-9
@@ -242,6 +261,7 @@ class Lexer
             case 57:
                 return $this->moveStringCursor(-1, -1 * $bytes)
                     ->readNumber($line, $col, $prev);
+
             // "
             case 34:
                 [, $nextCode]     = $this->readChar();
@@ -294,11 +314,11 @@ class Lexer
         $start         = $this->position;
         [$char, $code] = $this->readChar();
 
-        while ($code && (
+        while ($code !== null && (
                 $code === 95 || // _
-                $code >= 48 && $code <= 57 || // 0-9
+                ($code >= 48 && $code <= 57) || // 0-9
-                $code >= 65 && $code <= 90 || // A-Z
+                ($code >= 65 && $code <= 90) || // A-Z
-                $code >= 97 && $code <= 122 // a-z
+                ($code >= 97 && $code <= 122) // a-z
             )) {
             $value        .= $char;
             [$char, $code] = $this->moveStringCursor(1, 1)->readChar();
@@ -564,10 +584,10 @@ class Lexer
                         $prev,
                         BlockString::value($value)
                     );
-                } else {
-                    // move cursor back to before the first quote
-                    $this->moveStringCursor(-2, -2);
                 }
+
+                // move cursor back to before the first quote
+                $this->moveStringCursor(-2, -2);
             }
 
             $this->assertValidBlockStringCharacterCode($code, $this->position);
@@ -675,7 +695,7 @@ class Lexer
         do {
             [$char, $code, $bytes] = $this->moveStringCursor(1, $bytes)->readChar();
             $value                .= $char;
-        } while ($code &&
+        } while ($code !== null &&
         // SourceCharacter but not LineTerminator
         ($code > 0x001F || $code === 0x0009)
         );

src/Language/Parser.php

@@ -439,7 +439,6 @@ class Parser
                 case 'mutation':
                 case 'subscription':
                     return $this->parseOperationDefinition();
-
                 case 'fragment':
                     return $this->parseFragmentDefinition();
             }
@@ -513,15 +512,15 @@ class Parser
      */
     private function parseVariableDefinitions()
     {
-        return $this->peek(Token::PAREN_L) ?
+        return $this->peek(Token::PAREN_L)
-            $this->many(
+            ? $this->many(
                 Token::PAREN_L,
                 function () {
                     return $this->parseVariableDefinition();
                 },
                 Token::PAREN_R
-            ) :
+            )
-            new NodeList([]);
+            : new NodeList([]);
     }
 
     /**
@@ -593,9 +592,9 @@ class Parser
      */
     private function parseSelection()
     {
-        return $this->peek(Token::SPREAD) ?
+        return $this->peek(Token::SPREAD)
-            $this->parseFragment() :
+            ? $this->parseFragment()
-            $this->parseField();
+            : $this->parseField();
     }
 
     /**
@@ -635,17 +634,17 @@ class Parser
      */
     private function parseArguments($isConst)
     {
-        $parseFn = $isConst ?
+        $parseFn = $isConst
-            function () {
+            ? function () {
                 return $this->parseConstArgument();
-            } :
+            }
-            function () {
+            : function () {
                 return $this->parseArgument();
             };
 
-        return $this->peek(Token::PAREN_L) ?
+        return $this->peek(Token::PAREN_L)
-            $this->many(Token::PAREN_L, $parseFn, Token::PAREN_R) :
+            ? $this->many(Token::PAREN_L, $parseFn, Token::PAREN_R)
-            new NodeList([]);
+            : new NodeList([]);
     }
 
     /**
@@ -827,7 +826,9 @@ class Parser
                         'value' => $token->value === 'true',
                         'loc'   => $this->loc($token),
                     ]);
-                } elseif ($token->value === 'null') {
+                }
+
+                if ($token->value === 'null') {
                     $this->lexer->advance();
 
                     return new NullValueNode([
@@ -1207,8 +1208,8 @@ class Parser
             do {
                 $types[] = $this->parseNamedType();
             } while ($this->skip(Token::AMP) ||
-            // Legacy support for the SDL?
+                // Legacy support for the SDL?
-            (! empty($this->lexer->options['allowLegacySDLImplementsInterfaces']) && $this->peek(Token::NAME))
+                (! empty($this->lexer->options['allowLegacySDLImplementsInterfaces']) && $this->peek(Token::NAME))
             );
         }
 
@@ -1544,7 +1545,8 @@ class Parser
                 Token::BRACE_L,
                 [$this, 'parseOperationTypeDefinition'],
                 Token::BRACE_R
-            ) : [];
+            )
+            : [];
         if (count($directives) === 0 && count($operationTypes) === 0) {
             $this->unexpected();
         }
@@ -1654,9 +1656,7 @@ class Parser
         $name       = $this->parseName();
         $directives = $this->parseDirectives(true);
         $types      = $this->parseUnionMemberTypes();
-        if (count($directives) === 0 &&
+        if (count($directives) === 0 && count($types) === 0) {
-            ! $types
-        ) {
             throw $this->unexpected();
         }
 

src/Language/Printer.php

@@ -28,6 +28,7 @@ use GraphQL\Language\AST\IntValueNode;
 use GraphQL\Language\AST\ListTypeNode;
 use GraphQL\Language\AST\ListValueNode;
 use GraphQL\Language\AST\NamedTypeNode;
+use GraphQL\Language\AST\NameNode;
 use GraphQL\Language\AST\Node;
 use GraphQL\Language\AST\NodeKind;
 use GraphQL\Language\AST\NonNullTypeNode;
@@ -47,6 +48,7 @@ use GraphQL\Language\AST\StringValueNode;
 use GraphQL\Language\AST\UnionTypeDefinitionNode;
 use GraphQL\Language\AST\UnionTypeExtensionNode;
 use GraphQL\Language\AST\VariableDefinitionNode;
+use GraphQL\Language\AST\VariableNode;
 use GraphQL\Utils\Utils;
 use function count;
 use function implode;
@@ -97,11 +99,11 @@ class Printer
             $ast,
             [
                 'leave' => [
-                    NodeKind::NAME => static function (Node $node) {
+                    NodeKind::NAME => static function (NameNode $node) {
                         return '' . $node->value;
                     },
 
-                    NodeKind::VARIABLE => static function ($node) {
+                    NodeKind::VARIABLE => static function (VariableNode $node) {
                         return '$' . $node->name;
                     },
 
@@ -115,6 +117,7 @@ class Printer
                         $varDefs      = $this->wrap('(', $this->join($node->variableDefinitions, ', '), ')');
                         $directives   = $this->join($node->directives, ' ');
                         $selectionSet = $node->selectionSet;
+
                         // Anonymous queries with no directives or variable definitions can use
                         // the query short form.
                         return ! $name && ! $directives && ! $varDefs && $op === 'query'

src/Language/Token.php

@@ -11,28 +11,28 @@ namespace GraphQL\Language;
 class Token
 {
     // Each kind of token.
-    const SOF          = '<SOF>';
+    public const SOF          = '<SOF>';
-    const EOF          = '<EOF>';
+    public const EOF          = '<EOF>';
-    const BANG         = '!';
+    public const BANG         = '!';
-    const DOLLAR       = '$';
+    public const DOLLAR       = '$';
-    const AMP          = '&';
+    public const AMP          = '&';
-    const PAREN_L      = '(';
+    public const PAREN_L      = '(';
-    const PAREN_R      = ')';
+    public const PAREN_R      = ')';
-    const SPREAD       = '...';
+    public const SPREAD       = '...';
-    const COLON        = ':';
+    public const COLON        = ':';
-    const EQUALS       = '=';
+    public const EQUALS       = '=';
-    const AT           = '@';
+    public const AT           = '@';
-    const BRACKET_L    = '[';
+    public const BRACKET_L    = '[';
-    const BRACKET_R    = ']';
+    public const BRACKET_R    = ']';
-    const BRACE_L      = '{';
+    public const BRACE_L      = '{';
-    const PIPE         = '|';
+    public const PIPE         = '|';
-    const BRACE_R      = '}';
+    public const BRACE_R      = '}';
-    const NAME         = 'Name';
+    public const NAME         = 'Name';
-    const INT          = 'Int';
+    public const INT          = 'Int';
-    const FLOAT        = 'Float';
+    public const FLOAT        = 'Float';
-    const STRING       = 'String';
+    public const STRING       = 'String';
-    const BLOCK_STRING = 'BlockString';
+    public const BLOCK_STRING = 'BlockString';
-    const COMMENT      = 'Comment';
+    public const COMMENT      = 'Comment';
 
     /**
      * The kind of Token (see one of constants above).
@@ -104,18 +104,15 @@ class Token
         $this->value  = $value;
     }
 
-    /**
+    public function getDescription() : string
-     * @return string
-     */
-    public function getDescription()
     {
-        return $this->kind . ($this->value ? ' "' . $this->value . '"' : '');
+        return $this->kind . ($this->value === null ? '' : ' "' . $this->value . '"');
     }
 
     /**
      * @return (string|int|null)[]
      */
-    public function toArray()
+    public function toArray() : array
     {
         return [
             'kind'   => $this->kind,

src/Language/Visitor.php

@@ -251,8 +251,18 @@ class Visitor
                 $inArray = $stack['inArray'];
                 $stack   = $stack['prev'];
             } else {
-                $key  = $parent !== null ? ($inArray ? $index : $keys[$index]) : $UNDEFINED;
+                $key  = $parent !== null
-                $node = $parent !== null ? ($parent instanceof NodeList || is_array($parent) ? $parent[$key] : $parent->{$key}) : $newRoot;
+                    ? ($inArray
+                        ? $index
+                        : $keys[$index]
+                    )
+                    : $UNDEFINED;
+                $node = $parent !== null
+                    ? ($parent instanceof NodeList || is_array($parent)
+                        ? $parent[$key]
+                        : $parent->{$key}
+                    )
+                    : $newRoot;
                 if ($node === null || $node === $UNDEFINED) {
                     continue;
                 }

src/Schema.php

@@ -1,22 +0,0 @@
-<?php
-
-declare(strict_types=1);
-
-namespace GraphQL;
-
-use function trigger_error;
-use const E_USER_DEPRECATED;
-
-trigger_error(
-    'GraphQL\Schema is moved to GraphQL\Type\Schema',
-    E_USER_DEPRECATED
-);
-
-/**
- * Schema Definition
- *
- * @deprecated moved to GraphQL\Type\Schema
- */
-class Schema extends \GraphQL\Type\Schema
-{
-}

src/Server/Helper.php

@@ -73,10 +73,14 @@ class Helper
             }
 
             if (stripos($contentType, 'application/graphql') !== false) {
-                $rawBody    = $readRawBodyFn ? $readRawBodyFn() : $this->readRawBody();
+                $rawBody    = $readRawBodyFn
+                    ? $readRawBodyFn()
+                    : $this->readRawBody();
                 $bodyParams = ['query' => $rawBody ?: ''];
             } elseif (stripos($contentType, 'application/json') !== false) {
-                $rawBody    = $readRawBodyFn ? $readRawBodyFn() : $this->readRawBody();
+                $rawBody    = $readRawBodyFn ?
+                    $readRawBodyFn()
+                    : $this->readRawBody();
                 $bodyParams = json_decode($rawBody ?: '', true);
 
                 if (json_last_error()) {
@@ -272,7 +276,9 @@ class Helper
                 );
             }
 
-            $doc = $op->queryId ? $this->loadPersistedQuery($config, $op) : $op->query;
+            $doc = $op->queryId
+                ? $this->loadPersistedQuery($config, $op)
+                : $op->query;
 
             if (! $doc instanceof DocumentNode) {
                 $doc = Parser::parse($doc);
@@ -385,13 +391,13 @@ class Helper
      */
     private function resolveRootValue(ServerConfig $config, OperationParams $params, DocumentNode $doc, $operationType)
     {
-        $root = $config->getRootValue();
+        $rootValue = $config->getRootValue();
 
