Fixed error in _getCallableModule method in MessageQueue

Reviewed By: javache

Differential Revision: D5208462

fbshipit-source-id: 13f71e2b7988305eccfa91c349ff120fad9129f0

Libraries/BatchedBridge/MessageQueue.js

@@ -152,7 +152,8 @@ class MessageQueue {
   }
 
   _getCallableModule(name: string) {
-    return this._lazyCallableModules[name]();
+    const getValue = this._lazyCallableModules[name];
+    return getValue ? getValue() : null;
   }
 
   enqueueNativeCall(moduleID: number, methodID: number, params: Array<any>, onFail: ?Function, onSucc: ?Function) {

Libraries/BatchedBridge/__tests__/MessageQueue-test.js

@@ -83,4 +83,33 @@ describe('MessageQueue', function() {
     queue.__invokeCallback(1);
     expect(() => queue.__invokeCallback(0)).toThrow();
   });
+
+  it('should throw when calling with unknown module', () => {
+    const unknownModule = 'UnknownModule', unknownMethod = 'UnknownMethod';
+    expect(() => queue.__callFunction(unknownModule, unknownMethod)).toThrow(
+      `Module ${unknownModule} is not a registered callable module (calling ${unknownMethod})`,
+    );
+  });
+
+  it('should return lazily registered module', () => {
+    const dummyModule = {}, name = 'modulesName';
+    queue.registerLazyCallableModule(name, () => dummyModule);
+    expect(queue._getCallableModule(name)).toEqual(dummyModule);
+  });
+
+  it('should not initialize lazily registered module before it was used for the first time', () => {
+    const dummyModule = {}, name = 'modulesName';
+    const factory = jest.fn(() => dummyModule);
+    queue.registerLazyCallableModule(name, factory);
+    expect(factory).not.toHaveBeenCalled();
+  });
+
+  it('should initialize lazily registered module only once', () => {
+    const dummyModule = {}, name = 'modulesName';
+    const factory = jest.fn(() => dummyModule);
+    queue.registerLazyCallableModule(name, factory);
+    queue._getCallableModule(name);
+    queue._getCallableModule(name);
+    expect(factory).toHaveBeenCalledTimes(1);
+  });
 });