Add Java Turbo Module Event Emitter example (facebook#44906)

Summary:
Pull Request resolved: facebook#44906

Shows a proof of concept how '*strongly typed Turbo Module scoped*' `EventEmitters` can be used in a Java Turbo Module.

## Changelog:

[Android] [Added] - Add Java Turbo Module Event Emitter example

Reviewed By: javache

Differential Revision: D57530807

Author: christophpurrer

packages/react-native-codegen/src/parsers/error-utils.js

@@ -164,17 +164,15 @@ function throwIfEventEmitterTypeIsUnsupported(
   parser: Parser,
   nullable: boolean,
   untyped: boolean,
-  cxxOnly: boolean,
 ) {
-  if (nullable || untyped || !cxxOnly) {
+  if (nullable || untyped) {
     throw new UnsupportedModuleEventEmitterPropertyParserError(
       nativeModuleName,
       propertyName,
       propertyValueType,
       parser.language(),
       nullable,
       untyped,
-      cxxOnly,
     );
   }
 }

packages/react-native-codegen/src/parsers/errors.js

@@ -100,15 +100,12 @@ class UnsupportedModuleEventEmitterPropertyParserError extends ParserError {
     language: ParserType,
     nullable: boolean,
     untyped: boolean,
-    cxxOnly: boolean,
   ) {
     let message = `${language} interfaces extending TurboModule must only contain 'FunctionTypeAnnotation's or non nullable 'EventEmitter's. Further the EventEmitter property `;
     if (nullable) {
       message += `'${propertyValue}' must non nullable.`;
     } else if (untyped) {
       message += `'${propertyValue}' must have a concrete or void eventType.`;
-    } else if (cxxOnly) {
-      message += `'${propertyValue}' is only supported in C++ Turbo Modules.`;
     }
     super(nativeModuleName, propertyValue, message);
   }

packages/react-native-codegen/src/parsers/parsers-commons.js

@@ -506,7 +506,6 @@ function buildEventEmitterSchema(
     parser,
     typeAnnotationNullable,
     typeAnnotationUntyped,
-    cxxOnly,
   );
   const eventTypeResolutionStatus = resolveTypeAnnotationFN(
     typeAnnotation.typeParameters.params[0],

packages/react-native/ReactAndroid/src/main/java/com/facebook/react/bridge/BaseJavaModule.java

@@ -13,6 +13,7 @@
 import com.facebook.common.logging.FLog;
 import com.facebook.infer.annotation.Assertions;
 import com.facebook.infer.annotation.ThreadConfined;
+import com.facebook.proguard.annotations.DoNotStrip;
 import com.facebook.react.common.ReactConstants;
 import com.facebook.react.common.annotations.DeprecatedInNewArchitecture;
 import com.facebook.react.common.annotations.StableReactNativeAPI;
@@ -54,6 +55,8 @@ public abstract class BaseJavaModule implements NativeModule {
   public static final String METHOD_TYPE_PROMISE = "promise";
   public static final String METHOD_TYPE_SYNC = "sync";
 
+  @Nullable protected CxxCallbackImpl mEventEmitterCallback;
+
   private final @Nullable ReactApplicationContext mReactApplicationContext;
 
   public BaseJavaModule() {
@@ -129,4 +132,9 @@ protected final ReactApplicationContext getReactApplicationContext() {
     }
     return null;
   }
+
+  @DoNotStrip
+  private final void setEventEmitterCallback(CxxCallbackImpl eventEmitterCallback) {
+    mEventEmitterCallback = eventEmitterCallback;
+  }
 }

packages/react-native/ReactCommon/react/nativemodule/core/platform/android/ReactCommon/JavaTurboModule.cpp

@@ -992,4 +992,34 @@ jsi::Value JavaTurboModule::invokeJavaMethod(
   }
 }
 
+void JavaTurboModule::setEventEmitterCallback(
+    jni::alias_ref<jobject> jinstance) {
+  JNIEnv* env = jni::Environment::current();
+  auto instance = jinstance.get();
+  static jmethodID cachedMethodId = nullptr;
+  if (cachedMethodId == nullptr) {
+    jclass cls = env->GetObjectClass(instance);
+    cachedMethodId = env->GetMethodID(
+        cls,
+        "setEventEmitterCallback",
+        "(Lcom/facebook/react/bridge/CxxCallbackImpl;)V");
+  }
+
+  auto eventEmitterLookup =
+      [&](const std::string& eventName) -> AsyncEventEmitter<folly::dynamic>& {
+    return static_cast<AsyncEventEmitter<folly::dynamic>&>(
+        *eventEmitterMap_[eventName].get());
+  };
+
+  jvalue arg;
+  arg.l = JCxxCallbackImpl::newObjectCxxArgs([eventEmitterLookup = std::move(
+                                                  eventEmitterLookup)](
+                                                 folly::dynamic args) {
+            auto eventName = args.at(0).asString();
+            auto eventArgs = args.size() > 1 ? args.at(1) : nullptr;
+            eventEmitterLookup(eventName).emit(std::move(eventArgs));
+          }).release();
+  env->CallVoidMethod(instance, cachedMethodId, arg);
+}
+
 } // namespace facebook::react

packages/react-native/ReactCommon/react/nativemodule/core/platform/android/ReactCommon/JavaTurboModule.h

