Add LazyReactPackage

Summary:
LazyReactPackage is an extension of ReactPackage that allows us to lazily construct native modules.
It's a separate class to avoid breaking existing packages both internally and in open source.

Reviewed By: astreet

Differential Revision: D3334258

fbshipit-source-id: e090e146adc4e8e156cae217689e2258ab9837aa

ReactAndroid/src/main/java/com/facebook/react/LazyReactPackage.java

@@ -0,0 +1,40 @@
+/**
+ * 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;
+
+import java.util.ArrayList;
+import java.util.List;
+
+import com.facebook.react.bridge.ModuleSpec;
+import com.facebook.react.bridge.NativeModule;
+import com.facebook.react.bridge.ReactApplicationContext;
+
+/**
+ * React package supporting lazy creation of native modules.
+ *
+ * TODO(t11394819): Make this default and deprecate ReactPackage
+ */
+public abstract class LazyReactPackage implements ReactPackage {
+  /**
+   * @param reactContext react application context that can be used to create modules
+   * @return list of module specs that can create the native modules
+   */
+  public abstract List<ModuleSpec> getNativeModules(
+    ReactApplicationContext reactContext);
+
+  @Override
+  public final List<NativeModule> createNativeModules(ReactApplicationContext reactContext) {
+    List<NativeModule> modules = new ArrayList<>();
+    for (ModuleSpec holder : getNativeModules(reactContext)) {
+      modules.add(holder.getProvider().get());
+    }
+    return modules;
+  }
+}