Error handling for concrete JS executor

Reviewed By: adamjernst

Differential Revision: D3235189

fb-gh-sync-id: a6d545a6b0b388c52305e2936371776d579460cd
fbshipit-source-id: a6d545a6b0b388c52305e2936371776d579460cd

React/Executors/RCTJSCExecutor.h

@@ -25,6 +25,14 @@ RCT_EXTERN NSString *const RCTJSCThreadName;
  */
 RCT_EXTERN NSString *const RCTJavaScriptContextCreatedNotification;
 
+/**
+ * Create a NSError from a JSError object.
+ *
+ * If available, the error's userInfo property will contain the JS stacktrace under
+ * the RCTJSStackTraceKey key.
+ */
+RCT_EXTERN NSError *RCTNSErrorFromJSError(JSContextRef context, JSValueRef jsError);
+
 /**
  * Uses a JavaScriptCore context as the execution engine.
  */

React/Executors/RCTJSCExecutor.mm

@@ -144,7 +144,7 @@ static NSString *RCTJSValueToJSONString(JSContextRef context, JSValueRef value,
   return (__bridge_transfer NSString *)string;
 }
 
-static NSError *RCTNSErrorFromJSError(JSContextRef context, JSValueRef jsError)
+NSError *RCTNSErrorFromJSError(JSContextRef context, JSValueRef jsError)
 {
   NSMutableDictionary *errorInfo = [NSMutableDictionary new];