GraphQL @mock directive (#5836)

* Add mock directive
* Include tests for @mock directive

Author: davimacedo

Diff for: spec/ParseGraphQLServer.spec.js

@@ -5272,6 +5272,8 @@ describe('ParseGraphQLServer', () => {
             hello: String @resolve
             hello2: String @resolve(to: "hello")
             userEcho(user: _UserFields!): _UserClass! @resolve
+            hello3: String! @mock(with: "Hello world!")
+            hello4: _UserClass! @mock(with: { username: "somefolk" })
           }
         `,
       });
@@ -5357,5 +5359,35 @@ describe('ParseGraphQLServer', () => {
 
       expect(result.data.custom.userEcho.username).toEqual('somefolk');
     });
+
+    it('can mock a custom query with string', async () => {
+      const result = await apolloClient.query({
+        query: gql`
+          query Hello {
+            custom {
+              hello3
+            }
+          }
+        `,
+      });
+
+      expect(result.data.custom.hello3).toEqual('Hello world!');
+    });
+
+    it('can mock a custom query with auto type', async () => {
+      const result = await apolloClient.query({
+        query: gql`
+          query Hello {
+            custom {
+              hello4 {
+                username
+              }
+            }
+          }
+        `,
+      });
+
+      expect(result.data.custom.hello4.username).toEqual('somefolk');
+    });
   });
 });

Diff for: src/GraphQL/loaders/schemaDirectives.js

@@ -5,6 +5,7 @@ import { FunctionsRouter } from '../../Routers/FunctionsRouter';
 export const definitions = gql`
   directive @namespace on FIELD_DEFINITION
   directive @resolve(to: String) on FIELD_DEFINITION
+  directive @mock(with: Any!) on FIELD_DEFINITION
 `;
 
 const load = parseGraphQLSchema => {
@@ -46,6 +47,16 @@ const load = parseGraphQLSchema => {
   }
 
   parseGraphQLSchema.graphQLSchemaDirectives.resolve = ResolveDirectiveVisitor;
+
+  class MockDirectiveVisitor extends SchemaDirectiveVisitor {
+    visitFieldDefinition(field) {
+      field.resolve = () => {
+        return this.args.with;
+      };
+    }
+  }
+
+  parseGraphQLSchema.graphQLSchemaDirectives.mock = MockDirectiveVisitor;
 };
 
 export { load };