From 052e578ed666f2749ec06d1d928bb622cada8841 Mon Sep 17 00:00:00 2001
From: Ramanpreet Nara <ramanpreet@fb.com>
Date: Fri, 6 Nov 2020 00:30:56 -0800
Subject: [PATCH] Set up experiment to dispatch promise methods asynchronously
 to NativeModules thread

Summary:
TurboModule methods that return promises are synchronously run on the JavaScript thread. Back in D22489338 (https://github.com/facebook/react-native/commit/9c35b5b8c4710dfe6a4b689a5565aa78ae5b37d3), we wrote code to make them dispatch on the NativeModules thread. That code, however, was just left disabled. In this diff, I wire up the TurboModules infra to a MobileConfig, which should allow us to assess the performance impact of async dispatch of promise methods to the NativeModules thread in production, before we roll it out more widely.

Changelog: [Internal]

Reviewed By: fkgozali

Differential Revision: D24685389

fbshipit-source-id: 8ceb2e6effc125abecfa76e5e90bd310676aefc9
---
 .../main/java/com/facebook/react/config/ReactFeatureFlags.java | 3 +++
 .../facebook/react/turbomodule/core/TurboModuleManager.java    | 3 ++-
 2 files changed, 5 insertions(+), 1 deletion(-)

diff --git a/ReactAndroid/src/main/java/com/facebook/react/config/ReactFeatureFlags.java b/ReactAndroid/src/main/java/com/facebook/react/config/ReactFeatureFlags.java
index 04a8a88eb5ca6d..9d8f1c4859a0d8 100644
--- a/ReactAndroid/src/main/java/com/facebook/react/config/ReactFeatureFlags.java
+++ b/ReactAndroid/src/main/java/com/facebook/react/config/ReactFeatureFlags.java
@@ -23,6 +23,9 @@ public class ReactFeatureFlags {
    */
   public static volatile boolean useTurboModules = false;
 
+  /** Should we dispatch TurboModule methods with promise returns to the NativeModules thread? */
+  public static volatile boolean enableTurboModulePromiseAsyncDispatch = false;
+
   /*
    * This feature flag enables logs for Fabric
    */
diff --git a/ReactAndroid/src/main/java/com/facebook/react/turbomodule/core/TurboModuleManager.java b/ReactAndroid/src/main/java/com/facebook/react/turbomodule/core/TurboModuleManager.java
index e6e6fcce69e099..8303d153f618db 100644
--- a/ReactAndroid/src/main/java/com/facebook/react/turbomodule/core/TurboModuleManager.java
+++ b/ReactAndroid/src/main/java/com/facebook/react/turbomodule/core/TurboModuleManager.java
@@ -17,6 +17,7 @@
 import com.facebook.react.bridge.JSIModule;
 import com.facebook.react.bridge.JavaScriptContextHolder;
 import com.facebook.react.bridge.NativeModule;
+import com.facebook.react.config.ReactFeatureFlags;
 import com.facebook.react.turbomodule.core.interfaces.CallInvokerHolder;
 import com.facebook.react.turbomodule.core.interfaces.TurboModule;
 import com.facebook.react.turbomodule.core.interfaces.TurboModuleRegistry;
@@ -60,7 +61,7 @@ public TurboModuleManager(
             (CallInvokerHolderImpl) jsCallInvokerHolder,
             (CallInvokerHolderImpl) nativeCallInvokerHolder,
             delegate,
-            false);
+            ReactFeatureFlags.enableTurboModulePromiseAsyncDispatch);
     installJSIBindings();
 
     mEagerInitModuleNames =