@@ -51,6 +51,8 @@ class JSI_EXPORT JavaTurboModule : public TurboModule {
       size_t argCount,
       jmethodID& cachedMethodID);
 
+  void setEventEmitterCallback(jni::alias_ref<jobject> instance);
+
  private:
   // instance_ can be of type JTurboModule, or JNativeModule
   jni::global_ref<jobject> instance_;

packages/react-native/ReactCommon/react/nativemodule/samples/platform/android/NativeSampleTurboModuleSpec.java

@@ -35,6 +35,22 @@ public NativeSampleTurboModuleSpec(ReactApplicationContext reactContext) {
     super(reactContext);
   }
 
+  protected final void emitOnPress() {
+    mEventEmitterCallback.invoke("onPress");
+  }
+
+  protected final void emitOnClick(String value) {
+    mEventEmitterCallback.invoke("onClick", value);
+  }
+
+  protected final void emitOnChange(ReadableMap value) {
+    mEventEmitterCallback.invoke("onChange", value);
+  }
+
+  protected void emitOnSubmit(ReadableArray value) {
+    mEventEmitterCallback.invoke("onSubmit", value);
+  }
+
   @Override
   public @Nonnull String getName() {
     return NAME;

packages/react-native/ReactCommon/react/nativemodule/samples/platform/android/ReactCommon/SampleTurboModuleSpec.cpp

@@ -351,6 +351,15 @@ NativeSampleTurboModuleSpecJSI::NativeSampleTurboModuleSpecJSI(
       1, __hostFunction_NativeSampleTurboModuleSpecJSI_getObjectAssert};
   methodMap_["promiseAssert"] = MethodMetadata{
       0, __hostFunction_NativeSampleTurboModuleSpecJSI_promiseAssert};
+  eventEmitterMap_["onPress"] =
+      std::make_shared<AsyncEventEmitter<folly::dynamic>>();
+  eventEmitterMap_["onClick"] =
+      std::make_shared<AsyncEventEmitter<folly::dynamic>>();
+  eventEmitterMap_["onChange"] =
+      std::make_shared<AsyncEventEmitter<folly::dynamic>>();
+  eventEmitterMap_["onSubmit"] =
+      std::make_shared<AsyncEventEmitter<folly::dynamic>>();
+  setEventEmitterCallback(params.instance);
 }
 
 std::shared_ptr<TurboModule> SampleTurboModuleSpec_ModuleProvider(

packages/react-native/ReactCommon/react/nativemodule/samples/platform/android/SampleTurboModule.java

@@ -104,7 +104,26 @@ public double getRootTag(double arg) {
   @Override
   public void voidFunc() {
     log("voidFunc", "<void>", "<void>");
-    return;
+    emitOnPress();
+    emitOnClick("click");
+    {
+      WritableNativeMap map = new WritableNativeMap();
+      map.putInt("a", 1);
+      map.putString("b", "two");
+      emitOnChange(map);
+    }
+    {
+      WritableNativeArray array = new WritableNativeArray();
+      WritableNativeMap map = new WritableNativeMap();
+      map.putInt("a", 1);
+      map.putString("b", "two");
+      array.pushMap(map);
+      WritableNativeMap map1 = new WritableNativeMap();
+      map1.putInt("a", 3);
+      map1.putString("b", "four");
+      array.pushMap(map1);
+      emitOnSubmit(array);
+    }
   }
 
   // This function returns {@link WritableMap} instead of {@link Map} for backward compat with

packages/react-native/src/private/specs/modules/NativeSampleTurboModule.js

@@ -12,7 +12,10 @@ import type {
   RootTag,
   TurboModule,
 } from '../../../../Libraries/TurboModule/RCTExport';
-import type {UnsafeObject} from '../../../../Libraries/Types/CodegenTypes';
+import type {
+  EventEmitter,
+  UnsafeObject,
+} from '../../../../Libraries/Types/CodegenTypes';
 
 import * as TurboModuleRegistry from '../../../../Libraries/TurboModule/TurboModuleRegistry';
 
@@ -21,7 +24,17 @@ export enum EnumInt {
   B = 42,
 }
 
+export type ObjectStruct = {
+  a: number,
+  b: string,
+  c?: ?string,
+};
+
 export interface Spec extends TurboModule {
+  +onPress: EventEmitter<void>;
+  +onClick: EventEmitter<string>;
+  +onChange: EventEmitter<ObjectStruct>;
+  +onSubmit: EventEmitter<ObjectStruct[]>;
   // Exported methods.
   +getConstants: () => {|
     const1: boolean,