Expose way for native modules to modify JSC context

Reviewed By: svcscm

Differential Revision: D2933197

fb-gh-sync-id: 32eb943ab341804343bbcadd29f0377fccf75de6
shipit-source-id: 32eb943ab341804343bbcadd29f0377fccf75de6

React/Executors/RCTJSCExecutor.h

@@ -16,6 +16,15 @@
  */
 RCT_EXTERN NSString *const RCTJSCThreadName;
 
+/**
+ * This notification fires on the JS thread immediately after a `JSContext`
+ * is fully initialized, but before the JS bundle has been loaded. The object
+ * of this notification is the `JSContext`. Native modules should listen for
+ * notification only if they need to install custom functionality into the
+ * context. Note that this notification won't fire when debugging in Chrome.
+ */
+RCT_EXTERN NSString *const RCTJavaScriptContextCreatedNotification;
+
 /**
  * Uses a JavaScriptCore context as the execution engine.
  */

React/Executors/RCTJSCExecutor.m

@@ -28,6 +28,8 @@
 
 NSString *const RCTJSCThreadName = @"com.facebook.React.JavaScript";
 
+NSString *const RCTJavaScriptContextCreatedNotification = @"RCTJavaScriptContextCreatedNotification";
+
 static NSString *const RCTJSCProfilerEnabledDefaultsKey = @"RCTJSCProfilerEnabled";
 
 @interface RCTJavaScriptContext : NSObject <RCTInvalidating>
@@ -332,7 +334,16 @@ static void RCTInstallJSCProfiler(RCTBridge *bridge, JSContextRef context)
   }];
 
   [self executeBlockOnJavaScriptQueue:^{
-    RCTInstallJSCProfiler(_bridge, self.context.ctx);
+    RCTJSCExecutor *strongSelf = weakSelf;
+    if (!strongSelf.valid) {
+      return;
+    }
+
+    JSContext *context = strongSelf.context.context;
+    RCTInstallJSCProfiler(_bridge, context.JSGlobalContextRef);
+
+    [[NSNotificationCenter defaultCenter] postNotificationName:RCTJavaScriptContextCreatedNotification
+                                                        object:context];
   }];
 
   for (NSString *event in @[RCTProfileDidStartProfiling, RCTProfileDidEndProfiling]) {

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

@@ -332,6 +332,11 @@ public abstract class BaseJavaModule implements NativeModule {
     return false;
   }
 
+  @Override
+  public void onReactBridgeInitialized(ReactBridge bridge) {
+    // do nothing
+  }
+
   @Override
   public void onCatalystInstanceDestroy() {
     // do nothing

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

@@ -127,6 +127,7 @@ public class CatalystInstanceImpl implements CatalystInstance {
       Systrace.endSection(Systrace.TRACE_TAG_REACT_JAVA_BRIDGE);
     }
 
+    mJavaRegistry.notifyReactBridgeInitialized(bridge);
     return bridge;
   }
 

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

@@ -59,6 +59,15 @@ public interface NativeModule {
    */
   boolean canOverrideExistingModule();
 
+  /**
+   * Called on the JS thread after a ReactBridge has been created. This is useful for native modules
+   * that need to do any setup before the JS bundle has been loaded. An example of this would be
+   * installing custom functionality into the JavaScriptCore context.
+   *
+   * @param bridge the ReactBridge instance that has just been created
+   */
+  void onReactBridgeInitialized(ReactBridge bridge);
+
   /**
    * Called before {CatalystInstance#onHostDestroy}
    */

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

@@ -114,6 +114,19 @@ public class NativeModuleRegistry {
     }
   }
 
+  /* package */ void notifyReactBridgeInitialized(ReactBridge bridge) {
+    Systrace.beginSection(
+        Systrace.TRACE_TAG_REACT_JAVA_BRIDGE,
+        "NativeModuleRegistry_notifyReactBridgeInitialized");
+    try {
+      for (NativeModule nativeModule : mModuleInstances.values()) {
+        nativeModule.onReactBridgeInitialized(bridge);
+      }
+    } finally {
+      Systrace.endSection(Systrace.TRACE_TAG_REACT_JAVA_BRIDGE);
+    }
+  }
+
   public void onBatchComplete() {
     for (int i = 0; i < mBatchCompleteListenerModules.size(); i++) {
       mBatchCompleteListenerModules.get(i).onBatchComplete();