-        if (is_callable($root)) {
+        if (is_callable($rootValue)) {
-            $root = $root($params, $doc, $operationType);
+            $rootValue = $rootValue($params, $doc, $operationType);
         }
 
-        return $root;
+        return $rootValue;
     }
 
     /**

src/Server/OperationParams.php

@@ -9,6 +9,7 @@ use function is_string;
 use function json_decode;
 use function json_last_error;
 use const CASE_LOWER;
+use const JSON_ERROR_NONE;
 
 /**
  * Structure representing parsed HTTP parameters for GraphQL operation
@@ -46,6 +47,12 @@ class OperationParams
      */
     public $variables;
 
+    /**
+     * @api
+     * @var mixed[]|null
+     */
+    public $extensions;
+
     /** @var mixed[] */
     private $originalInput;
 
@@ -56,13 +63,10 @@ class OperationParams
      * Creates an instance from given array
      *
      * @param mixed[] $params
-     * @param bool    $readonly
-     *
-     * @return OperationParams
      *
      * @api
      */
-    public static function create(array $params, $readonly = false)
+    public static function create(array $params, bool $readonly = false) : OperationParams
     {
         $instance = new static();
 
@@ -76,24 +80,38 @@ class OperationParams
             'id' => null, // alias to queryid
             'operationname' => null,
             'variables' => null,
+            'extensions' => null,
         ];
 
         if ($params['variables'] === '') {
             $params['variables'] = null;
         }
 
-        if (is_string($params['variables'])) {
+        // Some parameters could be provided as serialized JSON.
-            $tmp = json_decode($params['variables'], true);
+        foreach (['extensions', 'variables'] as $param) {
-            if (! json_last_error()) {
+            if (! is_string($params[$param])) {
-                $params['variables'] = $tmp;
+                continue;
             }
+
+            $tmp = json_decode($params[$param], true);
+            if (json_last_error() !== JSON_ERROR_NONE) {
+                continue;
+            }
+
+            $params[$param] = $tmp;
         }
 
-        $instance->query     = $params['query'];
+        $instance->query      = $params['query'];
-        $instance->queryId   = $params['queryid'] ?: $params['documentid'] ?: $params['id'];
+        $instance->queryId    = $params['queryid'] ?: $params['documentid'] ?: $params['id'];
-        $instance->operation = $params['operationname'];
+        $instance->operation  = $params['operationname'];
-        $instance->variables = $params['variables'];
+        $instance->variables  = $params['variables'];
-        $instance->readOnly  = (bool) $readonly;
+        $instance->extensions = $params['extensions'];
+        $instance->readOnly   = $readonly;
+
+        // Apollo server/client compatibility: look for the queryid in extensions
+        if (isset($instance->extensions['persistedQuery']['sha256Hash']) && empty($instance->query) && empty($instance->queryId)) {
+            $instance->queryId = $instance->extensions['persistedQuery']['sha256Hash'];
+        }
 
         return $instance;
     }

src/Server/ServerConfig.php

@@ -225,15 +225,11 @@ class ServerConfig
     /**
      * Allow batching queries (disabled by default)
      *
-     * @param bool $enableBatching
-     *
-     * @return self
-     *
      * @api
      */
-    public function setQueryBatching($enableBatching)
+    public function setQueryBatching(bool $enableBatching) : self
     {
-        $this->queryBatching = (bool) $enableBatching;
+        $this->queryBatching = $enableBatching;
 
         return $this;
     }

src/Server/StandardServer.php

@@ -151,6 +151,7 @@ class StandardServer
         StreamInterface $writableBodyStream
     ) {
         $result = $this->executePsrRequest($request);
+
         return $this->helper->toPsrResponse($result, $response, $writableBodyStream);
     }
 
@@ -165,6 +166,7 @@ class StandardServer
     public function executePsrRequest(ServerRequestInterface $request)
     {
         $parsedBody = $this->helper->parsePsrRequest($request);
+
         return $this->executeRequest($parsedBody);
     }
 

src/Type/Definition/BooleanType.php

@@ -11,9 +11,6 @@ use GraphQL\Language\AST\Node;
 use GraphQL\Utils\Utils;
 use function is_bool;
 
-/**
- * Class BooleanType
- */
 class BooleanType extends ScalarType
 {
     /** @var string */
@@ -23,11 +20,14 @@ class BooleanType extends ScalarType
     public $description = 'The `Boolean` scalar type represents `true` or `false`.';
 
     /**
-     * @param mixed $value
+     * Coerce the given value to a boolean.
      *
-     * @return bool
+     * The GraphQL spec leaves this up to the implementations, so we just do what
+     * PHP does natively to make this intuitive for developers.
+     *
+     * @param mixed $value
      */
-    public function serialize($value)
+    public function serialize($value) : bool
     {
         return (bool) $value;
     }
@@ -58,11 +58,11 @@ class BooleanType extends ScalarType
      */
     public function parseLiteral($valueNode, ?array $variables = null)
     {
-        if ($valueNode instanceof BooleanValueNode) {
+        if (! $valueNode instanceof BooleanValueNode) {
-            return (bool) $valueNode->value;
+            // Intentionally without message, as all information already in wrapped Exception
+            throw new Exception();
         }
 
-        // Intentionally without message, as all information already in wrapped Exception
+        return $valueNode->value;
-        throw new Exception();
     }
 }

src/Type/Definition/CustomScalarType.php

@@ -12,9 +12,6 @@ use function call_user_func;
 use function is_callable;
 use function sprintf;
 
-/**
- * Class CustomScalarType
- */
 class CustomScalarType extends ScalarType
 {
     /**

src/Type/Definition/Directive.php

@@ -8,24 +8,19 @@ use GraphQL\Language\AST\DirectiveDefinitionNode;
 use GraphQL\Language\DirectiveLocation;
 use GraphQL\Utils\Utils;
 use function array_key_exists;
-use function array_keys;
-use function in_array;
 use function is_array;
 
-/**
- * Class Directive
- */
 class Directive
 {
     public const DEFAULT_DEPRECATION_REASON = 'No longer supported';
 
-    const INCLUDE_NAME         = 'include';
+    public const INCLUDE_NAME         = 'include';
-    const IF_ARGUMENT_NAME     = 'if';
+    public const IF_ARGUMENT_NAME     = 'if';
-    const SKIP_NAME            = 'skip';
+    public const SKIP_NAME            = 'skip';
-    const DEPRECATED_NAME      = 'deprecated';
+    public const DEPRECATED_NAME      = 'deprecated';
-    const REASON_ARGUMENT_NAME = 'reason';
+    public const REASON_ARGUMENT_NAME = 'reason';
 
-    /** @var Directive[] */
+    /** @var Directive[]|null */
     public static $internalDirectives;
 
     // Schema Definitions
@@ -40,7 +35,7 @@ class Directive
     public $locations;
 
     /** @var FieldArgument[] */
-    public $args;
+    public $args = [];
 
     /** @var DirectiveDefinitionNode|null */
     public $astNode;
@@ -80,15 +75,16 @@ class Directive
     public static function includeDirective()
     {
         $internal = self::getInternalDirectives();
+
         return $internal['include'];
     }
 
     /**
      * @return Directive[]
      */
-    public static function getInternalDirectives()
+    public static function getInternalDirectives() : array
     {
-        if (! self::$internalDirectives) {
+        if (self::$internalDirectives === null) {
             self::$internalDirectives = [
                 'include'    => new self([
                     'name'        => self::INCLUDE_NAME,
@@ -140,24 +136,30 @@ class Directive
                 ]),
             ];
         }
+
         return self::$internalDirectives;
     }
+
     /**
      * @return Directive
      */
     public static function skipDirective()
     {
         $internal = self::getInternalDirectives();
+
         return $internal['skip'];
     }
+
     /**
      * @return Directive
      */
     public static function deprecatedDirective()
     {
         $internal = self::getInternalDirectives();
+
         return $internal['deprecated'];
     }
+
     /**
      * @return bool
      */

src/Type/Definition/EnumType.php

@@ -19,10 +19,7 @@ use function is_int;
 use function is_string;
 use function sprintf;
 
-/**
+class EnumType extends Type implements InputType, OutputType, LeafType, NullableType, NamedType
- * Class EnumType
- */
-class EnumType extends Type implements InputType, OutputType, LeafType, NamedType
 {
     /** @var EnumTypeDefinitionNode|null */
     public $astNode;
@@ -33,7 +30,7 @@ class EnumType extends Type implements InputType, OutputType, LeafType, NamedTyp
     /** @var MixedStore<mixed, EnumValueDefinition> */
     private $valueLookup;
 
-    /** @var \ArrayObject<string, EnumValueDefinition> */
+    /** @var ArrayObject<string, EnumValueDefinition> */
     private $nameLookup;
 
     /** @var EnumTypeExtensionNode[] */
@@ -71,7 +68,7 @@ class EnumType extends Type implements InputType, OutputType, LeafType, NamedTyp
     }
 
     /**
-     * @return \ArrayObject<string, EnumValueDefinition>
+     * @return ArrayObject<string, EnumValueDefinition>
      */
     private function getNameLookup()
     {

src/Type/Definition/EnumValueDefinition.php

@@ -6,9 +6,6 @@ namespace GraphQL\Type\Definition;
 
 use GraphQL\Language\AST\EnumValueDefinitionNode;
 
-/**
- * Class EnumValueDefinition
- */
 class EnumValueDefinition
 {
     /** @var string */

src/Type/Definition/FieldArgument.php

@@ -11,9 +11,6 @@ use function is_array;
 use function is_string;
 use function sprintf;
 
-/**
- * Class FieldArgument
- */
 class FieldArgument
 {
     /** @var string */

src/Type/Definition/FieldDefinition.php

@@ -81,7 +81,7 @@ class FieldDefinition
 
         $this->config = $config;
 
-        $this->complexityFn = $config['complexity'] ?? static::DEFAULT_COMPLEXITY_FN;
+        $this->complexityFn = $config['complexity'] ?? self::DEFAULT_COMPLEXITY_FN;
     }
 
     public static function defineFieldMap(Type $type, $fields)

src/Type/Definition/FloatType.php

@@ -12,9 +12,6 @@ use GraphQL\Language\AST\Node;
 use GraphQL\Utils\Utils;
 use function is_numeric;
 
-/**
- * Class FloatType
- */
 class FloatType extends ScalarType
 {
     /** @var string */

src/Type/Definition/InputObjectType.php

@@ -15,10 +15,7 @@ use function is_callable;
 use function is_string;
 use function sprintf;
 
-/**
+class InputObjectType extends Type implements InputType, NullableType, NamedType
- * Class InputObjectType
- */
-class InputObjectType extends Type implements InputType, NamedType
 {
     /** @var InputObjectTypeDefinitionNode|null */
     public $astNode;
@@ -72,7 +69,9 @@ class InputObjectType extends Type implements InputType, NamedType
         if ($this->fields === null) {
             $this->fields = [];
             $fields       = $this->config['fields'] ?? [];
-            $fields       = is_callable($fields) ? call_user_func($fields) : $fields;
+            $fields       = is_callable($fields)
+                ? call_user_func($fields)
+                : $fields;
 
             if (! is_array($fields)) {
                 throw new InvariantViolation(

src/Type/Definition/IntType.php

@@ -14,9 +14,6 @@ use function intval;
 use function is_bool;
 use function is_numeric;
 
