From 29bbab5a5a160411424c8ac13cc5ba5e65caaf28 Mon Sep 17 00:00:00 2001
From: =?UTF-8?q?Rub=C3=A9n=20Norte?= <rubennorte@meta.com>
Date: Wed, 18 Oct 2023 06:14:25 -0700
Subject: [PATCH] Clean up old and unused implementation of microtasks (#40870)

Summary:
Pull Request resolved: https://github.com/facebook/react-native/pull/40870

This removes an old experiment to implement microtasks in React Native (which is incorrect now that the runtime scheduler executes multiple tasks per runtime executor "task"). `drainMicrotasks` is a no-op at the moment in Hermes because the flag isn't set, so this code is essentially dead.

We'll add the new iteration of microtasks in a following PR.

Changelog: [internal]

Reviewed By: christophpurrer

Differential Revision: D49536251

fbshipit-source-id: b8efba2d0310b9e33e65b79c60ad2db1c8109def
---
 .../jsiexecutor/jsireact/JSIExecutor.cpp      | 30 -------------------
 .../react/runtime/ReactInstance.cpp           | 25 ----------------
 2 files changed, 55 deletions(-)

diff --git a/packages/react-native/ReactCommon/jsiexecutor/jsireact/JSIExecutor.cpp b/packages/react-native/ReactCommon/jsiexecutor/jsireact/JSIExecutor.cpp
index 279e45a056..51fabddc8f 100644
--- a/packages/react-native/ReactCommon/jsiexecutor/jsireact/JSIExecutor.cpp
+++ b/packages/react-native/ReactCommon/jsiexecutor/jsireact/JSIExecutor.cpp
@@ -208,30 +208,6 @@ void JSIExecutor::registerBundle(
       ReactMarker::REGISTER_JS_SEGMENT_STOP, tag.c_str());
 }
 
-// Looping on \c drainMicrotasks until it completes or hits the retries bound.
-static void performMicrotaskCheckpoint(jsi::Runtime& runtime) {
-  uint8_t retries = 0;
-  // A heuristic number to guard infinite or absurd numbers of retries.
-  const static unsigned int kRetriesBound = 255;
-
-  while (retries < kRetriesBound) {
-    try {
-      // The default behavior of \c drainMicrotasks is unbounded execution.
-      // We may want to make it bounded in the future.
-      if (runtime.drainMicrotasks()) {
-        break;
-      }
-    } catch (jsi::JSError& error) {
-      handleJSError(runtime, error, true);
-    }
-    retries++;
-  }
-
-  if (retries == kRetriesBound) {
-    throw std::runtime_error("Hits microtasks retries bound.");
-  }
-}
-
 void JSIExecutor::callFunction(
     const std::string& moduleId,
     const std::string& methodId,
@@ -267,8 +243,6 @@ void JSIExecutor::callFunction(
         std::runtime_error("Error calling " + moduleId + "." + methodId));
   }
 
-  performMicrotaskCheckpoint(*runtime_);
-
   callNativeModules(ret, true);
 }
 
@@ -288,8 +262,6 @@ void JSIExecutor::invokeCallback(
         folly::to<std::string>("Error invoking callback ", callbackId)));
   }
 
-  performMicrotaskCheckpoint(*runtime_);
-
   callNativeModules(ret, true);
 }
 
@@ -426,7 +398,6 @@ void JSIExecutor::flush() {
   SystraceSection s("JSIExecutor::flush");
   if (flushedQueue_) {
     Value ret = flushedQueue_->call(*runtime_);
-    performMicrotaskCheckpoint(*runtime_);
     callNativeModules(ret, true);
     return;
   }
@@ -444,7 +415,6 @@ void JSIExecutor::flush() {
     // get the pending queue of native calls.
     bindBridge();
     Value ret = flushedQueue_->call(*runtime_);
-    performMicrotaskCheckpoint(*runtime_);
     callNativeModules(ret, true);
   } else if (delegate_) {
     // If we have a delegate, we need to call it; we pass a null list to
diff --git a/packages/react-native/ReactCommon/react/runtime/ReactInstance.cpp b/packages/react-native/ReactCommon/react/runtime/ReactInstance.cpp
index 0f85cf0b72..abfda3b74a 100644
--- a/packages/react-native/ReactCommon/react/runtime/ReactInstance.cpp
+++ b/packages/react-native/ReactCommon/react/runtime/ReactInstance.cpp
@@ -24,30 +24,6 @@
 
 namespace facebook::react {
 
-// Looping on \c drainMicrotasks until it completes or hits the retries bound.
-static void performMicrotaskCheckpoint(jsi::Runtime& runtime) {
-  uint8_t retries = 0;
-  // A heuristic number to guard inifinite or absurd numbers of retries.
-  constexpr unsigned int kRetriesBound = 255;
-
-  while (retries < kRetriesBound) {
-    try {
-      // The default behavior of \c drainMicrotasks is unbounded execution.
-      // We may want to make it bounded in the future.
-      if (runtime.drainMicrotasks()) {
-        break;
-      }
-    } catch (jsi::JSError& error) {
-      handleJSError(runtime, error, true);
-    }
-    retries++;
-  }
-
-  if (retries == kRetriesBound) {
-    throw std::runtime_error("Hits microtasks retries bound.");
-  }
-}
-
 ReactInstance::ReactInstance(
     std::unique_ptr<jsi::Runtime> runtime,
     std::shared_ptr<MessageQueueThread> jsMessageQueueThread,
@@ -91,7 +67,6 @@ ReactInstance::ReactInstance(
                 if (auto strongTimerManager = weakTimerManager.lock()) {
                   strongTimerManager->callReactNativeMicrotasks(*strongRuntime);
                 }
-                performMicrotaskCheckpoint(*strongRuntime);
               } catch (jsi::JSError& originalError) {
                 handleJSError(*strongRuntime, originalError, true);
               }