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

@@ -87,4 +87,13 @@ public class ReactBridge extends Countable {
   public native void stopProfiler(String title, String filename);
   private native void handleMemoryPressureModerate();
   private native void handleMemoryPressureCritical();
+
+  /**
+   * This method will return a long representing the underlying JSGlobalContextRef pointer or
+   * 0 (representing NULL) when in Chrome debug mode, and is only useful if passed back through
+   * the JNI to native code that will use it with the JavaScriptCore C API.
+   * **WARNING:** This method is *experimental* and should only be used when no other option is
+   * available. It will likely change in a future release!
+   */
+  public native long getJavaScriptContextNativePtrExperimental();
 }

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

@@ -57,6 +57,10 @@ void Bridge::setGlobalVariable(const std::string& propName, const std::string& j
   m_mainExecutor->setGlobalVariable(propName, jsonValue);
 }
 
+void* Bridge::getJavaScriptContext() {
+  return m_mainExecutor->getJavaScriptContext();
+}
+
 bool Bridge::supportsProfiling() {
   return m_mainExecutor->supportsProfiling();
 }

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

@@ -54,6 +54,7 @@ public:
     const std::string& startupCode,
     const std::string& sourceURL);
   void setGlobalVariable(const std::string& propName, const std::string& jsonValue);
+  void* getJavaScriptContext();
   bool supportsProfiling();
   void startProfiler(const std::string& title);
   void stopProfiler(const std::string& title, const std::string& filename);

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

@@ -60,6 +60,9 @@ public:
   virtual void setGlobalVariable(
     const std::string& propName,
     const std::string& jsonValue) = 0;
+  virtual void* getJavaScriptContext() {
+    return nullptr;
+  };
   virtual bool supportsProfiling() {
     return false;
   };

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

@@ -198,6 +198,10 @@ void JSCExecutor::setGlobalVariable(const std::string& propName, const std::stri
   JSObjectSetProperty(m_context, globalObject, jsPropertyName, valueToInject, 0, NULL);
 }
 
+void* JSCExecutor::getJavaScriptContext() {
+  return m_context;
+}
+
 bool JSCExecutor::supportsProfiling() {
   #ifdef WITH_FBSYSTRACE
   return true;

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

@@ -48,6 +48,7 @@ public:
   virtual void setGlobalVariable(
     const std::string& propName,
     const std::string& jsonValue) override;
+  virtual void* getJavaScriptContext() override;
   virtual bool supportsProfiling() override;
   virtual void startProfiler(const std::string &titleString) override;
   virtual void stopProfiler(const std::string &titleString, const std::string &filename) override;

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

@@ -760,6 +760,11 @@ static void setGlobalVariable(JNIEnv* env, jobject obj, jstring propName, jstrin
   bridge->setGlobalVariable(fromJString(env, propName), fromJString(env, jsonValue));
 }
 
+static jlong getJavaScriptContext(JNIEnv *env, jobject obj) {
+  auto bridge = extractRefPtr<CountableBridge>(env, obj);
+  return (uintptr_t) bridge->getJavaScriptContext();
+}
+
 static jboolean supportsProfiling(JNIEnv* env, jobject obj) {
   auto bridge = extractRefPtr<CountableBridge>(env, obj);
   return bridge->supportsProfiling() ? JNI_TRUE : JNI_FALSE;
@@ -944,7 +949,7 @@ extern "C" JNIEXPORT jint JNI_OnLoad(JavaVM* vm, void* reserved) {
         makeNativeMethod("stopProfiler", bridge::stopProfiler),
         makeNativeMethod("handleMemoryPressureModerate", bridge::handleMemoryPressureModerate),
         makeNativeMethod("handleMemoryPressureCritical", bridge::handleMemoryPressureCritical),
-
+        makeNativeMethod("getJavaScriptContextNativePtrExperimental", bridge::getJavaScriptContext),
     });
 
     jclass nativeRunnableClass = env->FindClass("com/facebook/react/bridge/queue/NativeRunnableDeprecated");