improve default fn behavior (#468)

Author: Kevin Lacker

src/execution/__tests__/resolve-test.js

@@ -66,6 +66,34 @@ describe('Execute: resolve function', () => {
     });
   });
 
+  it('default function passes args and context', async () => {
+    const schema = testSchema({
+      type: GraphQLInt,
+      args: {
+        addend1: { type: GraphQLInt },
+      },
+    });
+
+    class Adder {
+      constructor(num) {
+        this._num = num;
+      }
+
+      test({addend1}, context) {
+        return this._num + addend1 + context.addend2;
+      }
+    }
+    const source = new Adder(700);
+
+    expect(
+      await graphql(schema, '{ test(addend1: 80) }', source, { addend2: 9 })
+    ).to.deep.equal({
+      data: {
+        test: 789
+      }
+    });
+  });
+
   it('uses provided resolve function', async () => {
     const schema = testSchema({
       type: GraphQLString,

src/execution/execute.js

@@ -990,13 +990,16 @@ function defaultResolveTypeFn(
  * If a resolve function is not given, then a default resolve behavior is used
  * which takes the property of the source object of the same name as the field
  * and returns it as the result, or if it's a function, returns the result
- * of calling that function.
+ * of calling that function while passing along args and context.
  */
 function defaultResolveFn(source: any, args, context, { fieldName }) {
   // ensure source is a value for which property access is acceptable.
   if (typeof source === 'object' || typeof source === 'function') {
     const property = source[fieldName];
-    return typeof property === 'function' ? source[fieldName]() : property;
+    if (typeof property === 'function') {
+      return source[fieldName](args, context);
+    }
+    return property;
   }
 }