MC-36456: union implementation

app/code/Magento/GraphQl/etc/di.xml

@@ -29,6 +29,7 @@
         <arguments>
             <argument name="factoryMapByConfigElementType" xsi:type="array">
                 <item name="graphql_interface" xsi:type="object">Magento\Framework\GraphQl\Config\Element\InterfaceFactory</item>
+                <item name="graphql_union" xsi:type="object">Magento\Framework\GraphQl\Config\Element\UnionFactory</item>
                 <item name="graphql_type" xsi:type="object">Magento\Framework\GraphQl\Config\Element\TypeFactory</item>
                 <item name="graphql_input" xsi:type="object">Magento\Framework\GraphQl\Config\Element\InputFactory</item>
                 <item name="graphql_enum" xsi:type="object">Magento\Framework\GraphQl\Config\Element\EnumFactory</item>
@@ -64,6 +65,7 @@
                 <item name="Magento\Framework\GraphQl\Config\Element\Type" xsi:type="string">Magento\Framework\GraphQl\Schema\Type\Output\OutputTypeObject</item>
                 <item name="Magento\Framework\GraphQl\Config\Element\Input" xsi:type="string">Magento\Framework\GraphQl\Schema\Type\Input\InputObjectType</item>
                 <item name="Magento\Framework\GraphQl\Config\Element\InterfaceType" xsi:type="string">Magento\Framework\GraphQl\Schema\Type\Output\OutputInterfaceObject</item>
+                <item name="Magento\Framework\GraphQl\Config\Element\UnionType" xsi:type="string">Magento\Framework\GraphQl\Schema\Type\Output\OutputUnionObject</item>
                 <item name="Magento\Framework\GraphQl\Config\Element\Enum" xsi:type="string">Magento\Framework\GraphQl\Schema\Type\Enum\Enum</item>
             </argument>
         </arguments>
@@ -78,13 +80,15 @@
             <argument name="formatters" xsi:type="array">
                 <item name="fields" xsi:type="object">Magento\Framework\GraphQl\Schema\Type\Output\ElementMapper\Formatter\Fields</item>
                 <item name="interfaces" xsi:type="object">Magento\Framework\GraphQl\Schema\Type\Output\ElementMapper\Formatter\Interfaces</item>
+                <item name="unions" xsi:type="object">Magento\Framework\GraphQl\Schema\Type\Output\ElementMapper\Formatter\Unions</item>
                 <item name="resolveType" xsi:type="object">Magento\Framework\GraphQl\Schema\Type\Output\ElementMapper\Formatter\ResolveType</item>
             </argument>
         </arguments>
     </type>
     <type name="Magento\Framework\GraphQlSchemaStitching\GraphQlReader\TypeReaderComposite">
         <arguments>
             <argument name="typeReaders" xsi:type="array">
+                <item name="union_type" xsi:type="object">Magento\Framework\GraphQlSchemaStitching\GraphQlReader\Reader\UnionType</item>
                 <item name="enum_type" xsi:type="object">Magento\Framework\GraphQlSchemaStitching\GraphQlReader\Reader\EnumType</item>
                 <item name="object_type" xsi:type="object">Magento\Framework\GraphQlSchemaStitching\GraphQlReader\Reader\ObjectType</item>
                 <item name="input_object_type" xsi:type="object">Magento\Framework\GraphQlSchemaStitching\GraphQlReader\Reader\InputObjectType</item>

app/code/Magento/GraphQl/etc/schema.graphqls

@@ -30,14 +30,14 @@ directive @resolver(class: String="") on QUERY
     | OBJECT
     | FIELD_DEFINITION
     | ARGUMENT_DEFINITION
-    | INTERFACE
-    | UNION
     | ENUM
     | ENUM_VALUE
     | INPUT_OBJECT
     | INPUT_FIELD_DEFINITION
 
-directive @typeResolver(class: String="") on INTERFACE | OBJECT
+directive @typeResolver(class: String="") on UNION
+    | INTERFACE
+    | OBJECT
 
 directive @cache(cacheIdentity: String="" cacheable: Boolean=true) on QUERY
 

dev/tests/api-functional/_files/Magento/TestModuleGraphQlQuery/Model/Resolver/Item.php

@@ -11,6 +11,9 @@
 use Magento\Framework\GraphQl\Config\Element\Field;
 use Magento\Framework\GraphQl\Query\ResolverInterface;
 
+/**
+ * Resolver for Item
+ */
 class Item implements ResolverInterface
 {
     /**

dev/tests/api-functional/_files/Magento/TestModuleGraphQlQuery/Model/Resolver/TestUnion.php