-/**
- * Class IntType
- */
 class IntType extends ScalarType
 {
     // As per the GraphQL Spec, Integers are only treated as valid when a valid

src/Type/Definition/InterfaceType.php

@@ -12,10 +12,7 @@ use function is_callable;
 use function is_string;
 use function sprintf;
 
-/**
+class InterfaceType extends Type implements AbstractType, OutputType, CompositeType, NullableType, NamedType
- * Class InterfaceType
- */
-class InterfaceType extends Type implements AbstractType, OutputType, CompositeType, NamedType
 {
     /** @var InterfaceTypeDefinitionNode|null */
     public $astNode;
@@ -107,7 +104,7 @@ class InterfaceType extends Type implements AbstractType, OutputType, CompositeT
      * @param object  $objectValue
      * @param mixed[] $context
      *
-     * @return callable|null
+     * @return Type|null
      */
     public function resolveType($objectValue, $context, ResolveInfo $info)
     {

src/Type/Definition/ListOfType.php

@@ -4,10 +4,7 @@ declare(strict_types=1);
 
 namespace GraphQL\Type\Definition;
 
-/**
+class ListOfType extends Type implements WrappingType, OutputType, NullableType, InputType
- * Class ListOfType
- */
-class ListOfType extends Type implements WrappingType, OutputType, InputType
 {
     /** @var ObjectType|InterfaceType|UnionType|ScalarType|InputObjectType|EnumType */
     public $ofType;
@@ -20,15 +17,9 @@ class ListOfType extends Type implements WrappingType, OutputType, InputType
         $this->ofType = Type::assertType($type);
     }
 
-    /**
+    public function toString() : string
-     * @return string
-     */
-    public function toString()
     {
-        $type = $this->ofType;
+        return '[' . $this->ofType->toString() . ']';
-        $str  = $type instanceof Type ? $type->toString() : (string) $type;
-
-        return '[' . $str . ']';
     }
 
     /**
@@ -40,6 +31,8 @@ class ListOfType extends Type implements WrappingType, OutputType, InputType
     {
         $type = $this->ofType;
 
-        return $recurse && $type instanceof WrappingType ? $type->getWrappedType($recurse) : $type;
+        return $recurse && $type instanceof WrappingType
+            ? $type->getWrappedType($recurse)
+            : $type;
     }
 }

src/Type/Definition/NonNull.php

@@ -4,22 +4,15 @@ declare(strict_types=1);
 
 namespace GraphQL\Type\Definition;
 
-use Exception;
-use GraphQL\Error\InvariantViolation;
 use GraphQL\Utils\Utils;
 
-/**
- * Class NonNull
- */
 class NonNull extends Type implements WrappingType, OutputType, InputType
 {
-    /** @var ObjectType|InterfaceType|UnionType|ScalarType|InputObjectType|EnumType|ListOfType */
+    /** @var NullableType */
     private $ofType;
 
     /**
-     * @param callable|Type $type
+     * @param NullableType $type
-     *
-     * @throws Exception
      */
     public function __construct($type)
     {
@@ -29,7 +22,7 @@ class NonNull extends Type implements WrappingType, OutputType, InputType
     /**
      * @param mixed $type
      *
-     * @return ObjectType|InterfaceType|UnionType|ScalarType|InputObjectType|EnumType|ListOfType
+     * @return NullableType
      */
     public static function assertNullableType($type)
     {
@@ -67,14 +60,14 @@ class NonNull extends Type implements WrappingType, OutputType, InputType
     /**
      * @param bool $recurse
      *
-     * @return ObjectType|InterfaceType|UnionType|ScalarType|InputObjectType|EnumType|ListOfType
+     * @return Type
-     *
-     * @throws InvariantViolation
      */
     public function getWrappedType($recurse = false)
     {
         $type = $this->ofType;
 
-        return $recurse && $type instanceof WrappingType ? $type->getWrappedType($recurse) : $type;
+        return $recurse && $type instanceof WrappingType
+            ? $type->getWrappedType($recurse)
+            : $type;
     }
 }

src/Type/Definition/NullableType.php

@@ -0,0 +1,20 @@
+<?php
+
+declare(strict_types=1);
+
+namespace GraphQL\Type\Definition;
+
+/*
+export type GraphQLNullableType =
+  | GraphQLScalarType
+  | GraphQLObjectType
+  | GraphQLInterfaceType
+  | GraphQLUnionType
+  | GraphQLEnumType
+  | GraphQLInputObjectType
+  | GraphQLList<any>;
+ */
+
+interface NullableType
+{
+}

src/Type/Definition/ObjectType.php

@@ -54,7 +54,7 @@ use function sprintf;
  *        }
  *     ]);
  */
-class ObjectType extends Type implements OutputType, CompositeType, NamedType
+class ObjectType extends Type implements OutputType, CompositeType, NullableType, NamedType
 {
     /** @var ObjectTypeDefinitionNode|null */
     public $astNode;
@@ -168,7 +168,7 @@ class ObjectType extends Type implements OutputType, CompositeType, NamedType
 
     private function getInterfaceMap()
     {
-        if (! $this->interfaceMap) {
+        if ($this->interfaceMap === null) {
             $this->interfaceMap = [];
             foreach ($this->getInterfaces() as $interface) {
                 $this->interfaceMap[$interface->name] = $interface;
@@ -185,7 +185,9 @@ class ObjectType extends Type implements OutputType, CompositeType, NamedType
     {
         if ($this->interfaces === null) {
             $interfaces = $this->config['interfaces'] ?? [];
-            $interfaces = is_callable($interfaces) ? call_user_func($interfaces) : $interfaces;
+            $interfaces = is_callable($interfaces)
+                ? call_user_func($interfaces)
+                : $interfaces;
 
             if ($interfaces !== null && ! is_array($interfaces)) {
                 throw new InvariantViolation(
@@ -200,19 +202,21 @@ class ObjectType extends Type implements OutputType, CompositeType, NamedType
     }
 
     /**
-     * @param mixed[]      $value
+     * @param mixed        $value
      * @param mixed[]|null $context
      *
      * @return bool|null
      */
     public function isTypeOf($value, $context, ResolveInfo $info)
     {
-        return isset($this->config['isTypeOf']) ? call_user_func(
+        return isset($this->config['isTypeOf'])
-            $this->config['isTypeOf'],
+            ? call_user_func(
-            $value,
+                $this->config['isTypeOf'],
-            $context,
+                $value,
-            $info
+                $context,
-        ) : null;
+                $info
+            )
+            : null;
     }
 
     /**

src/Type/Definition/QueryPlan.php

@@ -0,0 +1,242 @@
+<?php
+
+declare(strict_types=1);
+
+namespace GraphQL\Type\Definition;
+
+use GraphQL\Error\Error;
+use GraphQL\Executor\Values;
+use GraphQL\Language\AST\FieldNode;
+use GraphQL\Language\AST\FragmentDefinitionNode;
+use GraphQL\Language\AST\FragmentSpreadNode;
+use GraphQL\Language\AST\InlineFragmentNode;
+use GraphQL\Language\AST\SelectionSetNode;
+use GraphQL\Type\Schema;
+use function array_filter;
+use function array_key_exists;
+use function array_keys;
+use function array_merge;
+use function array_merge_recursive;
+use function array_unique;
+use function array_values;
+use function count;
+use function in_array;
+use function is_array;
+use function is_numeric;
+
+class QueryPlan
+{
+    /** @var string[][] */
+    private $types = [];
+
+    /** @var Schema */
+    private $schema;
+
+    /** @var mixed[] */
+    private $queryPlan = [];
+
+    /** @var mixed[] */
+    private $variableValues;
+
+    /** @var FragmentDefinitionNode[] */
+    private $fragments;
+
+    /**
+     * @param FieldNode[]              $fieldNodes
+     * @param mixed[]                  $variableValues
+     * @param FragmentDefinitionNode[] $fragments
+     */
+    public function __construct(ObjectType $parentType, Schema $schema, iterable $fieldNodes, array $variableValues, array $fragments)
+    {
+        $this->schema         = $schema;
+        $this->variableValues = $variableValues;
+        $this->fragments      = $fragments;
+        $this->analyzeQueryPlan($parentType, $fieldNodes);
+    }
+
+    /**
+     * @return mixed[]
+     */
+    public function queryPlan() : array
+    {
+        return $this->queryPlan;
+    }
+
+    /**
+     * @return string[]
+     */
+    public function getReferencedTypes() : array
+    {
+        return array_keys($this->types);
+    }
+
+    public function hasType(string $type) : bool
+    {
+        return count(array_filter($this->getReferencedTypes(), static function (string $referencedType) use ($type) {
+                return $type === $referencedType;
+        })) > 0;
+    }
+
+    /**
+     * @return string[]
+     */
+    public function getReferencedFields() : array
+    {
+        return array_values(array_unique(array_merge(...array_values($this->types))));
+    }
+
+    public function hasField(string $field) : bool
+    {
+        return count(array_filter($this->getReferencedFields(), static function (string $referencedField) use ($field) {
+            return $field === $referencedField;
+        })) > 0;
+    }
+
+    /**
+     * @return string[]
+     */
+    public function subFields(string $typename) : array
+    {
+        if (! array_key_exists($typename, $this->types)) {
+            return [];
+        }
+
+        return $this->types[$typename];
+    }
+
+    /**
+     * @param FieldNode[] $fieldNodes
+     */
+    private function analyzeQueryPlan(ObjectType $parentType, iterable $fieldNodes) : void
+    {
+        $queryPlan = [];
+        /** @var FieldNode $fieldNode */
+        foreach ($fieldNodes as $fieldNode) {
+            if (! $fieldNode->selectionSet) {
+                continue;
+            }
+
+            $type = $parentType->getField($fieldNode->name->value)->getType();
+            if ($type instanceof WrappingType) {
+                $type = $type->getWrappedType();
+            }
+
+            $subfields = $this->analyzeSelectionSet($fieldNode->selectionSet, $type);
+
+            $this->types[$type->name] = array_unique(array_merge(
+                array_key_exists($type->name, $this->types) ? $this->types[$type->name] : [],
+                array_keys($subfields)
+            ));
+
+            $queryPlan = array_merge_recursive(
+                $queryPlan,
+                $subfields
+            );
+        }
+
+        $this->queryPlan = $queryPlan;
+    }
+
+    /**
+     * @return mixed[]
+     *
+     * $parentType InterfaceType|ObjectType.
+     *
+     * @throws Error
+     */
+    private function analyzeSelectionSet(SelectionSetNode $selectionSet, Type $parentType) : array
+    {
+        $fields = [];
+        foreach ($selectionSet->selections as $selectionNode) {
+            if ($selectionNode instanceof FieldNode) {
+                $fieldName     = $selectionNode->name->value;
+                $type          = $parentType->getField($fieldName);
+                $selectionType = $type->getType();
+
+                $subfields = [];
+                if ($selectionNode->selectionSet) {
+                    $subfields = $this->analyzeSubFields($selectionType, $selectionNode->selectionSet);
+                }
+
+                $fields[$fieldName] = [
+                    'type' => $selectionType,
+                    'fields' => $subfields ?? [],
+                    'args' => Values::getArgumentValues($type, $selectionNode, $this->variableValues),
+                ];
+            } elseif ($selectionNode instanceof FragmentSpreadNode) {
+                $spreadName = $selectionNode->name->value;
+                if (isset($this->fragments[$spreadName])) {
+                    $fragment  = $this->fragments[$spreadName];
+                    $type      = $this->schema->getType($fragment->typeCondition->name->value);
+                    $subfields = $this->analyzeSubFields($type, $fragment->selectionSet);
+
+                    $fields = $this->arrayMergeDeep(
+                        $subfields,
+                        $fields
+                    );
+                }
+            } elseif ($selectionNode instanceof InlineFragmentNode) {
+                $type      = $this->schema->getType($selectionNode->typeCondition->name->value);
+                $subfields = $this->analyzeSubFields($type, $selectionNode->selectionSet);
+
+                $fields = $this->arrayMergeDeep(
+                    $subfields,
+                    $fields
+                );
+            }
+        }
+
+        return $fields;
+    }
+
+    /**
+     * @return mixed[]
+     */
+    private function analyzeSubFields(Type $type, SelectionSetNode $selectionSet) : array
+    {
+        if ($type instanceof WrappingType) {
+            $type = $type->getWrappedType();
+        }
+
+        $subfields = [];
+        if ($type instanceof ObjectType) {
+            $subfields                = $this->analyzeSelectionSet($selectionSet, $type);
+            $this->types[$type->name] = array_unique(array_merge(
+                array_key_exists($type->name, $this->types) ? $this->types[$type->name] : [],
+                array_keys($subfields)
+            ));
+        }
+
+        return $subfields;
+    }
+
+    /**
+     * similar to array_merge_recursive this merges nested arrays, but handles non array values differently
+     * while array_merge_recursive tries to merge non array values, in this implementation they will be overwritten
+     *
+     * @see https://stackoverflow.com/a/25712428
+     *
+     * @param mixed[] $array1
+     * @param mixed[] $array2
+     *
+     * @return mixed[]
+     */
+    private function arrayMergeDeep(array $array1, array $array2) : array
+    {
+        $merged = $array1;
+
+        foreach ($array2 as $key => & $value) {
+            if (is_numeric($key)) {
+                if (! in_array($value, $merged, true)) {
+                    $merged[] = $value;
+                }
+            } elseif (is_array($value) && isset($merged[$key]) && is_array($merged[$key])) {
+                $merged[$key] = $this->arrayMergeDeep($merged[$key], $value);
+            } else {
+                $merged[$key] = $value;
+            }
+        }
+
+        return $merged;
+    }
+}

