Allow providing default field resolver for execution call

src/Executor/ExecutionContext.php

@@ -44,12 +44,17 @@ class ExecutionContext
      */
     public $variableValues;
 
+    /**
+     * @var callable
+     */
+    public $fieldResolver;
+
     /**
      * @var array
      */
     public $errors;
 
-    public function __construct($schema, $fragments, $root, $contextValue, $operation, $variables, $errors)
+    public function __construct($schema, $fragments, $root, $contextValue, $operation, $variables, $errors, $fieldResolver)
     {
         $this->schema = $schema;
         $this->fragments = $fragments;
@@ -58,6 +63,7 @@ class ExecutionContext
         $this->operation = $operation;
         $this->variableValues = $variables;
         $this->errors = $errors ?: [];
+        $this->fieldResolver = $fieldResolver;
     }
 
     public function addError(Error $error)

src/Executor/Executor.php

@@ -89,9 +89,18 @@ class Executor
      * @param $contextValue
      * @param array|\ArrayAccess $variableValues
      * @param null $operationName
+     * @param callable $fieldResolver
      * @return ExecutionResult|Promise
      */
-    public static function execute(Schema $schema, DocumentNode $ast, $rootValue = null, $contextValue = null, $variableValues = null, $operationName = null)
+    public static function execute(
+        Schema $schema,
+        DocumentNode $ast,
+        $rootValue = null,
+        $contextValue = null,
+        $variableValues = null,
+        $operationName = null,
+        $fieldResolver = null
+    )
     {
         if (null !== $variableValues) {
             Utils::invariant(
@@ -106,7 +115,15 @@ class Executor
             );
         }
 
-        $exeContext = self::buildExecutionContext($schema, $ast, $rootValue, $contextValue, $variableValues, $operationName);
+        $exeContext = self::buildExecutionContext(
+            $schema,
+            $ast,
+            $rootValue,
+            $contextValue,
+            $variableValues,
+            $operationName,
+            $fieldResolver
+        );
         $promiseAdapter = self::getPromiseAdapter();
 
         $executor = new self($exeContext, $promiseAdapter);
@@ -129,6 +146,8 @@ class Executor
      * @param $contextValue
      * @param $rawVariableValues
      * @param string $operationName
+     * @param callable $fieldResolver
+     *
      * @return ExecutionContext
      * @throws Error
      */
@@ -138,7 +157,8 @@ class Executor
         $rootValue,
         $contextValue,
         $rawVariableValues,
-        $operationName = null
+        $operationName = null,
+        $fieldResolver = null
     )
     {
         $errors = [];
@@ -183,7 +203,16 @@ class Executor
             $rawVariableValues ?: []
         );
 
-        $exeContext = new ExecutionContext($schema, $fragments, $rootValue, $contextValue, $operation, $variableValues, $errors);
+        $exeContext = new ExecutionContext(
+            $schema,
+            $fragments,
+            $rootValue,
+            $contextValue,
+            $operation,
+            $variableValues,
+            $errors,
+            $fieldResolver ?: self::$defaultFieldResolver
+        );
         return $exeContext;
     }
 
@@ -625,7 +654,7 @@ class Executor
         } else if (isset($parentType->resolveFieldFn)) {
             $resolveFn = $parentType->resolveFieldFn;
         } else {
-            $resolveFn = self::$defaultFieldResolver;
+            $resolveFn = $this->exeContext->fieldResolver;
         }
 
