GraphQL\Utils\TypeInfo::getFieldDefinition PHP Method

    private static function getFieldDefinition(Schema $schema, Type $parentType, FieldNode $fieldNode)
    {
        $name = $fieldNode->name->value;
        $schemaMeta = Introspection::schemaMetaFieldDef();
        if ($name === $schemaMeta->name && $schema->getQueryType() === $parentType) {
            return $schemaMeta;
        }
        $typeMeta = Introspection::typeMetaFieldDef();
        if ($name === $typeMeta->name && $schema->getQueryType() === $parentType) {
            return $typeMeta;
        }
        $typeNameMeta = Introspection::typeNameMetaFieldDef();
        if ($name === $typeNameMeta->name && $parentType instanceof CompositeType) {
            return $typeNameMeta;
        }
        if ($parentType instanceof ObjectType || $parentType instanceof InterfaceType) {
            $fields = $parentType->getFields();
            return isset($fields[$name]) ? $fields[$name] : null;
        }
        return null;
    }