@@ -0,0 +1,34 @@
+<?php
+/**
+ * Copyright © Magento, Inc. All rights reserved.
+ * See COPYING.txt for license details.
+ */
+declare(strict_types=1);
+
+namespace Magento\TestModuleGraphQlQuery\Model\Resolver;
+
+use Magento\Framework\GraphQl\Config\Element\Field;
+use Magento\Framework\GraphQl\Query\ResolverInterface;
+use Magento\Framework\GraphQl\Schema\Type\ResolveInfo;
+
+/**
+ * Resolver for Union type TestUnion
+ */
+class TestUnion implements ResolverInterface
+{
+    /**
+     * @inheritDoc
+     */
+    public function resolve(
+        Field $field,
+        $context,
+        ResolveInfo $info,
+        array $value = null,
+        array $args = null
+    ) {
+        return [
+            'custom_name1' => 'custom_name1_value',
+            'custom_name2' => 'custom_name2_value',
+        ];
+    }
+}

dev/tests/api-functional/_files/Magento/TestModuleGraphQlQuery/Model/Resolver/UnionTypeResolver.php

@@ -0,0 +1,27 @@
+<?php
+/**
+ * Copyright © Magento, Inc. All rights reserved.
+ * See COPYING.txt for license details.
+ */
+declare(strict_types=1);
+
+namespace Magento\TestModuleGraphQlQuery\Model\Resolver;
+
+use Magento\Framework\GraphQl\Query\Resolver\TypeResolverInterface;
+
+/**
+ * Type Resolver for union
+ */
+class UnionTypeResolver implements TypeResolverInterface
+{
+    /**
+     * @inheritDoc
+     */
+    public function resolveType(array $data): string
+    {
+        if (!empty($data)) {
+            return 'TypeCustom1';
+        }
+        return '';
+    }
+}

dev/tests/api-functional/_files/Magento/TestModuleGraphQlQuery/etc/schema.graphqls

@@ -3,6 +3,7 @@
 
 type Query {
     testItem(id: Int!) : Item @resolver(class: "Magento\\TestModuleGraphQlQuery\\Model\\Resolver\\Item")
+    testUnion: TestUnion @resolver(class: "Magento\\TestModuleGraphQlQuery\\Model\\Resolver\\TestUnion")
 }
 
 type Mutation {
@@ -18,3 +19,14 @@ type MutationItem {
     item_id: Int
     name: String
 }
+
+union TestUnion @doc(description: "some kind of union") @typeResolver(class: "Magento\\TestModuleGraphQlQuery\\Model\\Resolver\\UnionTypeResolver")  =
+    TypeCustom1 | TypeCustom2
+
+type TypeCustom1 {
+    custom_name1: String
+}
+
+type TypeCustom2 {
+    custom_name2: String
+}

dev/tests/api-functional/testsuite/Magento/GraphQl/TestModule/GraphQlQueryTest.php

@@ -10,7 +10,7 @@
 use Magento\TestFramework\TestCase\GraphQlAbstract;
 
 /**
- * Class GraphQlQueryTest
+ * Test for basic GraphQl features
  */
 class GraphQlQueryTest extends GraphQlAbstract
 {
@@ -100,4 +100,29 @@ public function testQueryViaGetRequestWithVariablesReturnsResults()
 
         $this->assertArrayHasKey('testItem', $response);
     }
+
+    public function testQueryTestUnionResults()
+    {
+        $query = <<<QUERY
+{
+    testUnion {
+      __typename
+      ... on TypeCustom1 {
+          custom_name1
+      }
+      ... on TypeCustom2 {
+          custom_name2
+      }
+    }
+}
+QUERY;
+
+        $response = $this->graphQlQuery($query);
+
+        $this->assertArrayHasKey('testUnion', $response);
+        $testUnion = $response['testUnion'];
+        $this->assertArrayHasKey('custom_name1', $testUnion);
+        $this->assertEquals('custom_name1_value', $testUnion['custom_name1']);
+        $this->assertArrayNotHasKey('custom_name2', $testUnion);
+    }
 }

lib/internal/Magento/Framework/GraphQl/Config/Element/Type.php

@@ -73,7 +73,15 @@ public function getFields() : array
     /**
      * Get interfaces the type implements, if any. Return an empty array if none are configured.
      *
-     * @return string[]
+     * Example return array(
+     *     array(
+     *         'interface' => 'SomeDefinedTypeInterface',
+     *         'copyFields' => true
+     *     ),
+     *     ...
+     * ),
+     *
+     * @return array
      */
     public function getInterfaces() : array
     {

