Resubmit: [react_native] 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.

Resubmit: previous version was reverted due to adsmanager crash

Reviewed By: foghina

Differential Revision: D2802899

fb-gh-sync-id: 3d850256fc22f7e9eb21fa71f6adb09cacc839c4

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;
@@ -46,6 +47,7 @@ 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;
@@ -242,6 +244,9 @@ import com.facebook.systrace.Systrace;
       NativeModuleCallExceptionHandler nativeModuleCallExceptionHandler) {
     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 +1,37 @@
+/**
+ * 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;
+  }
+
+  @DoNotStrip
+  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

@@ -782,6 +782,7 @@ extern "C" JNIEXPORT jint JNI_OnLoad(JavaVM* vm, void* reserved) {
     ReadableNativeArray::registerNatives();
     WritableNativeArray::registerNatives();
     JNativeRunnable::registerNatives();
+    registerJSLoaderNatives();
 
     registerNatives("com/facebook/react/bridge/NativeMap", {
         makeNativeMethod("initialize", map::initialize),