src/Type/Definition/ResolveInfo.php

@@ -15,15 +15,16 @@ use function array_merge_recursive;
 
 /**
  * Structure containing information useful for field resolution process.
- * Passed as 3rd argument to every field resolver. See [docs on field resolving (data fetching)](data-fetching.md).
+ *
+ * Passed as 4th argument to every field resolver. See [docs on field resolving (data fetching)](data-fetching.md).
  */
 class ResolveInfo
 {
     /**
-     * The name of the field being resolved
+     * The name of the field being resolved.
      *
      * @api
-     * @var string|null
+     * @var string
      */
     public $fieldName;
 
@@ -31,12 +32,12 @@ class ResolveInfo
      * AST of all nodes referencing this field in the query.
      *
      * @api
-     * @var FieldNode[]|null
+     * @var FieldNode[]
      */
-    public $fieldNodes;
+    public $fieldNodes = [];
 
     /**
-     * Expected return type of the field being resolved
+     * Expected return type of the field being resolved.
      *
      * @api
      * @var ScalarType|ObjectType|InterfaceType|UnionType|EnumType|ListOfType|NonNull
@@ -44,47 +45,47 @@ class ResolveInfo
     public $returnType;
 
     /**
-     * Parent type of the field being resolved
+     * Parent type of the field being resolved.
      *
      * @api
-     * @var ObjectType|null
+     * @var ObjectType
      */
     public $parentType;
 
     /**
-     * Path to this field from the very root value
+     * Path to this field from the very root value.
      *
      * @api
-     * @var string[]
+     * @var string[][]
      */
     public $path;
 
     /**
-     * Instance of a schema used for execution
+     * Instance of a schema used for execution.
      *
      * @api
-     * @var Schema|null
+     * @var Schema
      */
     public $schema;
 
     /**
-     * AST of all fragments defined in query
+     * AST of all fragments defined in query.
      *
      * @api
-     * @var FragmentDefinitionNode[]|null
+     * @var FragmentDefinitionNode[]
      */
-    public $fragments;
+    public $fragments = [];
 
     /**
-     * Root value passed to query execution
+     * Root value passed to query execution.
      *
      * @api
-     * @var mixed|null
+     * @var mixed
      */
     public $rootValue;
 
     /**
-     * AST of operation definition node (query, mutation)
+     * AST of operation definition node (query, mutation).
      *
      * @api
      * @var OperationDefinitionNode|null
@@ -92,24 +93,35 @@ class ResolveInfo
     public $operation;
 
     /**
-     * Array of variables passed to query execution
+     * Array of variables passed to query execution.
      *
      * @api
-     * @var mixed[]|null
+     * @var mixed[]
      */
-    public $variableValues;
+    public $variableValues = [];
 
+    /** @var QueryPlan */
+    private $queryPlan;
+
+    /**
+     * @param FieldNode[]                                                               $fieldNodes
+     * @param ScalarType|ObjectType|InterfaceType|UnionType|EnumType|ListOfType|NonNull $returnType
+     * @param string[][]                                                                $path
+     * @param FragmentDefinitionNode[]                                                  $fragments
+     * @param mixed|null                                                                $rootValue
+     * @param mixed[]                                                                   $variableValues
+     */
     public function __construct(
         string $fieldName,
-        $fieldNodes,
+        iterable $fieldNodes,
         $returnType,
         ObjectType $parentType,
-        $path,
+        array $path,
         Schema $schema,
-        $fragments,
+        array $fragments,
         $rootValue,
         ?OperationDefinitionNode $operation,
-        $variableValues
+        array $variableValues
     ) {
         $this->fieldName      = $fieldName;
         $this->fieldNodes     = $fieldNodes;
@@ -125,7 +137,7 @@ class ResolveInfo
 
     /**
      * Helper method that returns names of all fields selected in query for
-     * $this->fieldName up to $depth levels
+     * $this->fieldName up to $depth levels.
      *
      * Example:
      * query MyQuery{
@@ -166,11 +178,30 @@ class ResolveInfo
 
         /** @var FieldNode $fieldNode */
         foreach ($this->fieldNodes as $fieldNode) {
-            $fields = array_merge_recursive($fields, $this->foldSelectionSet($fieldNode->selectionSet, $depth));
+            $fields = array_merge_recursive(
+                $fields,
+                $this->foldSelectionSet($fieldNode->selectionSet, $depth)
+            );
         }
 
         return $fields;
     }
+
+    public function lookAhead() : QueryPlan
+    {
+        if ($this->queryPlan === null) {
+            $this->queryPlan = new QueryPlan(
+                $this->parentType,
+                $this->schema,
+                $this->fieldNodes,
+                $this->variableValues,
+                $this->fragments
+            );
+        }
+
+        return $this->queryPlan;
+    }
+
     /**
      * @return bool[]
      */
@@ -199,6 +230,7 @@ class ResolveInfo
                 );
             }
         }
+
         return $fields;
     }
 }

src/Type/Definition/ScalarType.php

@@ -27,7 +27,7 @@ use function is_string;
  *     }
  * }
  */
-abstract class ScalarType extends Type implements OutputType, InputType, LeafType, NamedType
+abstract class ScalarType extends Type implements OutputType, InputType, LeafType, NullableType, NamedType
 {
     /** @var ScalarTypeDefinitionNode|null */
     public $astNode;

src/Type/Definition/StringType.php

@@ -14,9 +14,6 @@ use function is_object;
 use function is_scalar;
 use function method_exists;
 
-/**
- * Class StringType
- */
 class StringType extends ScalarType
 {
     /** @var string */

src/Type/Definition/Type.php

@@ -137,7 +137,7 @@ abstract class Type implements JsonSerializable
     }
 
     /**
-     * @param ObjectType|InterfaceType|UnionType|ScalarType|InputObjectType|EnumType|ListOfType $wrappedType
+     * @param NullableType $wrappedType
      *
      * @return NonNull
      *
@@ -194,6 +194,7 @@ abstract class Type implements JsonSerializable
     public static function getInternalTypes()
     {
         trigger_error(__METHOD__ . ' is deprecated. Use Type::getStandardTypes() instead', E_USER_DEPRECATED);
+
         return self::getStandardTypes();
     }
 
@@ -338,13 +339,15 @@ abstract class Type implements JsonSerializable
     /**
      * @param Type $type
      *
-     * @return ObjectType|InterfaceType|UnionType|ScalarType|InputObjectType|EnumType|ListOfType
+     * @return NullableType
      *
      * @api
      */
     public static function getNullableType($type)
     {
-        return $type instanceof NonNull ? $type->getWrappedType() : $type;
+        return $type instanceof NonNull
+            ? $type->getWrappedType()
+            : $type;
     }
 
     /**

src/Type/Definition/UnionType.php

@@ -14,10 +14,7 @@ use function is_callable;
 use function is_string;
 use function sprintf;
 
-/**
+class UnionType extends Type implements AbstractType, OutputType, CompositeType, NullableType, NamedType
- * Class UnionType
- */
-class UnionType extends Type implements AbstractType, OutputType, CompositeType, NamedType
 {
     /** @var UnionTypeDefinitionNode */
     public $astNode;

src/Type/Introspection.php

@@ -488,7 +488,9 @@ EOD;
                         'type'         => [
                             'type'    => Type::nonNull(self::_type()),
                             'resolve' => static function ($value) {
-                                return method_exists($value, 'getType') ? $value->getType() : $value->type;
+                                return method_exists($value, 'getType')
+                                    ? $value->getType()
+                                    : $value->type;
                             },
                         ],
                         'defaultValue' => [
@@ -693,7 +695,7 @@ EOD;
         return self::$map['__DirectiveLocation'];
     }
 
-    public static function schemaMetaFieldDef()
+    public static function schemaMetaFieldDef() : FieldDefinition
     {
         if (! isset(self::$map[self::SCHEMA_FIELD_NAME])) {
             self::$map[self::SCHEMA_FIELD_NAME] = FieldDefinition::create([
@@ -715,7 +717,7 @@ EOD;
         return self::$map[self::SCHEMA_FIELD_NAME];
     }
 
-    public static function typeMetaFieldDef()
+    public static function typeMetaFieldDef() : FieldDefinition
     {
         if (! isset(self::$map[self::TYPE_FIELD_NAME])) {
             self::$map[self::TYPE_FIELD_NAME] = FieldDefinition::create([
@@ -734,7 +736,7 @@ EOD;
         return self::$map[self::TYPE_FIELD_NAME];
     }
 
-    public static function typeNameMetaFieldDef()
+    public static function typeNameMetaFieldDef() : FieldDefinition
     {
         if (! isset(self::$map[self::TYPE_NAME_FIELD_NAME])) {
             self::$map[self::TYPE_NAME_FIELD_NAME] = FieldDefinition::create([

src/Type/SchemaConfig.php

@@ -42,7 +42,7 @@ class SchemaConfig
     /** @var Directive[] */
     public $directives;
 
-    /** @var callable */
+    /** @var callable|null */
     public $typeLoader;
 
     /** @var SchemaDefinitionNode */

src/Type/SchemaValidationContext.php

@@ -29,6 +29,7 @@ use GraphQL\Type\Definition\NonNull;
 use GraphQL\Type\Definition\ObjectType;
 use GraphQL\Type\Definition\Type;
 use GraphQL\Type\Definition\UnionType;
+use GraphQL\Type\Validation\InputObjectCircularRefs;
 use GraphQL\Utils\TypeComparators;
 use GraphQL\Utils\Utils;
 use function array_filter;
@@ -48,9 +49,13 @@ class SchemaValidationContext
     /** @var Schema */
     private $schema;
 
