Fix error handling for nested exceptions

Reviewed By: mhorowitz

Differential Revision: D4551110

fbshipit-source-id: e593c1ef0dea27e95a387bcde6250aeb22d2e9cc

React/CxxModule/RCTCxxUtils.h

@@ -17,3 +17,10 @@ id RCTConvertFollyDynamic(const folly::dynamic &dyn);
 + (folly::dynamic)folly_dynamic:(id)json;
 
 @end
+
+namespace facebook {
+namespace react {
+
+NSError *tryAndReturnError(const std::function<void()>& func);
+
+} }

React/CxxModule/RCTCxxUtils.mm

@@ -10,7 +10,11 @@
 #import "RCTCxxUtils.h"
 
 #import <React/RCTFollyConvert.h>
+#import <React/RCTUtils.h>
 
+#include <jschelpers/Value.h>
+
+using namespace facebook::react;
 using namespace react::CxxUtils;
 
 id RCTConvertFollyDynamic(const folly::dynamic &dyn) {
@@ -33,3 +37,58 @@ id RCTConvertFollyDynamic(const folly::dynamic &dyn) {
 }
 
 @end
+
+namespace facebook {
+namespace react {
+
+static NSError *errorWithException(const std::exception& e)
+{
+  NSString *msg = @(e.what());
+  NSMutableDictionary *errorInfo = [NSMutableDictionary dictionary];
+
+  const JSException *jsException = dynamic_cast<const JSException*>(&e);
+  if (jsException) {
+    errorInfo[RCTJSRawStackTraceKey] = @(jsException->getStack().c_str());
+    msg = [@"Unhandled JS Exception: " stringByAppendingString:msg];
+  }
+
+  NSError *nestedError;
+  try {
+    std::rethrow_if_nested(e);
+  } catch(const std::exception& e) {
+    nestedError = errorWithException(e);
+  } catch(...) {}
+
+  if (nestedError) {
+    msg = [NSString stringWithFormat:@"%@\n\n%@", msg, [nestedError localizedDescription]];
+  }
+
+  errorInfo[NSLocalizedDescriptionKey] = msg;
+  return [NSError errorWithDomain:RCTErrorDomain code:1 userInfo:errorInfo];
+}
+
+NSError *tryAndReturnError(const std::function<void()>& func) {
+  try {
+    @try {
+      func();
+      return nil;
+    }
+    @catch (NSException *exception) {
+      NSString *message =
+      [NSString stringWithFormat:@"Exception '%@' was thrown from JS thread", exception];
+      return RCTErrorWithMessage(message);
+    }
+    @catch (id exception) {
+      // This will catch any other ObjC exception, but no C++ exceptions
+      return RCTErrorWithMessage(@"non-std ObjC Exception");
+    }
+  } catch (const std::exception &ex) {
+    return errorWithException(ex);
+  } catch (...) {
+    // On a 64-bit platform, this would catch ObjC exceptions, too, but not on
+    // 32-bit platforms, so we catch those with id exceptions above.
+    return RCTErrorWithMessage(@"non-std C++ exception");
+  }
+}
+
+} }