Catch and log all errors that occur in event handlers

src/engineio/asyncio_server.py

@@ -469,13 +469,10 @@ async def _trigger_event(self, event, *args, **kwargs):
         run_async = kwargs.pop('run_async', False)
         ret = None
         if event in self.handlers:
-            if asyncio.iscoroutinefunction(self.handlers[event]) is True:
-                if run_async:
-                    return self.start_background_task(self.handlers[event],
-                                                      *args)
-                else:
+            if asyncio.iscoroutinefunction(self.handlers[event]):
+                async def run_async_handler():
                     try:
-                        ret = await self.handlers[event](*args)
+                        return await self.handlers[event](*args)
                     except asyncio.CancelledError:  # pragma: no cover
                         pass
                     except:
@@ -484,21 +481,26 @@ async def _trigger_event(self, event, *args, **kwargs):
                             # if connect handler raised error we reject the
                             # connection
                             return False
-            else:
-                if run_async:
-                    async def async_handler():
-                        return self.handlers[event](*args)
 
-                    return self.start_background_task(async_handler)
+                if run_async:
+                    ret = self.start_background_task(run_async_handler)
                 else:
+                    ret = await run_async_handler()
+            else:
+                async def run_sync_handler():
                     try:
-                        ret = self.handlers[event](*args)
+                        return self.handlers[event](*args)
                     except:
                         self.logger.exception(event + ' handler error')
                         if event == 'connect':
                             # if connect handler raised error we reject the
                             # connection
                             return False
+
+                if run_async:
+                    ret = self.start_background_task(run_sync_handler)
+                else:
+                    ret = await run_sync_handler()
         return ret
 
     async def _service_task(self):  # pragma: no cover

src/engineio/server.py

@@ -637,9 +637,7 @@ def _trigger_event(self, event, *args, **kwargs):
         """Invoke an event handler."""
         run_async = kwargs.pop('run_async', False)
         if event in self.handlers:
-            if run_async:
-                return self.start_background_task(self.handlers[event], *args)
-            else:
+            def run_handler():
                 try:
                     return self.handlers[event](*args)
                 except:
@@ -649,6 +647,11 @@ def _trigger_event(self, event, *args, **kwargs):
                         # connection
                         return False
 
+            if run_async:
+                return self.start_background_task(run_handler)
+            else:
+                return run_handler()
+
     def _get_socket(self, sid):
         """Return the socket object for a given session."""
         try:

tests/asyncio/test_asyncio_server.py

@@ -1103,8 +1103,7 @@ def foo_handler(arg):
         s = asyncio_server.AsyncServer()
         s.on('message', handler=foo_handler)
         fut = _run(s._trigger_event('message', 'bar', run_async=True))
-        with pytest.raises(ZeroDivisionError):
-            asyncio.get_event_loop().run_until_complete(fut)
+        asyncio.get_event_loop().run_until_complete(fut)
         assert result == ['bar']
 
     def test_trigger_event_coroutine_async_error(self):
@@ -1117,8 +1116,7 @@ async def foo_handler(arg):
         s = asyncio_server.AsyncServer()
         s.on('message', handler=foo_handler)
         fut = _run(s._trigger_event('message', 'bar', run_async=True))
-        with pytest.raises(ZeroDivisionError):
-            asyncio.get_event_loop().run_until_complete(fut)
+        asyncio.get_event_loop().run_until_complete(fut)
         assert result == ['bar']
 
     def test_create_queue(self):