+    /** @var InputObjectCircularRefs */
+    private $inputObjectCircularRefs;
+
     public function __construct(Schema $schema)
     {
-        $this->schema = $schema;
+        $this->schema                  = $schema;
+        $this->inputObjectCircularRefs = new InputObjectCircularRefs($this);
     }
 
     /**
@@ -99,7 +104,7 @@ class SchemaValidationContext
      * @param string                                       $message
      * @param Node[]|Node|TypeNode|TypeDefinitionNode|null $nodes
      */
-    private function reportError($message, $nodes = null)
+    public function reportError($message, $nodes = null)
     {
         $nodes = array_filter($nodes && is_array($nodes) ? $nodes : [$nodes]);
         $this->addError(new Error($message, $nodes));
@@ -247,7 +252,7 @@ class SchemaValidationContext
             if (! $type instanceof NamedType) {
                 $this->reportError(
                     'Expected GraphQL named type but got: ' . Utils::printSafe($type) . '.',
-                    is_object($type) ? $type->astNode : null
+                    $type instanceof Type ? $type->astNode : null
                 );
                 continue;
             }
@@ -275,6 +280,9 @@ class SchemaValidationContext
             } elseif ($type instanceof InputObjectType) {
                 // Ensure Input Object fields are valid.
                 $this->validateInputFields($type);
+
+                // Ensure Input Objects do not contain non-nullable circular references
+                $this->inputObjectCircularRefs->validate($type);
             }
         }
     }
@@ -760,8 +768,9 @@ class SchemaValidationContext
             );
         }
 
-        return $union->astNode ?
+        return $union->astNode
-            $union->astNode->types : null;
+            ? $union->astNode->types
+            : null;
     }
 
     private function validateEnumValues(EnumType $enumType)
@@ -816,8 +825,9 @@ class SchemaValidationContext
             );
         }
 
-        return $enum->astNode ?
+        return $enum->astNode
-            $enum->astNode->values : null;
+            ? $enum->astNode->values
+            : null;
     }
 
     private function validateInputFields(InputObjectType $inputObj)

src/Type/Validation/InputObjectCircularRefs.php

@@ -0,0 +1,105 @@
+<?php
+
+declare(strict_types=1);
+
+namespace GraphQL\Type\Validation;
+
+use GraphQL\Language\AST\InputValueDefinitionNode;
+use GraphQL\Type\Definition\InputObjectField;
+use GraphQL\Type\Definition\InputObjectType;
+use GraphQL\Type\Definition\NonNull;
+use GraphQL\Type\SchemaValidationContext;
+use function array_map;
+use function array_pop;
+use function array_slice;
+use function count;
+use function implode;
+
+class InputObjectCircularRefs
+{
+    /** @var SchemaValidationContext */
+    private $schemaValidationContext;
+
+    /**
+     * Tracks already visited types to maintain O(N) and to ensure that cycles
+     * are not redundantly reported.
+     *
+     * @var InputObjectType[]
+     */
+    private $visitedTypes = [];
+
+    /** @var InputObjectField[] */
+    private $fieldPath = [];
+
+    /**
+     * Position in the type path.
+     *
+     * [string $typeName => int $index]
+     *
+     * @var int[]
+     */
+    private $fieldPathIndexByTypeName = [];
+
+    public function __construct(SchemaValidationContext $schemaValidationContext)
+    {
+        $this->schemaValidationContext = $schemaValidationContext;
+    }
+
+    /**
+     * This does a straight-forward DFS to find cycles.
+     * It does not terminate when a cycle was found but continues to explore
+     * the graph to find all possible cycles.
+     */
+    public function validate(InputObjectType $inputObj) : void
+    {
+        if (isset($this->visitedTypes[$inputObj->name])) {
+            return;
+        }
+
+        $this->visitedTypes[$inputObj->name]             = true;
+        $this->fieldPathIndexByTypeName[$inputObj->name] = count($this->fieldPath);
+
+        $fieldMap = $inputObj->getFields();
+        foreach ($fieldMap as $fieldName => $field) {
+            $type = $field->getType();
+
+            if ($type instanceof NonNull) {
+                $fieldType = $type->getWrappedType();
+
+                // If the type of the field is anything else then a non-nullable input object,
+                // there is no chance of an unbreakable cycle
+                if ($fieldType instanceof InputObjectType) {
+                    $this->fieldPath[] = $field;
+
+                    if (! isset($this->fieldPathIndexByTypeName[$fieldType->name])) {
+                        $this->validate($fieldType);
+                    } else {
+                        $cycleIndex = $this->fieldPathIndexByTypeName[$fieldType->name];
+                        $cyclePath  = array_slice($this->fieldPath, $cycleIndex);
+                        $fieldNames = array_map(
+                            static function (InputObjectField $field) : string {
+                                return $field->name;
+                            },
+                            $cyclePath
+                        );
+
+                        $this->schemaValidationContext->reportError(
+                            'Cannot reference Input Object "' . $fieldType->name . '" within itself '
+                            . 'through a series of non-null fields: "' . implode('.', $fieldNames) . '".',
+                            array_map(
+                                static function (InputObjectField $field) : ?InputValueDefinitionNode {
+                                    return $field->astNode;
+                                },
+                                $cyclePath
+                            )
+                        );
+                    }
+                }
+            }
+
+            array_pop($this->fieldPath);
+        }
+
+        unset($this->fieldPathIndexByTypeName[$inputObj->name]);
+    }
+}

src/Utils/AST.php

@@ -183,7 +183,7 @@ class AST
                     $valuesNodes[] = $itemNode;
                 }
 
-                return new ListValueNode(['values' => $valuesNodes]);
+                return new ListValueNode(['values' => new NodeList($valuesNodes)]);
             }
 
             return self::astFromValue($value, $itemType);
@@ -235,7 +235,7 @@ class AST
                 ]);
             }
 
-            return new ObjectValueNode(['fields' => $fieldNodes]);
+            return new ObjectValueNode(['fields' => new NodeList($fieldNodes)]);
         }
 
         if ($type instanceof ScalarType || $type instanceof EnumType) {
@@ -322,7 +322,7 @@ class AST
      *
      * @api
      */
-    public static function valueFromAST($valueNode, InputType $type, ?array $variables = null)
+    public static function valueFromAST($valueNode, Type $type, ?array $variables = null)
     {
         $undefined = Utils::undefined();
 
@@ -353,6 +353,7 @@ class AST
                 // No valid return value.
                 return $undefined;
             }
+
             // Note: we're not doing any checking that this variable is correct. We're
             // assuming that this query has been validated and the variable usage here
             // is of the correct type.

src/Utils/ASTDefinitionBuilder.php

@@ -17,7 +17,6 @@ use GraphQL\Language\AST\InterfaceTypeDefinitionNode;
 use GraphQL\Language\AST\ListTypeNode;
 use GraphQL\Language\AST\NamedTypeNode;
 use GraphQL\Language\AST\Node;
-use GraphQL\Language\AST\NodeKind;
 use GraphQL\Language\AST\NonNullTypeNode;
 use GraphQL\Language\AST\ObjectTypeDefinitionNode;
 use GraphQL\Language\AST\ScalarTypeDefinitionNode;
@@ -144,7 +143,8 @@ class ASTDefinitionBuilder
                 // Note: While this could make assertions to get the correctly typed
                 // value, that would throw immediately while type system validation
                 // with validateSchema() will produce more actionable results.
-                $type   = $this->internalBuildWrappedType($value->type);
+                $type = $this->internalBuildWrappedType($value->type);
+
                 $config = [
                     'name'        => $value->name->value,
                     'type'        => $type,
@@ -244,23 +244,20 @@ class ASTDefinitionBuilder
      *
      * @throws Error
      */
-    private function makeSchemaDef($def)
+    private function makeSchemaDef(Node $def)
     {
-        if (! $def) {
+        switch (true) {
-            throw new Error('def must be defined.');
+            case $def instanceof ObjectTypeDefinitionNode:
-        }
-        switch ($def->kind) {
-            case NodeKind::OBJECT_TYPE_DEFINITION:
                 return $this->makeTypeDef($def);
-            case NodeKind::INTERFACE_TYPE_DEFINITION:
+            case $def instanceof InterfaceTypeDefinitionNode:
                 return $this->makeInterfaceDef($def);
-            case NodeKind::ENUM_TYPE_DEFINITION:
+            case $def instanceof EnumTypeDefinitionNode:
                 return $this->makeEnumDef($def);
-            case NodeKind::UNION_TYPE_DEFINITION:
+            case $def instanceof UnionTypeDefinitionNode:
                 return $this->makeUnionDef($def);
-            case NodeKind::SCALAR_TYPE_DEFINITION:
+            case $def instanceof ScalarTypeDefinitionNode:
                 return $this->makeScalarDef($def);
-            case NodeKind::INPUT_OBJECT_TYPE_DEFINITION:
+            case $def instanceof InputObjectTypeDefinitionNode:
                 return $this->makeInputObjectDef($def);
             default:
                 throw new Error(sprintf('Type kind of %s not supported.', $def->kind));
@@ -397,8 +394,8 @@ class ASTDefinitionBuilder
                     function ($typeNode) {
                         return $this->buildType($typeNode);
                     }
-                ) :
+                )
-                [],
+                : [],
             'astNode'     => $def,
         ]);
     }
@@ -430,62 +427,48 @@ class ASTDefinitionBuilder
     }
 
     /**
-     * @param ObjectTypeDefinitionNode|InterfaceTypeDefinitionNode|EnumTypeExtensionNode|ScalarTypeDefinitionNode|InputObjectTypeDefinitionNode $def
+     * @param mixed[] $config
-     * @param mixed[]                                                                                                                           $config
      *
      * @return CustomScalarType|EnumType|InputObjectType|InterfaceType|ObjectType|UnionType
      *
      * @throws Error
      */
-    private function makeSchemaDefFromConfig($def, array $config)
+    private function makeSchemaDefFromConfig(Node $def, array $config)
     {
-        if (! $def) {
+        switch (true) {
-            throw new Error('def must be defined.');
+            case $def instanceof ObjectTypeDefinitionNode:
-        }
-        switch ($def->kind) {
-            case NodeKind::OBJECT_TYPE_DEFINITION:
                 return new ObjectType($config);
-            case NodeKind::INTERFACE_TYPE_DEFINITION:
+            case $def instanceof InterfaceTypeDefinitionNode:
                 return new InterfaceType($config);
-            case NodeKind::ENUM_TYPE_DEFINITION:
+            case $def instanceof EnumTypeDefinitionNode:
                 return new EnumType($config);
-            case NodeKind::UNION_TYPE_DEFINITION:
+            case $def instanceof UnionTypeDefinitionNode:
                 return new UnionType($config);
-            case NodeKind::SCALAR_TYPE_DEFINITION:
+            case $def instanceof ScalarTypeDefinitionNode:
                 return new CustomScalarType($config);
-            case NodeKind::INPUT_OBJECT_TYPE_DEFINITION:
+            case $def instanceof InputObjectTypeDefinitionNode:
                 return new InputObjectType($config);
             default:
                 throw new Error(sprintf('Type kind of %s not supported.', $def->kind));
         }
     }
 
