Make startup errors in the websocket executor invalidate the bridge

Reviewed By: mhorowitz

Differential Revision: D5226936

fbshipit-source-id: b6d605974674d0e6f86559f2583553e3636d389b

Libraries/WebSocket/RCTWebSocketExecutor.m

@@ -172,6 +172,11 @@ - (void)sendMessage:(NSDictionary<NSString *, id> *)message onReply:(RCTWSMessag
 
 - (void)executeApplicationScript:(NSData *)script sourceURL:(NSURL *)URL onComplete:(RCTJavaScriptCompleteBlock)onComplete
 {
+  // Hack: the bridge transitions out of loading state as soon as this method returns, which prevents us
+  // from completely invalidating the bridge and preventing an endless barage of RCTLog.logIfNoNativeHook
+  // calls if the JS execution environment is broken. We therefore block this thread until this message has returned.
+  dispatch_semaphore_t scriptSem = dispatch_semaphore_create(0);
+
   NSDictionary<NSString *, id> *message = @{
     @"method": @"executeApplicationScript",
     @"url": RCTNullIfNil(URL.absoluteString),
@@ -184,7 +189,10 @@ - (void)executeApplicationScript:(NSData *)script sourceURL:(NSURL *)URL onCompl
       NSString *error = reply[@"error"];
       onComplete(error ? RCTErrorWithMessage(error) : nil);
     }
+    dispatch_semaphore_signal(scriptSem);
   }];
+
+  dispatch_semaphore_wait(scriptSem, DISPATCH_TIME_FOREVER);
 }
 
 - (void)flushedQueue:(RCTJavaScriptCallback)onComplete

React/CxxBridge/RCTCxxBridge.mm

@@ -1010,7 +1010,11 @@ - (void)enqueueJSCall:(NSString *)module method:(NSString *)method args:(NSArray
       // ensureOnJavaScriptThread may execute immediately, so use jsMessageThread, to make sure
       // the block is invoked after callJSFunction
       if (completion) {
-        self->_jsMessageThread->runOnQueue(completion);
+        if (self->_jsMessageThread) {
+          self->_jsMessageThread->runOnQueue(completion);
+        } else {
+          RCTLogWarn(@"Can't invoke completion without messageThread");
+        }
       }
     }
   }];