lib/internal/Magento/Framework/GraphQl/Config/Element/UnionFactory.php

@@ -0,0 +1,69 @@
+<?php
+/**
+ * Copyright © Magento, Inc. All rights reserved.
+ * See COPYING.txt for license details.
+ */
+declare(strict_types=1);
+
+namespace Magento\Framework\GraphQl\Config\Element;
+
+use Magento\Framework\GraphQl\Config\ConfigElementFactoryInterface;
+use Magento\Framework\GraphQl\Config\ConfigElementInterface;
+use Magento\Framework\ObjectManagerInterface;
+
+/**
+ * Factory for config elements of 'union' type.
+ */
+class UnionFactory implements ConfigElementFactoryInterface
+{
+    /**
+     * @var ObjectManagerInterface
+     */
+    private $objectManager;
+
+    /**
+     * @param ObjectManagerInterface $objectManager
+     */
+    public function __construct(
+        ObjectManagerInterface $objectManager
+    ) {
+        $this->objectManager = $objectManager;
+    }
+
+    /**
+     * Instantiate an object representing 'union' GraphQL config element.
+     *
+     * @param array $data
+     * @return ConfigElementInterface
+     */
+    public function createFromConfigData(array $data): ConfigElementInterface
+    {
+        return $this->create($data, $data['types'] ?? []);
+    }
+
+    /**
+     * Create union object based off array of configured GraphQL.
+     *
+     * Union data must contain name, type resolver, and possible concrete types definitions
+     * The type resolver should point to an implementation of the TypeResolverInterface
+     * that decides what concrete GraphQL type to output. Description is the only optional field.
+     *
+     * @param array $unionData
+     * @param array $types
+     * @return UnionType
+     */
+    public function create(
+        array $unionData,
+        array $types
+    ) : UnionType {
+        return $this->objectManager->create(
+            UnionType::class,
+            [
+                'name' => $unionData['name'],
+                'typeResolver' => $unionData['typeResolver'],
+                'types' => $types,
+                'description' => isset($unionData['description']) ? $unionData['description'] : ''
+            ]
+        );
+    }
+}

lib/internal/Magento/Framework/GraphQl/Config/Element/UnionInterface.php

@@ -0,0 +1,23 @@
+<?php
+/**
+ * Copyright © Magento, Inc. All rights reserved.
+ * See COPYING.txt for license details.
+ */
+declare(strict_types=1);
+
+namespace Magento\Framework\GraphQl\Config\Element;
+
+use Magento\Framework\GraphQl\Config\ConfigElementInterface;
+
+/**
+ * Defines the contract for the union configuration data type.
+ */
+interface UnionInterface extends ConfigElementInterface
+{
+    /**
+     * Get a list of fields that make up the possible return or input values of a type.
+     *
+     * @return Type[]
+     */
+    public function getTypes(): array;
+}

lib/internal/Magento/Framework/GraphQl/Config/Element/UnionType.php

@@ -0,0 +1,92 @@
+<?php
+/**
+ * Copyright © Magento, Inc. All rights reserved.
+ * See COPYING.txt for license details.
+ */
+declare(strict_types=1);
+
+namespace Magento\Framework\GraphQl\Config\Element;
+
+/**
+ * Class representing 'union' GraphQL config element.
+ */
+class UnionType implements UnionInterface
+{
+    /**
+     * @var string
+     */
+    private $name;
+
+    /**
+     * @var string[]
+     */
+    private $types;
+
+    /**
+     * @var string
+     */
+    private $typeResolver;
+
+    /**
+     * @var string
+     */
+    private $description;
+
+    /**
+     * @param string $name
+     * @param string $typeResolver
+     * @param string[] $types
+     * @param string $description
+     */
+    public function __construct(
+        string $name,
+        string $typeResolver,
+        array $types,
+        string $description
+    ) {
+        $this->name = $name;
+        $this->types = $types;
+        $this->typeResolver = $typeResolver;
+        $this->description = $description;
+    }
+
+    /**
+     * Get the type name.
+     *
+     * @return string
+     */
+    public function getName(): string
+    {
+        return $this->name;
+    }
+
+    /**
+     * Get a list of fields that make up the possible return or input values of a type.
+     *
+     * @return string[]
+     */
+    public function getTypes(): array
+    {
+        return $this->types;
+    }
+
+    /**
+     * Return the name of the resolver class that determines the concrete type to display in the result.
+     *
+     * @return string
+     */
+    public function getTypeResolver(): string
+    {
+        return $this->typeResolver;
+    }
+
+    /**
+     * Get a human-readable description of the type.
+     *
+     * @return string
+     */
+    public function getDescription(): string
+    {
+        return $this->description;
+    }
+}

lib/internal/Magento/Framework/GraphQl/Query/Resolver/Argument/SearchCriteria/ArgumentApplier/Filter.php

@@ -51,7 +51,7 @@ public function __construct(
     }
 
     /**
-     * {@inheritdoc}
+     * @inheritDoc
      */
     public function applyArgument(
         SearchCriteriaInterface $searchCriteria,