-    /**
+    private function getNamedTypeNode(TypeNode $typeNode) : TypeNode
-     * @param TypeNode|ListTypeNode|NonNullTypeNode $typeNode
-     *
-     * @return TypeNode
-     */
-    private function getNamedTypeNode(TypeNode $typeNode)
     {
         $namedType = $typeNode;
-        while ($namedType->kind === NodeKind::LIST_TYPE || $namedType->kind === NodeKind::NON_NULL_TYPE) {
+        while ($namedType instanceof ListTypeNode || $namedType instanceof NonNullTypeNode) {
             $namedType = $namedType->type;
         }
 
         return $namedType;
     }
 
-    /**
+    private function buildWrappedType(Type $innerType, TypeNode $inputTypeNode) : Type
-     * @param TypeNode|ListTypeNode|NonNullTypeNode $inputTypeNode
-     *
-     * @return Type
-     */
-    private function buildWrappedType(Type $innerType, TypeNode $inputTypeNode)
     {
-        if ($inputTypeNode->kind === NodeKind::LIST_TYPE) {
+        if ($inputTypeNode instanceof ListTypeNode) {
             return Type::listOf($this->buildWrappedType($innerType, $inputTypeNode->type));
         }
-        if ($inputTypeNode->kind === NodeKind::NON_NULL_TYPE) {
+        if ($inputTypeNode instanceof NonNullTypeNode) {
             $wrappedType = $this->buildWrappedType($innerType, $inputTypeNode->type);
 
             return Type::nonNull(NonNull::assertNullableType($wrappedType));

src/Utils/BreakingChangesFinder.php

@@ -112,27 +112,31 @@ class BreakingChangesFinder
      * @return string[][]
      */
     public static function findTypesThatChangedKind(
-        Schema $oldSchema,
+        Schema $schemaA,
-        Schema $newSchema
+        Schema $schemaB
-    ) {
+    ) : iterable {
-        $oldTypeMap = $oldSchema->getTypeMap();
+        $schemaATypeMap = $schemaA->getTypeMap();
-        $newTypeMap = $newSchema->getTypeMap();
+        $schemaBTypeMap = $schemaB->getTypeMap();
 
         $breakingChanges = [];
-        foreach ($oldTypeMap as $typeName => $oldType) {
+        foreach ($schemaATypeMap as $typeName => $schemaAType) {
-            if (! isset($newTypeMap[$typeName])) {
+            if (! isset($schemaBTypeMap[$typeName])) {
                 continue;
             }
-            $newType = $newTypeMap[$typeName];
+            $schemaBType = $schemaBTypeMap[$typeName];
-            if ($oldType instanceof $newType) {
+            if ($schemaAType instanceof $schemaBType) {
                 continue;
             }
 
-            $oldTypeKindName   = self::typeKindName($oldType);
+            if ($schemaBType instanceof $schemaAType) {
-            $newTypeKindName   = self::typeKindName($newType);
+                continue;
-            $breakingChanges[] = [
+            }
+
+            $schemaATypeKindName = self::typeKindName($schemaAType);
+            $schemaBTypeKindName = self::typeKindName($schemaBType);
+            $breakingChanges[]   = [
                 'type'        => self::BREAKING_CHANGE_TYPE_CHANGED_KIND,
-                'description' => "${typeName} changed from ${oldTypeKindName} to ${newTypeKindName}.",
+                'description' => "${typeName} changed from ${schemaATypeKindName} to ${schemaBTypeKindName}.",
             ];
         }
 
@@ -527,12 +531,12 @@ class BreakingChangesFinder
                         ];
                     }
                     // Check if a non-null arg was added to the field
-                    foreach ($newTypeFields[$fieldName]->args as $newArgDef) {
+                    foreach ($newTypeFields[$fieldName]->args as $newTypeFieldArgDef) {
                         $oldArgs   = $oldTypeFields[$fieldName]->args;
                         $oldArgDef = Utils::find(
                             $oldArgs,
-                            static function ($arg) use ($newArgDef) {
+                            static function ($arg) use ($newTypeFieldArgDef) {
-                                return $arg->name === $newArgDef->name;
+                                return $arg->name === $newTypeFieldArgDef->name;
                             }
                         );
 
@@ -541,8 +545,8 @@ class BreakingChangesFinder
                         }
 
                         $newTypeName = $newType->name;
-                        $newArgName  = $newArgDef->name;
+                        $newArgName  = $newTypeFieldArgDef->name;
-                        if ($newArgDef->getType() instanceof NonNull) {
+                        if ($newTypeFieldArgDef->getType() instanceof NonNull) {
                             $breakingChanges[] = [
                                 'type'        => self::BREAKING_CHANGE_NON_NULL_ARG_ADDED,
                                 'description' => "A non-null arg ${newArgName} on ${newTypeName}.${fieldName} was added",
@@ -664,7 +668,7 @@ class BreakingChangesFinder
     {
         $removedArgs = [];
         $newArgMap   = self::getArgumentMapForDirective($newDirective);
-        foreach ((array) $oldDirective->args as $arg) {
+        foreach ($oldDirective->args as $arg) {
             if (isset($newArgMap[$arg->name])) {
                 continue;
             }
@@ -723,7 +727,7 @@ class BreakingChangesFinder
     {
         $addedArgs = [];
         $oldArgMap = self::getArgumentMapForDirective($oldDirective);
-        foreach ((array) $newDirective->args as $arg) {
+        foreach ($newDirective->args as $arg) {
             if (isset($oldArgMap[$arg->name])) {
                 continue;
             }

src/Utils/BuildSchema.php

@@ -5,10 +5,16 @@ declare(strict_types=1);
 namespace GraphQL\Utils;
 
 use GraphQL\Error\Error;
+use GraphQL\Language\AST\DirectiveDefinitionNode;
 use GraphQL\Language\AST\DocumentNode;
+use GraphQL\Language\AST\EnumTypeDefinitionNode;
+use GraphQL\Language\AST\InputObjectTypeDefinitionNode;
+use GraphQL\Language\AST\InterfaceTypeDefinitionNode;
 use GraphQL\Language\AST\Node;
-use GraphQL\Language\AST\NodeKind;
+use GraphQL\Language\AST\ObjectTypeDefinitionNode;
+use GraphQL\Language\AST\ScalarTypeDefinitionNode;
 use GraphQL\Language\AST\SchemaDefinitionNode;
+use GraphQL\Language\AST\UnionTypeDefinitionNode;
 use GraphQL\Language\Parser;
 use GraphQL\Language\Source;
 use GraphQL\Type\Definition\Directive;
@@ -95,39 +101,38 @@ class BuildSchema
 
     public function buildSchema()
     {
-        /** @var SchemaDefinitionNode $schemaDef */
         $schemaDef     = null;
         $typeDefs      = [];
         $this->nodeMap = [];
         $directiveDefs = [];
-        foreach ($this->ast->definitions as $d) {
+        foreach ($this->ast->definitions as $definition) {
-            switch ($d->kind) {
+            switch (true) {
-                case NodeKind::SCHEMA_DEFINITION:
+                case $definition instanceof SchemaDefinitionNode:
-                    if ($schemaDef) {
+                    if ($schemaDef !== null) {
                         throw new Error('Must provide only one schema definition.');
                     }
-                    $schemaDef = $d;
+                    $schemaDef = $definition;
                     break;
-                case NodeKind::SCALAR_TYPE_DEFINITION:
+                case $definition instanceof ScalarTypeDefinitionNode:
-                case NodeKind::OBJECT_TYPE_DEFINITION:
+                case $definition instanceof ObjectTypeDefinitionNode:
-                case NodeKind::INTERFACE_TYPE_DEFINITION:
+                case $definition instanceof InterfaceTypeDefinitionNode:
-                case NodeKind::ENUM_TYPE_DEFINITION:
+                case $definition instanceof EnumTypeDefinitionNode:
-                case NodeKind::UNION_TYPE_DEFINITION:
+                case $definition instanceof UnionTypeDefinitionNode:
-                case NodeKind::INPUT_OBJECT_TYPE_DEFINITION:
+                case $definition instanceof InputObjectTypeDefinitionNode:
-                    $typeName = $d->name->value;
+                    $typeName = $definition->name->value;
                     if (! empty($this->nodeMap[$typeName])) {
                         throw new Error(sprintf('Type "%s" was defined more than once.', $typeName));
                     }
-                    $typeDefs[]               = $d;
+                    $typeDefs[]               = $definition;
-                    $this->nodeMap[$typeName] = $d;
+                    $this->nodeMap[$typeName] = $definition;
                     break;
-                case NodeKind::DIRECTIVE_DEFINITION:
+                case $definition instanceof DirectiveDefinitionNode:
-                    $directiveDefs[] = $d;
+                    $directiveDefs[] = $definition;
                     break;
             }
         }
 
-        $operationTypes = $schemaDef
+        $operationTypes = $schemaDef !== null
             ? $this->getOperationTypes($schemaDef)
             : [
                 'query'        => isset($this->nodeMap['Query']) ? 'Query' : null,
@@ -154,9 +159,10 @@ class BuildSchema
         // If specified directives were not explicitly declared, add them.
         $skip = array_reduce(
             $directives,
-            static function ($hasSkip, $directive) {
+            static function (bool $hasSkip, Directive $directive) : bool {
                 return $hasSkip || $directive->name === 'skip';
-            }
+            },
+            false
         );
         if (! $skip) {
             $directives[] = Directive::skipDirective();
@@ -164,9 +170,10 @@ class BuildSchema
 
         $include = array_reduce(
             $directives,
-            static function ($hasInclude, $directive) {
+            static function (bool $hasInclude, Directive $directive) : bool {
                 return $hasInclude || $directive->name === 'include';
-            }
+            },
+            false
         );
         if (! $include) {
             $directives[] = Directive::includeDirective();
@@ -174,9 +181,10 @@ class BuildSchema
 
         $deprecated = array_reduce(
             $directives,
-            static function ($hasDeprecated, $directive) {
+            static function (bool $hasDeprecated, Directive $directive) : bool {
                 return $hasDeprecated || $directive->name === 'deprecated';
-            }
+            },
+            false
         );
         if (! $deprecated) {
             $directives[] = Directive::deprecatedDirective();

src/Utils/MixedStore.php

@@ -21,9 +21,7 @@ use function is_string;
  * Similar to PHP array, but allows any type of data to act as key (including arrays, objects, scalars)
  *
  * Note: unfortunately when storing array as key - access and modification is O(N)
- * (yet this should be really rare case and should be avoided when possible)
+ * (yet this should rarely be the case and should be avoided when possible)
- *
- * Class MixedStore
  */
 class MixedStore implements ArrayAccess
 {

src/Utils/SchemaExtender.php

@@ -7,13 +7,16 @@ namespace GraphQL\Utils;
 use GraphQL\Error\Error;
 use GraphQL\Language\AST\DirectiveDefinitionNode;
 use GraphQL\Language\AST\DocumentNode;
+use GraphQL\Language\AST\EnumTypeExtensionNode;
+use GraphQL\Language\AST\InputObjectTypeExtensionNode;
+use GraphQL\Language\AST\InterfaceTypeExtensionNode;
 use GraphQL\Language\AST\Node;
-use GraphQL\Language\AST\NodeKind;
 use GraphQL\Language\AST\ObjectTypeExtensionNode;
 use GraphQL\Language\AST\SchemaDefinitionNode;
 use GraphQL\Language\AST\SchemaTypeExtensionNode;
 use GraphQL\Language\AST\TypeDefinitionNode;
 use GraphQL\Language\AST\TypeExtensionNode;
+use GraphQL\Language\AST\UnionTypeExtensionNode;
 use GraphQL\Type\Definition\CustomScalarType;
 use GraphQL\Type\Definition\Directive;
 use GraphQL\Type\Definition\EnumType;
@@ -66,6 +69,7 @@ class SchemaExtender
 
             return $type->extensionASTNodes;
         }
+
         return static::$typeExtensionsMap[$name] ?? null;
     }
 
