From a60b74d974360092008648c58a7fc125fccad3c3 Mon Sep 17 00:00:00 2001
From: Marc Horowitz <mhorowitz@fb.com>
Date: Thu, 16 Jun 2016 14:28:28 -0700
Subject: [PATCH] When executing JS throws an exception, capture the js stack
 in the C++ exception thrown

Reviewed By: davidaurelio

Differential Revision: D3428921

fbshipit-source-id: 0e8be84a2be92558ea3de0d32d1d4a53308d8270
---
 ReactCommon/cxxreact/JSCHelpers.cpp | 13 +++++++++++--
 ReactCommon/cxxreact/JSCHelpers.h   | 27 +++++++++++++++++++++++----
 2 files changed, 34 insertions(+), 6 deletions(-)

diff --git a/ReactCommon/cxxreact/JSCHelpers.cpp b/ReactCommon/cxxreact/JSCHelpers.cpp
index f30d9dbfb..d0aa0a0ed 100644
--- a/ReactCommon/cxxreact/JSCHelpers.cpp
+++ b/ReactCommon/cxxreact/JSCHelpers.cpp
@@ -52,7 +52,8 @@ JSValueRef evaluateScript(JSContextRef context, JSStringRef script, JSStringRef
     // file/resource, or was a constructed statement.  The location
     // info will include that source, if any.
     std::string locationInfo = source != nullptr ? String::ref(source).str() : "";
-    auto line = exception.asObject().getProperty("line");
+    Object exObject = exception.asObject();
+    auto line = exObject.getProperty("line");
     if (line != nullptr && line.isNumber()) {
       if (locationInfo.empty() && line.asInteger() != 1) {
         // If there is a non-trivial line number, but there was no
@@ -71,7 +72,15 @@ JSValueRef evaluateScript(JSContextRef context, JSStringRef script, JSStringRef
     }
 
     LOG(ERROR) << "Got JS Exception: " << exceptionText;
-    throwJSExecutionException("%s", exceptionText.c_str());
+
+    Value jsStack = exObject.getProperty("stack");
+    if (jsStack.isNull() || !jsStack.isString()) {
+      throwJSExecutionException("%s", exceptionText.c_str());
+    } else {
+      LOG(ERROR) << "Got JS Stack: " << jsStack.toString().str();
+      throwJSExecutionExceptionWithStack(
+        exceptionText.c_str(), jsStack.toString().str().c_str());
+    }
   }
   return result;
 }
diff --git a/ReactCommon/cxxreact/JSCHelpers.h b/ReactCommon/cxxreact/JSCHelpers.h
index 57b03e31e..eb29058ef 100644
--- a/ReactCommon/cxxreact/JSCHelpers.h
+++ b/ReactCommon/cxxreact/JSCHelpers.h
@@ -17,12 +17,26 @@
 namespace facebook {
 namespace react {
 
-struct JsException : std::runtime_error {
-  using std::runtime_error::runtime_error;
+class JSException : public std::runtime_error {
+public:
+  explicit JSException(const char* msg)
+    : std::runtime_error(msg)
+    , stack_("") {}
+
+  JSException(const char* msg, const char* stack)
+    : std::runtime_error(msg)
+    , stack_(stack) {}
+
+  const std::string& getStack() const {
+    return stack_;
+  }
+
+private:
+  std::string stack_;
 };
 
 inline void throwJSExecutionException(const char* msg) {
-  throw JsException(msg);
+  throw JSException(msg);
 }
 
 template <typename... Args>
@@ -31,7 +45,12 @@ inline void throwJSExecutionException(const char* fmt, Args... args) {
   msgSize = std::min(512, msgSize + 1);
   char *msg = (char*) alloca(msgSize);
   snprintf(msg, msgSize, fmt, args...);
-  throw JsException(msg);
+  throw JSException(msg);
+}
+
+template <typename... Args>
+inline void throwJSExecutionExceptionWithStack(const char* msg, const char* stack) {
+  throw JSException(msg, stack);
 }
 
 void installGlobalFunction(