From 0735873fbcdf7914ac63ae651e9118a9530d528b Mon Sep 17 00:00:00 2001
From: Marc Horowitz <mhorowitz@fb.com>
Date: Wed, 17 Apr 2019 21:17:51 -0700
Subject: [PATCH] Make isInspectable safe to call from any thread

Summary: The bridge was not properly isolating isInspectable onto the JS thread.

Reviewed By: fkgozali

Differential Revision: D14991970

fbshipit-source-id: 92a06c90bade8f92bfa81fa3b7dfb23b17db6117
---
 ReactCommon/cxxreact/NativeToJsBridge.cpp | 13 +++++++------
 ReactCommon/cxxreact/NativeToJsBridge.h   |  5 +++++
 2 files changed, 12 insertions(+), 6 deletions(-)

diff --git a/ReactCommon/cxxreact/NativeToJsBridge.cpp b/ReactCommon/cxxreact/NativeToJsBridge.cpp
index 27c54a3739c..2c3893e87e6 100644
--- a/ReactCommon/cxxreact/NativeToJsBridge.cpp
+++ b/ReactCommon/cxxreact/NativeToJsBridge.cpp
@@ -84,14 +84,15 @@ private:
 };
 
 NativeToJsBridge::NativeToJsBridge(
-    JSExecutorFactory* jsExecutorFactory,
+    JSExecutorFactory *jsExecutorFactory,
     std::shared_ptr<ModuleRegistry> registry,
     std::shared_ptr<MessageQueueThread> jsQueue,
     std::shared_ptr<InstanceCallback> callback)
-    : m_destroyed(std::make_shared<bool>(false))
-    , m_delegate(std::make_shared<JsToNativeBridge>(registry, callback))
-    , m_executor(jsExecutorFactory->createJSExecutor(m_delegate, jsQueue))
-    , m_executorMessageQueueThread(std::move(jsQueue)) {}
+    : m_destroyed(std::make_shared<bool>(false)),
+      m_delegate(std::make_shared<JsToNativeBridge>(registry, callback)),
+      m_executor(jsExecutorFactory->createJSExecutor(m_delegate, jsQueue)),
+      m_executorMessageQueueThread(std::move(jsQueue)),
+      m_inspectable(m_executor->isInspectable()) {}
 
 // This must be called on the same thread on which the constructor was called.
 NativeToJsBridge::~NativeToJsBridge() {
@@ -225,7 +226,7 @@ void* NativeToJsBridge::getJavaScriptContext() {
 }
 
 bool NativeToJsBridge::isInspectable() {
-  return m_executor->isInspectable();
+  return m_inspectable;
 }
   
 bool NativeToJsBridge::isBatchActive() {
diff --git a/ReactCommon/cxxreact/NativeToJsBridge.h b/ReactCommon/cxxreact/NativeToJsBridge.h
index c80114230e8..bf5746a0e7f 100644
--- a/ReactCommon/cxxreact/NativeToJsBridge.h
+++ b/ReactCommon/cxxreact/NativeToJsBridge.h
@@ -96,6 +96,11 @@ private:
   std::unique_ptr<JSExecutor> m_executor;
   std::shared_ptr<MessageQueueThread> m_executorMessageQueueThread;
 
+  // Memoize this on the JS thread, so that it can be inspected from
+  // any thread later.  This assumes inspectability doesn't change for
+  // a JSExecutor instance, which is true for all existing implementations.
+  bool m_inspectable;
+
   // Keep track of whether the JS bundle containing the application logic causes
   // exception when evaluated initially. If so, more calls to JS will very
   // likely fail as well, so this flag can help prevent them.