move @ReactMethod to the codegen'ed class so impl class don't need it anymore

Reviewed By: javache

Differential Revision: D5074121

fbshipit-source-id: 1b23a5d26ffe27c5093677ae7ecca424b232c8aa

Author: fkgozali

ReactAndroid/src/main/java/com/facebook/react/bridge/JavaModuleWrapper.java

@@ -78,7 +78,17 @@ private void findMethods() {
     Systrace.beginSection(TRACE_TAG_REACT_JAVA_BRIDGE, "findMethods");
     Set<String> methodNames = new HashSet<>();
 
-    Method[] targetMethods = mModuleClass.getDeclaredMethods();
+    Class<? extends NativeModule> classForMethods = mModuleClass;
+    Class<? extends NativeModule> superClass =
+        (Class<? extends NativeModule>) mModuleClass.getSuperclass();
+    if (ReactModuleWithSpec.class.isAssignableFrom(superClass)) {
+      // For java module that is based on generated flow-type spec, inspect the
+      // spec abstract class instead, which is the super class of the given java
+      // module.
+      classForMethods = superClass;
+    }
+    Method[] targetMethods = classForMethods.getDeclaredMethods();
+
     for (Method targetMethod : targetMethods) {
       ReactMethod annotation = targetMethod.getAnnotation(ReactMethod.class);
       if (annotation != null) {

ReactAndroid/src/main/java/com/facebook/react/bridge/ReactModuleWithSpec.java

@@ -0,0 +1,21 @@
+/**
+ * Copyright (c) 2015-present, Facebook, Inc.
+ * All rights reserved.
+ *
+ * This source code is licensed under the BSD-style license found in the
+ * LICENSE file in the root directory of this source tree. An additional grant
+ * of patent rights can be found in the PATENTS file in the same directory.
+ */
+
+package com.facebook.react.bridge;
+
+import com.facebook.proguard.annotations.DoNotStrip;
+
+/**
+ * An interface to be implemented by react modules that extends from the
+ * generated spec class.
+ * This is experimental.
+ */
+@DoNotStrip
+public interface ReactModuleWithSpec {
+}