GQL: Enable fetching statement string values

Bug: T400148
Change-Id: Ib6964ed9d7efce98a30195a5a8ab20247724470e

Author: jakobw

repo/includes/GraphQLPrototype/Schema.php

@@ -90,6 +90,12 @@ private function statementType(): ObjectType {
 						],
 					],
 				] ),
+				'value' => new ObjectType( [
+					'name' => 'StatementValue',
+					'fields' => [
+						'content' => Type::nonNull( Type::string() ),
+					],
+				] ),
 			],
 		] );
 	}

repo/includes/GraphQLPrototype/StatementsResolver.php

@@ -2,9 +2,11 @@
 
 namespace Wikibase\Repo\GraphQLPrototype;
 
+use DataValues\StringValue;
 use Wikibase\DataModel\Entity\Item;
 use Wikibase\DataModel\Entity\ItemId;
 use Wikibase\DataModel\Services\Lookup\EntityLookup;
+use Wikibase\DataModel\Snak\PropertyValueSnak;
 use Wikibase\DataModel\Statement\Statement;
 
 /**
@@ -23,8 +25,15 @@ public function fetchStatements( array $rootValue ): array {
 		return array_map(
 			fn( Statement $statement ) => [
 				'property' => [ 'id' => $statement->getPropertyId()->getSerialization() ],
+				// @phan-suppress-next-line PhanUndeclaredMethod guaranteed to be a string value per array_filter
+				'value' => [ 'content' => $statement->getMainSnak()->getDataValue()->getValue() ],
 			],
-			iterator_to_array( $item->getStatements() )
+			array_filter(
+				iterator_to_array( $item->getStatements() ),
+				fn( Statement $statement ) => $statement->getMainSnak() instanceof PropertyValueSnak
+					// @phan-suppress-next-line PhanUndeclaredMethod guaranteed to be a value snak per line above
+					&& $statement->getMainSnak()->getDataValue() instanceof StringValue
+			)
 		);
 	}
 }

repo/tests/phpunit/includes/GraphQLPrototype/GraphQLQueryServiceTest.php

@@ -49,10 +49,22 @@ public function addDBDataOnce() {
 		$this->saveEntity( $stringProperty );
 		self::$stringProperty = $stringProperty;
 
+		$timeProperty = new Property(
+			null,
+			new Fingerprint( new TermList( [ new Term( 'en', 'date of birth' ) ] ) ),
+			'time',
+		);
+		$this->saveEntity( $timeProperty );
+
 		$item = NewItem::withLabel( 'en', 'potato' )
 			->andLabel( 'de', 'Kartoffel' )
 			->andStatement(
-				NewStatement::noValueFor( self::$stringProperty->getId() )->build()
+				NewStatement::forProperty( $stringProperty->getId() )
+					->withValue( 'potato value' )
+					->build()
+			)
+			->andStatement( // this statement will get filtered out, because we don't support time values yet
+				NewStatement::noValueFor( $timeProperty->getId() )->build()
 			)
 			->build();
 		$this->saveEntity( $item );
@@ -139,6 +151,36 @@ public function testItemNotFound(): void {
 		);
 	}
 
+	public function testStatementsQueryWithStringValue(): void {
+		$itemId = self::$item->getId()->getSerialization();
+		$value = self::$item->getStatements()
+			->getByPropertyId( self::$stringProperty->getId() )->toArray()[0]
+			->getMainSnak()->getDataValue()->getValue();
+
+		$this->assertNotNull( $value );
+		$this->assertEquals(
+			[ 'data' => [ 'item' => [
+				'statements' => [
+					[
+						'property' => [
+							'id' => self::$stringProperty->getId()->getSerialization(),
+						],
+						'value' => [ 'content' => $value ],
+					],
+				],
+			] ] ],
+			$this->newGraphQLService()->query( "
+			query {
+				item(id: \"$itemId\") {
+					statements {
+						property { id }
+						value { content }
+					}
+				}
+			}" )
+		);
+	}
+
 	public function newGraphQLService(): GraphQLQueryService {
 		$entityLookup = WikibaseRepo::getEntityLookup();