From 02d2e85af36199c709158f5b1f77bb2bbbe7b3c9 Mon Sep 17 00:00:00 2001
From: Valentin Shergin <shergin@fb.com>
Date: Mon, 8 Oct 2018 14:34:22 -0700
Subject: [PATCH] Fabric: `failCallback` implementation for
 MessageQueueEventBeat

Summary: See comments in the code.

Reviewed By: mdvacca

Differential Revision: D10081502

fbshipit-source-id: b55bf019346a44c4b2980c70f547f53e4994e968
---
 React/Fabric/Utils/MessageQueueEventBeat.mm | 18 +++++++++++++++++-
 1 file changed, 17 insertions(+), 1 deletion(-)

diff --git a/React/Fabric/Utils/MessageQueueEventBeat.mm b/React/Fabric/Utils/MessageQueueEventBeat.mm
index c116755d8..49099f443 100644
--- a/React/Fabric/Utils/MessageQueueEventBeat.mm
+++ b/React/Fabric/Utils/MessageQueueEventBeat.mm
@@ -41,10 +41,26 @@ void MessageQueueEventBeat::induce() const {
     return;
   }
 
+#ifndef NDEBUG
+  // We do a trick here.
+  // If `wasExecuted` was destroyed before set to `true`,
+  // it means that the execution block was deallocated not being executed.
+  // This indicates that `messageQueueThread_` is being deallocated.
+  auto wasExecuted = std::shared_ptr<bool>(new bool {false}, [this](bool *wasExecuted) {
+    if (!*wasExecuted && failCallback_) {
+      failCallback_();
+    }
+    delete wasExecuted;
+  });
+#endif
+
   isBusy_ = true;
-  messageQueueThread_->runOnQueue([this]() {
+  messageQueueThread_->runOnQueue([=]() mutable {
     this->beat();
     isBusy_ = false;
+#ifndef NDEBUG
+    *wasExecuted = true;
+#endif
   });
 }