WebWorkers: Add JSLoader API for loading script from assets with AssetLoader reference

Summary:
public

Adds the ability to load files from assets without threading through an AssetManager. After the bridge is unforked, we should move to passing through an Environment object instead.

Reviewed By: lexs

Differential Revision: D2779079

fb-gh-sync-id: 82b47ecdf48b724076d87f4879ec40601e21e6bc

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

@@ -17,6 +17,7 @@ import java.util.List;
 import java.util.concurrent.ConcurrentLinkedQueue;
 
 import android.app.Activity;
+import android.app.Application;
 import android.content.Context;
 import android.content.Intent;
 import android.os.AsyncTask;
@@ -45,6 +46,7 @@ import com.facebook.react.bridge.UiThreadUtil;
 import com.facebook.react.bridge.WritableMap;
 import com.facebook.react.bridge.WritableNativeMap;
 import com.facebook.react.bridge.queue.CatalystQueueConfigurationSpec;
+import com.facebook.react.common.ApplicationHolder;
 import com.facebook.react.common.ReactConstants;
 import com.facebook.react.common.annotations.VisibleForTesting;
 import com.facebook.react.devsupport.DevServerHelper;
@@ -199,6 +201,9 @@ import com.facebook.systrace.Systrace;
       UIImplementationProvider uiImplementationProvider) {
     initializeSoLoaderIfNecessary(applicationContext);
 
+    // TODO(9577825): remove this
+    ApplicationHolder.setApplication((Application) applicationContext.getApplicationContext());
+
     mApplicationContext = applicationContext;
     mJSBundleFile = jsBundleFile;
     mJSMainModuleName = jsMainModuleName;

ReactAndroid/src/main/java/com/facebook/react/common/ApplicationHolder.java

@@ -0,0 +1,36 @@
+/**
+ * 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.common;
+
+import android.app.Application;
+
+import com.facebook.infer.annotation.Assertions;
+import com.facebook.proguard.annotations.DoNotStrip;
+
+/**
+ * Holds the current Application Object.
+ *
+ * TODO(9577825): This is a bad pattern, we should thread through an Environment object instead.
+ * Remove once bridge is unforked.
+ */
+@DoNotStrip
+@Deprecated
+public class ApplicationHolder {
+
+  private static Application sApplication;
+
+  public static void setApplication(Application application) {
+    sApplication = application;
+  }
+
+  public static Application getApplication() {
+    return Assertions.assertNotNull(sApplication);
+  }
+}

ReactAndroid/src/main/jni/react/jni/JSLoader.cpp

@@ -4,6 +4,7 @@
 
 #include <android/asset_manager.h>
 #include <android/asset_manager_jni.h>
+#include <jni/Environment.h>
 #include <fstream>
 #include <sstream>
 #include <streambuf>
@@ -18,6 +19,19 @@ using fbsystrace::FbSystraceSection;
 namespace facebook {
 namespace react {
 
+static jclass gApplicationHolderClass;
+static jmethodID gGetApplicationMethod;
+static jmethodID gGetAssetManagerMethod;
+
+std::string loadScriptFromAssets(std::string assetName) {
+  JNIEnv *env = jni::Environment::current();
+  jobject application = env->CallStaticObjectMethod(
+    gApplicationHolderClass,
+    gGetApplicationMethod);
+  jobject assetManager = env->CallObjectMethod(application, gGetAssetManagerMethod);
+  return loadScriptFromAssets(env, assetManager, assetName);
+}
+
 std::string loadScriptFromAssets(
     JNIEnv *env,
     jobject assetManager,
@@ -71,4 +85,14 @@ std::string loadScriptFromFile(std::string fileName) {
   return "";
 }
 
-} }
+void registerJSLoaderNatives() {
+  JNIEnv *env = jni::Environment::current();
+  jclass applicationHolderClass = env->FindClass("com/facebook/react/common/ApplicationHolder");
+  gApplicationHolderClass = (jclass)env->NewGlobalRef(applicationHolderClass);
+  gGetApplicationMethod = env->GetStaticMethodID(applicationHolderClass, "getApplication", "()Landroid/app/Application;");
+  
+  jclass appClass = env->FindClass("android/app/Application");
+  gGetAssetManagerMethod = env->GetMethodID(appClass, "getAssets", "()Landroid/content/res/AssetManager;");
+}
+
+} }

ReactAndroid/src/main/jni/react/jni/JSLoader.h

@@ -8,6 +8,12 @@
 namespace facebook {
 namespace react {
 
+/**
+ * Helper method for loading a JS script from Android assets without
+ * a reference to an AssetManager.
+ */
+std::string loadScriptFromAssets(std::string assetName);
+
 /**
  * Helper method for loading JS script from android asset
  */
@@ -18,4 +24,6 @@ std::string loadScriptFromAssets(JNIEnv *env, jobject assetManager, std::string
  */
 std::string loadScriptFromFile(std::string fileName);
 
+void registerJSLoaderNatives();
+
 } }

ReactAndroid/src/main/jni/react/jni/OnLoad.cpp

@@ -780,6 +780,7 @@ extern "C" JNIEXPORT jint JNI_OnLoad(JavaVM* vm, void* reserved) {
     NativeArray::registerNatives();
     ReadableNativeArray::registerNatives();
     WritableNativeArray::registerNatives();
+    registerJSLoaderNatives();
 
     registerNatives("com/facebook/react/bridge/NativeMap", {
         makeNativeMethod("initialize", map::initialize),