Implement BuildClientSchema (#539)

* wip

* wip

* Finish implementation

* Add Introspection::fromSchema

* wip test

* format

* types

* Use array instead of stdClass

* Add tests

* Mention TypeKind constants change in UPGRADE.md

* Adress review comments

* Some codestyle fixes

* Fix codestyle and static analysis

* Build some tests

* Add more tests

* Fix test and implementation

* Fix codestyle

* Change wording

* Revert implementation of defaultValueExists

* Fix codestyle

* Call instance method not statically

* Fix codestyle

* Make callable functions public

* Update src/Type/Introspection.php

Co-Authored-By: Šimon Podlipský <simon@podlipsky.net>

* Update tests/Utils/BuildClientSchemaTest.php

Co-Authored-By: Šimon Podlipský <simon@podlipsky.net>

* Iterable

* Revert change in Utils.php

* Re-add minimal docs fix

Co-authored-by: Šimon Podlipský <simon@podlipsky.net>

Author: spawnia

UPGRADE.md

@@ -3,6 +3,10 @@
 ### Breaking (major): dropped deprecations
  - dropped deprecated `GraphQL\Schema`. Use `GraphQL\Type\Schema`.
 
+### Breaking: change TypeKind constants
+The constants in `\GraphQL\Type\TypeKind` were partly renamed and their values
+have been changed to match their name instead of a numeric index.
+ 
 ## Upgrade v0.12.x > v0.13.x
 
 ### Breaking (major): minimum supported version of PHP

src/Type/Introspection.php

@@ -5,6 +5,7 @@
 namespace GraphQL\Type;
 
 use Exception;
+use GraphQL\GraphQL;
 use GraphQL\Language\DirectiveLocation;
 use GraphQL\Language\Printer;
 use GraphQL\Type\Definition\Directive;
@@ -184,6 +185,34 @@ public static function getTypes()
         ];
     }
 
+    /**
+     * Build an introspection query from a Schema
+     *
+     * Introspection is useful for utilities that care about type and field
+     * relationships, but do not need to traverse through those relationships.
+     *
+     * This is the inverse of BuildClientSchema::build(). The primary use case is outside
+     * of the server context, for instance when doing schema comparisons.
+     *
+     * Options:
+     *   - descriptions
+     *     Whether to include descriptions in the introspection result.
+     *     Default: true
+     *
+     * @param array<string, bool> $options
+     *
+     * @return array<string, array<mixed>>|null
+     */
+    public static function fromSchema(Schema $schema, array $options = []) : ?array
+    {
+        $result = GraphQL::executeQuery(
+            $schema,
+            self::getIntrospectionQuery($options)
+        );
+
+        return $result->data;
+    }
+
     public static function _schema()
     {
         if (! isset(self::$map['__Schema'])) {
@@ -263,7 +292,7 @@ public static function _type()
                             'resolve' => static function (Type $type) {
                                 switch (true) {
                                     case $type instanceof ListOfType:
-                                        return TypeKind::LIST_KIND;
+                                        return TypeKind::LIST;
                                     case $type instanceof NonNull:
                                         return TypeKind::NON_NULL;
                                     case $type instanceof ScalarType:
@@ -275,7 +304,7 @@ public static function _type()
                                     case $type instanceof InputObjectType:
                                         return TypeKind::INPUT_OBJECT;
                                     case $type instanceof InterfaceType:
-                                        return TypeKind::INTERFACE_KIND;
+                                        return TypeKind::INTERFACE;
                                     case $type instanceof UnionType:
                                         return TypeKind::UNION;
                                     default:
@@ -408,7 +437,7 @@ public static function _typeKind()
                         'description' => 'Indicates this type is an object. `fields` and `interfaces` are valid fields.',
                     ],
                     'INTERFACE'    => [
-                        'value'       => TypeKind::INTERFACE_KIND,
+                        'value'       => TypeKind::INTERFACE,
                         'description' => 'Indicates this type is an interface. `fields` and `possibleTypes` are valid fields.',
                     ],
                     'UNION'        => [
@@ -424,7 +453,7 @@ public static function _typeKind()
                         'description' => 'Indicates this type is an input object. `inputFields` is a valid field.',
                     ],
                     'LIST'         => [
-                        'value'       => TypeKind::LIST_KIND,
+                        'value'       => TypeKind::LIST,
                         'description' => 'Indicates this type is a list. `ofType` is a valid field.',
                     ],
                     'NON_NULL'     => [

src/Type/Schema.php

@@ -238,7 +238,7 @@ private function collectAllTypes()
      */
     public function getDirectives()
     {
-        return $this->config->directives ?: GraphQL::getStandardDirectives();
+        return $this->config->directives ?? GraphQL::getStandardDirectives();
     }
 
     /**

src/Type/TypeKind.php

@@ -6,12 +6,12 @@
 
 class TypeKind
 {
-    const SCALAR         = 0;
-    const OBJECT         = 1;
-    const INTERFACE_KIND = 2;
-    const UNION          = 3;
-    const ENUM           = 4;
-    const INPUT_OBJECT   = 5;
-    const LIST_KIND      = 6;
-    const NON_NULL       = 7;
+    const SCALAR       = 'SCALAR';
+    const OBJECT       = 'OBJECT';
+    const INTERFACE    = 'INTERFACE';
+    const UNION        = 'UNION';
+    const ENUM         = 'ENUM';
+    const INPUT_OBJECT = 'INPUT_OBJECT';
+    const LIST         = 'LIST';
+    const NON_NULL     = 'NON_NULL';
 }