@@ -74,8 +78,8 @@ class SchemaExtender
      */
     protected static function checkExtensionNode(Type $type, Node $node) : void
     {
-        switch ($node->kind) {
+        switch (true) {
-            case NodeKind::OBJECT_TYPE_EXTENSION:
+            case $node instanceof ObjectTypeExtensionNode:
                 if (! ($type instanceof ObjectType)) {
                     throw new Error(
                         'Cannot extend non-object type "' . $type->name . '".',
@@ -83,7 +87,7 @@ class SchemaExtender
                     );
                 }
                 break;
-            case NodeKind::INTERFACE_TYPE_EXTENSION:
+            case $node instanceof InterfaceTypeExtensionNode:
                 if (! ($type instanceof InterfaceType)) {
                     throw new Error(
                         'Cannot extend non-interface type "' . $type->name . '".',
@@ -91,7 +95,7 @@ class SchemaExtender
                     );
                 }
                 break;
-            case NodeKind::ENUM_TYPE_EXTENSION:
+            case $node instanceof EnumTypeExtensionNode:
                 if (! ($type instanceof EnumType)) {
                     throw new Error(
                         'Cannot extend non-enum type "' . $type->name . '".',
@@ -99,7 +103,7 @@ class SchemaExtender
                     );
                 }
                 break;
-            case NodeKind::UNION_TYPE_EXTENSION:
+            case $node instanceof UnionTypeExtensionNode:
                 if (! ($type instanceof UnionType)) {
                     throw new Error(
                         'Cannot extend non-union type "' . $type->name . '".',
@@ -107,7 +111,7 @@ class SchemaExtender
                     );
                 }
                 break;
-            case NodeKind::INPUT_OBJECT_TYPE_EXTENSION:
+            case $node instanceof InputObjectTypeExtensionNode:
                 if (! ($type instanceof InputObjectType)) {
                     throw new Error(
                         'Cannot extend non-input object type "' . $type->name . '".',
@@ -284,6 +288,7 @@ class SchemaExtender
                 }
             }
         }
+
         return $interfaces;
     }
 
@@ -513,7 +518,14 @@ class SchemaExtender
                 $schemaExtensions[] = $def;
             } elseif ($def instanceof TypeDefinitionNode) {
                 $typeName = isset($def->name) ? $def->name->value : null;
-                if ($schema->getType($typeName)) {
+
+                try {
+                    $type = $schema->getType($typeName);
+                } catch (Error $error) {
+                    $type = null;
+                }
+
+                if ($type) {
                     throw new Error('Type "' . $typeName . '" already exists in the schema. It cannot also be defined in this type definition.', [$def]);
                 }
                 $typeDefinitionMap[$typeName] = $def;
@@ -597,7 +609,9 @@ class SchemaExtender
         }
 
         $schemaExtensionASTNodes = count($schemaExtensions) > 0
-            ? ($schema->extensionASTNodes ? array_merge($schema->extensionASTNodes, $schemaExtensions) : $schemaExtensions)
+            ? ($schema->extensionASTNodes
+                ? array_merge($schema->extensionASTNodes, $schemaExtensions)
+                : $schemaExtensions)
             : $schema->extensionASTNodes;
 
         $types = array_merge(

src/Utils/SchemaPrinter.php

@@ -153,11 +153,8 @@ class SchemaPrinter
         }
 
         $subscriptionType = $schema->getSubscriptionType();
-        if ($subscriptionType && $subscriptionType->name !== 'Subscription') {
-            return false;
-        }
 
-        return true;
+        return ! $subscriptionType || $subscriptionType->name === 'Subscription';
     }
 
     private static function printDirective($directive, $options) : string
@@ -356,8 +353,8 @@ class SchemaPrinter
     private static function printObject(ObjectType $type, array $options) : string
     {
         $interfaces            = $type->getInterfaces();
-        $implementedInterfaces = ! empty($interfaces) ?
+        $implementedInterfaces = ! empty($interfaces)
-            ' implements ' . implode(
+            ? ' implements ' . implode(
                 ' & ',
                 array_map(
                     static function ($i) {
@@ -365,7 +362,8 @@ class SchemaPrinter
                     },
                     $interfaces
                 )
-            ) : '';
+            )
+            : '';
 
         return self::printDescription($options, $type) .
             sprintf("type %s%s {\n%s\n}", $type->name, $implementedInterfaces, self::printFields($options, $type));

src/Utils/TypeComparators.php

@@ -86,18 +86,12 @@ class TypeComparators
 
         // If superType type is an abstract type, maybeSubType type may be a currently
         // possible object type.
-        if (Type::isAbstractType($superType) &&
+        return Type::isAbstractType($superType) &&
             $maybeSubType instanceof ObjectType &&
             $schema->isPossibleType(
                 $superType,
                 $maybeSubType
-            )
+            );
-        ) {
-            return true;
-        }
-
-        // Otherwise, the child type is not a valid subtype of the parent type.
-        return false;
     }
 
     /**
@@ -131,13 +125,11 @@ class TypeComparators
                 return false;
             }
 
-            /** @var $typeB ObjectType */
             // Determine if the latter type is a possible concrete type of the former.
             return $schema->isPossibleType($typeA, $typeB);
         }
 
         if ($typeB instanceof AbstractType) {
-            /** @var $typeA ObjectType */
             // Determine if the former type is a possible concrete type of the latter.
             return $schema->isPossibleType($typeB, $typeA);
         }

src/Utils/TypeInfo.php

@@ -6,12 +6,21 @@ namespace GraphQL\Utils;
 
 use GraphQL\Error\InvariantViolation;
 use GraphQL\Error\Warning;
+use GraphQL\Language\AST\ArgumentNode;
+use GraphQL\Language\AST\DirectiveNode;
+use GraphQL\Language\AST\EnumValueNode;
 use GraphQL\Language\AST\FieldNode;
+use GraphQL\Language\AST\FragmentDefinitionNode;
+use GraphQL\Language\AST\InlineFragmentNode;
 use GraphQL\Language\AST\ListTypeNode;
+use GraphQL\Language\AST\ListValueNode;
 use GraphQL\Language\AST\NamedTypeNode;
 use GraphQL\Language\AST\Node;
-use GraphQL\Language\AST\NodeKind;
 use GraphQL\Language\AST\NonNullTypeNode;
+use GraphQL\Language\AST\ObjectFieldNode;
+use GraphQL\Language\AST\OperationDefinitionNode;
+use GraphQL\Language\AST\SelectionSetNode;
+use GraphQL\Language\AST\VariableDefinitionNode;
 use GraphQL\Type\Definition\CompositeType;
 use GraphQL\Type\Definition\Directive;
 use GraphQL\Type\Definition\EnumType;
@@ -28,6 +37,7 @@ use GraphQL\Type\Definition\UnionType;
 use GraphQL\Type\Definition\WrappingType;
 use GraphQL\Type\Introspection;
 use GraphQL\Type\Schema;
+use SplStack;
 use function array_map;
 use function array_merge;
 use function array_pop;
@@ -35,24 +45,21 @@ use function count;
 use function is_array;
 use function sprintf;
 
-/**
- * Class TypeInfo
- */
 class TypeInfo
 {
     /** @var Schema */
     private $schema;
 
-    /** @var \SplStack<OutputType> */
+    /** @var SplStack<OutputType> */
     private $typeStack;
 
-    /** @var \SplStack<CompositeType> */
+    /** @var SplStack<CompositeType> */
     private $parentTypeStack;
 
-    /** @var \SplStack<InputType> */
+    /** @var SplStack<InputType> */
     private $inputTypeStack;
 
-    /** @var \SplStack<FieldDefinition> */
+    /** @var SplStack<FieldDefinition> */
     private $fieldDefStack;
 
     /** @var Directive */
@@ -155,6 +162,7 @@ class TypeInfo
             if (! $alreadyInMap) {
                 $typeMap[$i] = $type;
             }
+
             return $typeMap;
         }
 
@@ -178,7 +186,7 @@ class TypeInfo
             $nestedTypes = array_merge($nestedTypes, $type->getInterfaces());
         }
         if ($type instanceof ObjectType || $type instanceof InterfaceType) {
-            foreach ((array) $type->getFields() as $fieldName => $field) {
+            foreach ($type->getFields() as $fieldName => $field) {
                 if (! empty($field->args)) {
                     $fieldArgTypes = array_map(
                         static function (FieldArgument $arg) {
@@ -193,12 +201,12 @@ class TypeInfo
             }
         }
         if ($type instanceof InputObjectType) {
-            foreach ((array) $type->getFields() as $fieldName => $field) {
+            foreach ($type->getFields() as $fieldName => $field) {
                 $nestedTypes[] = $field->getType();
             }
         }
-        foreach ($nestedTypes as $type) {
+        foreach ($nestedTypes as $nestedType) {
-            $typeMap = self::extractTypes($type, $typeMap);
+            $typeMap = self::extractTypes($nestedType, $typeMap);
         }
 
         return $typeMap;
@@ -255,13 +263,13 @@ class TypeInfo
         // any assumptions of a valid schema to ensure runtime types are properly
         // checked before continuing since TypeInfo is used as part of validation
         // which occurs before guarantees of schema and document validity.
-        switch ($node->kind) {
+        switch (true) {
-            case NodeKind::SELECTION_SET:
+            case $node instanceof SelectionSetNode:
                 $namedType               = Type::getNamedType($this->getType());
                 $this->parentTypeStack[] = Type::isCompositeType($namedType) ? $namedType : null;
                 break;
 
-            case NodeKind::FIELD:
+            case $node instanceof FieldNode:
                 $parentType = $this->getParentType();
                 $fieldDef   = null;
                 if ($parentType) {
@@ -275,11 +283,11 @@ class TypeInfo
                 $this->typeStack[]     = Type::isOutputType($fieldType) ? $fieldType : null;
                 break;
 
-            case NodeKind::DIRECTIVE:
+            case $node instanceof DirectiveNode:
                 $this->directive = $schema->getDirective($node->name->value);
                 break;
 
-            case NodeKind::OPERATION_DEFINITION:
+            case $node instanceof OperationDefinitionNode:
                 $type = null;
                 if ($node->operation === 'query') {
                     $type = $schema->getQueryType();
@@ -291,22 +299,24 @@ class TypeInfo
                 $this->typeStack[] = Type::isOutputType($type) ? $type : null;
                 break;
 
-            case NodeKind::INLINE_FRAGMENT:
+            case $node instanceof InlineFragmentNode:
-            case NodeKind::FRAGMENT_DEFINITION:
+            case $node instanceof FragmentDefinitionNode:
                 $typeConditionNode = $node->typeCondition;
-                $outputType        = $typeConditionNode ? self::typeFromAST(
+                $outputType        = $typeConditionNode
-                    $schema,
+                    ? self::typeFromAST(
-                    $typeConditionNode
+                        $schema,
-                ) : Type::getNamedType($this->getType());
+                        $typeConditionNode
+                    )
+                    : Type::getNamedType($this->getType());
                 $this->typeStack[] = Type::isOutputType($outputType) ? $outputType : null;
                 break;
 
-            case NodeKind::VARIABLE_DEFINITION:
+            case $node instanceof VariableDefinitionNode:
                 $inputType              = self::typeFromAST($schema, $node->type);
                 $this->inputTypeStack[] = Type::isInputType($inputType) ? $inputType : null; // push
                 break;
 
-            case NodeKind::ARGUMENT:
+            case $node instanceof ArgumentNode:
                 $fieldOrDirective = $this->getDirective() ?: $this->getFieldDef();
                 $argDef           = $argType = null;
                 if ($fieldOrDirective) {
@@ -324,7 +334,7 @@ class TypeInfo
                 $this->inputTypeStack[] = Type::isInputType($argType) ? $argType : null;
                 break;
 