         // The resolve function's optional third argument is a context value that

src/GraphQL.php

@@ -17,16 +17,60 @@ use GraphQL\Validator\Rules\QueryComplexity;
 class GraphQL
 {
     /**
+     * This is the primary entry point function for fulfilling GraphQL operations
+     * by parsing, validating, and executing a GraphQL document along side a
+     * GraphQL schema.
+     *
+     * More sophisticated GraphQL servers, such as those which persist queries,
+     * may wish to separate the validation and execution phases to a static time
+     * tooling step, and a server runtime step.
+     *
+     * schema:
+     *    The GraphQL type system to use when validating and executing a query.
+     * requestString:
+     *    A GraphQL language formatted string representing the requested operation.
+     * rootValue:
+     *    The value provided as the first argument to resolver functions on the top
+     *    level type (e.g. the query object type).
+     * variableValues:
+     *    A mapping of variable name to runtime value to use for all variables
+     *    defined in the requestString.
+     * operationName:
+     *    The name of the operation to use if requestString contains multiple
+     *    possible operations. Can be omitted if requestString contains only
+     *    one operation.
+     * 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 or method on the source value with the field's name).
+     *
      * @param Schema $schema
      * @param string|DocumentNode $requestString
      * @param mixed $rootValue
      * @param array|null $variableValues
      * @param string|null $operationName
+     * @param callable $fieldResolver
      * @return Promise|array
      */
-    public static function execute(Schema $schema, $requestString, $rootValue = null, $contextValue = null, $variableValues = null, $operationName = null)
+    public static function execute(
+        Schema $schema,
+        $requestString,
+        $rootValue = null,
+        $contextValue = null,
+        $variableValues = null,
+        $operationName = null,
+        $fieldResolver = null
+    )
     {
-        $result = self::executeAndReturnResult($schema, $requestString, $rootValue, $contextValue, $variableValues, $operationName);
+        $result = self::executeAndReturnResult(
+            $schema,
+            $requestString,
+            $rootValue,
+            $contextValue,
+            $variableValues,
+            $operationName,
+            $fieldResolver
+        );
 
         if ($result instanceof ExecutionResult) {
             return $result->toArray();
@@ -40,14 +84,26 @@ class GraphQL
     }
 
     /**
+     * Same as `execute`, but returns instance of ExecutionResult instead of array,
+     * which can be used for custom error formatting or adding extensions to response
+     *
      * @param Schema $schema
      * @param string|DocumentNode $requestString
      * @param mixed $rootValue
      * @param array|null $variableValues
      * @param string|null $operationName
+     * @param callable $fieldResolver
      * @return ExecutionResult|Promise
      */
-    public static function executeAndReturnResult(Schema $schema, $requestString, $rootValue = null, $contextValue = null, $variableValues = null, $operationName = null)
+    public static function executeAndReturnResult(
+        Schema $schema,
+        $requestString,
+        $rootValue = null,
+        $contextValue = null,
+        $variableValues = null,
+        $operationName = null,
+        $fieldResolver = null
+    )
     {
         try {
             if ($requestString instanceof DocumentNode) {
@@ -66,7 +122,15 @@ class GraphQL
             if (!empty($validationErrors)) {
                 return new ExecutionResult(null, $validationErrors);
             } else {
-                return Executor::execute($schema, $documentNode, $rootValue, $contextValue, $variableValues, $operationName);
+                return Executor::execute(
+                    $schema,
+                    $documentNode,
+                    $rootValue,
+                    $contextValue,
+                    $variableValues,
+                    $operationName,
+                    $fieldResolver
+                );
             }
         } catch (Error $e) {
             return new ExecutionResult(null, [$e]);

tests/Executor/ExecutorTest.php

@@ -972,6 +972,44 @@ class ExecutorTest extends \PHPUnit_Framework_TestCase
         }
     }
 
+    /**
+     * @it uses a custom field resolver
+     */
+    public function testUsesACustomFieldResolver()
+    {
+        $query = Parser::parse('{ foo }');
+
+        $schema = new Schema([
+            'query' => new ObjectType([
+                'name' => 'Query',
+                'fields' => [
+                    'foo' => ['type' => Type::string()]
+                ]
+            ])
+        ]);
+
+        // For the purposes of test, just return the name of the field!
+        $customResolver = function ($source, $args, $context, ResolveInfo $info) {
+            return $info->fieldName;
+        };
+
+        $result = Executor::execute(
+            $schema,
+            $query,
+            null,
+            null,
+            null,
+            null,
+            $customResolver
+        );
+
+        $expected = [
+            'data' => ['foo' => 'foo']
+        ];
+
+        $this->assertEquals($expected, $result->toArray());
+    }
+
     public function testSubstitutesArgumentWithDefaultValue()
     {
         $schema = new Schema([