-            case NodeKind::LST:
+            case $node instanceof ListValueNode:
                 $listType               = Type::getNullableType($this->getInputType());
                 $itemType               = $listType instanceof ListOfType
                     ? $listType->getWrappedType()
@@ -332,7 +342,7 @@ class TypeInfo
                 $this->inputTypeStack[] = Type::isInputType($itemType) ? $itemType : null;
                 break;
 
-            case NodeKind::OBJECT_FIELD:
+            case $node instanceof ObjectFieldNode:
                 $objectType     = Type::getNamedType($this->getInputType());
                 $fieldType      = null;
                 $inputFieldType = null;
@@ -344,7 +354,7 @@ class TypeInfo
                 $this->inputTypeStack[] = Type::isInputType($inputFieldType) ? $inputFieldType : null;
                 break;
 
-            case NodeKind::ENUM:
+            case $node instanceof EnumValueNode:
                 $enumType  = Type::getNamedType($this->getInputType());
                 $enumValue = null;
                 if ($enumType instanceof EnumType) {
@@ -458,37 +468,37 @@ class TypeInfo
 
     public function leave(Node $node)
     {
-        switch ($node->kind) {
+        switch (true) {
-            case NodeKind::SELECTION_SET:
+            case $node instanceof SelectionSetNode:
                 array_pop($this->parentTypeStack);
                 break;
 
-            case NodeKind::FIELD:
+            case $node instanceof FieldNode:
                 array_pop($this->fieldDefStack);
                 array_pop($this->typeStack);
                 break;
 
-            case NodeKind::DIRECTIVE:
+            case $node instanceof DirectiveNode:
                 $this->directive = null;
                 break;
 
-            case NodeKind::OPERATION_DEFINITION:
+            case $node instanceof OperationDefinitionNode:
-            case NodeKind::INLINE_FRAGMENT:
+            case $node instanceof InlineFragmentNode:
-            case NodeKind::FRAGMENT_DEFINITION:
+            case $node instanceof FragmentDefinitionNode:
                 array_pop($this->typeStack);
                 break;
-            case NodeKind::VARIABLE_DEFINITION:
+            case $node instanceof VariableDefinitionNode:
                 array_pop($this->inputTypeStack);
                 break;
-            case NodeKind::ARGUMENT:
+            case $node instanceof ArgumentNode:
                 $this->argument = null;
                 array_pop($this->inputTypeStack);
                 break;
-            case NodeKind::LST:
+            case $node instanceof ListValueNode:
-            case NodeKind::OBJECT_FIELD:
+            case $node instanceof ObjectFieldNode:
                 array_pop($this->inputTypeStack);
                 break;
-            case NodeKind::ENUM:
+            case $node instanceof EnumValueNode:
                 $this->enumValue = null;
                 break;
         }

src/Utils/Utils.php

@@ -264,8 +264,8 @@ class Utils
         $grouped = [];
         foreach ($traversable as $key => $value) {
             $newKeys = (array) $keyFn($value, $key);
-            foreach ($newKeys as $key) {
+            foreach ($newKeys as $newKey) {
-                $grouped[$key][] = $value;
+                $grouped[$newKey][] = $value;
             }
         }
 

src/Utils/Value.php

@@ -199,7 +199,7 @@ class Value
                 }
 
                 $suggestions = Utils::suggestionList(
-                    $fieldName,
+                    (string) $fieldName,
                     array_keys($fields)
                 );
                 $didYouMean  = $suggestions

src/Validator/Rules/DisableIntrospection.php

@@ -52,6 +52,6 @@ class DisableIntrospection extends QuerySecurityRule
 
     protected function isEnabled()
     {
-        return $this->isEnabled !== static::DISABLED;
+        return $this->isEnabled !== self::DISABLED;
     }
 }

src/Validator/Rules/KnownArgumentNames.php

@@ -6,6 +6,8 @@ namespace GraphQL\Validator\Rules;
 
 use GraphQL\Error\Error;
 use GraphQL\Language\AST\ArgumentNode;
+use GraphQL\Language\AST\DirectiveNode;
+use GraphQL\Language\AST\FieldNode;
 use GraphQL\Language\AST\Node;
 use GraphQL\Language\AST\NodeKind;
 use GraphQL\Language\AST\NodeList;
@@ -34,7 +36,7 @@ class KnownArgumentNames extends ValidationRule
                 }
 
                 $argumentOf = $ancestors[count($ancestors) - 1];
-                if ($argumentOf->kind === NodeKind::FIELD) {
+                if ($argumentOf instanceof FieldNode) {
                     $fieldDef   = $context->getFieldDef();
                     $parentType = $context->getParentType();
                     if ($fieldDef && $parentType) {
@@ -56,7 +58,7 @@ class KnownArgumentNames extends ValidationRule
                             [$node]
                         ));
                     }
-                } elseif ($argumentOf->kind === NodeKind::DIRECTIVE) {
+                } elseif ($argumentOf instanceof DirectiveNode) {
                     $directive = $context->getDirective();
                     if ($directive) {
                         $context->reportError(new Error(

src/Validator/Rules/KnownDirectives.php

@@ -7,10 +7,31 @@ namespace GraphQL\Validator\Rules;
 use GraphQL\Error\Error;
 use GraphQL\Language\AST\DirectiveDefinitionNode;
 use GraphQL\Language\AST\DirectiveNode;
+use GraphQL\Language\AST\EnumTypeDefinitionNode;
+use GraphQL\Language\AST\EnumTypeExtensionNode;
+use GraphQL\Language\AST\EnumValueDefinitionNode;
+use GraphQL\Language\AST\FieldDefinitionNode;
+use GraphQL\Language\AST\FieldNode;
+use GraphQL\Language\AST\FragmentDefinitionNode;
+use GraphQL\Language\AST\FragmentSpreadNode;
+use GraphQL\Language\AST\InlineFragmentNode;
 use GraphQL\Language\AST\InputObjectTypeDefinitionNode;
+use GraphQL\Language\AST\InputObjectTypeExtensionNode;
+use GraphQL\Language\AST\InputValueDefinitionNode;
+use GraphQL\Language\AST\InterfaceTypeDefinitionNode;
+use GraphQL\Language\AST\InterfaceTypeExtensionNode;
 use GraphQL\Language\AST\Node;
 use GraphQL\Language\AST\NodeKind;
 use GraphQL\Language\AST\NodeList;
+use GraphQL\Language\AST\ObjectTypeDefinitionNode;
+use GraphQL\Language\AST\ObjectTypeExtensionNode;
+use GraphQL\Language\AST\OperationDefinitionNode;
+use GraphQL\Language\AST\ScalarTypeDefinitionNode;
+use GraphQL\Language\AST\ScalarTypeExtensionNode;
+use GraphQL\Language\AST\SchemaDefinitionNode;
+use GraphQL\Language\AST\SchemaTypeExtensionNode;
+use GraphQL\Language\AST\UnionTypeDefinitionNode;
+use GraphQL\Language\AST\UnionTypeExtensionNode;
 use GraphQL\Language\DirectiveLocation;
 use GraphQL\Validator\ValidationContext;
 use function array_map;
@@ -96,8 +117,8 @@ class KnownDirectives extends ValidationRule
     private function getDirectiveLocationForASTPath(array $ancestors)
     {
         $appliedTo = $ancestors[count($ancestors) - 1];
-        switch ($appliedTo->kind) {
+        switch (true) {
-            case NodeKind::OPERATION_DEFINITION:
+            case $appliedTo instanceof OperationDefinitionNode:
                 switch ($appliedTo->operation) {
                     case 'query':
                         return DirectiveLocation::QUERY;
@@ -107,40 +128,40 @@ class KnownDirectives extends ValidationRule
                         return DirectiveLocation::SUBSCRIPTION;
                 }
                 break;
-            case NodeKind::FIELD:
+            case $appliedTo instanceof FieldNode:
                 return DirectiveLocation::FIELD;
-            case NodeKind::FRAGMENT_SPREAD:
+            case $appliedTo instanceof FragmentSpreadNode:
                 return DirectiveLocation::FRAGMENT_SPREAD;
-            case NodeKind::INLINE_FRAGMENT:
+            case $appliedTo instanceof InlineFragmentNode:
                 return DirectiveLocation::INLINE_FRAGMENT;
-            case NodeKind::FRAGMENT_DEFINITION:
+            case $appliedTo instanceof FragmentDefinitionNode:
                 return DirectiveLocation::FRAGMENT_DEFINITION;
-            case NodeKind::SCHEMA_DEFINITION:
+            case $appliedTo instanceof SchemaDefinitionNode:
-            case NodeKind::SCHEMA_EXTENSION:
+            case $appliedTo instanceof SchemaTypeExtensionNode:
                 return DirectiveLocation::SCHEMA;
-            case NodeKind::SCALAR_TYPE_DEFINITION:
+            case $appliedTo instanceof ScalarTypeDefinitionNode:
-            case NodeKind::SCALAR_TYPE_EXTENSION:
+            case $appliedTo instanceof ScalarTypeExtensionNode:
                 return DirectiveLocation::SCALAR;
-            case NodeKind::OBJECT_TYPE_DEFINITION:
+            case $appliedTo instanceof ObjectTypeDefinitionNode:
-            case NodeKind::OBJECT_TYPE_EXTENSION:
+            case $appliedTo instanceof ObjectTypeExtensionNode:
                 return DirectiveLocation::OBJECT;
-            case NodeKind::FIELD_DEFINITION:
+            case $appliedTo instanceof FieldDefinitionNode:
                 return DirectiveLocation::FIELD_DEFINITION;
-            case NodeKind::INTERFACE_TYPE_DEFINITION:
+            case $appliedTo instanceof InterfaceTypeDefinitionNode:
-            case NodeKind::INTERFACE_TYPE_EXTENSION:
+            case $appliedTo instanceof InterfaceTypeExtensionNode:
                 return DirectiveLocation::IFACE;
-            case NodeKind::UNION_TYPE_DEFINITION:
+            case $appliedTo instanceof UnionTypeDefinitionNode:
-            case NodeKind::UNION_TYPE_EXTENSION:
+            case $appliedTo instanceof UnionTypeExtensionNode:
                 return DirectiveLocation::UNION;
-            case NodeKind::ENUM_TYPE_DEFINITION:
+            case $appliedTo instanceof EnumTypeDefinitionNode:
-            case NodeKind::ENUM_TYPE_EXTENSION:
+            case $appliedTo instanceof EnumTypeExtensionNode:
                 return DirectiveLocation::ENUM;
-            case NodeKind::ENUM_VALUE_DEFINITION:
+            case $appliedTo instanceof EnumValueDefinitionNode:
                 return DirectiveLocation::ENUM_VALUE;
-            case NodeKind::INPUT_OBJECT_TYPE_DEFINITION:
+            case $appliedTo instanceof InputObjectTypeDefinitionNode:
-            case NodeKind::INPUT_OBJECT_TYPE_EXTENSION:
+            case $appliedTo instanceof InputObjectTypeExtensionNode:
                 return DirectiveLocation::INPUT_OBJECT;
-            case NodeKind::INPUT_VALUE_DEFINITION:
+            case $appliedTo instanceof InputValueDefinitionNode:
                 $parentNode = $ancestors[count($ancestors) - 3];
 
                 return $parentNode instanceof InputObjectTypeDefinitionNode

src/Validator/Rules/LoneAnonymousOperation.php

@@ -30,7 +30,7 @@ class LoneAnonymousOperation extends ValidationRule
                 $tmp = Utils::filter(
                     $node->definitions,
                     static function (Node $definition) {
-                        return $definition->kind === NodeKind::OPERATION_DEFINITION;
+                        return $definition instanceof OperationDefinitionNode;
                     }
                 );