CoroWrapper in debug mode has incorrect throw method signature
Bahus opened this issue · 7 comments
Hello!
When PYTHONASYNCIODEBUG is set asyncio wraps each coroutine in special CoroWrapperclass which has incorrect signature for throw method:
def throw(self, exc):
return self.gen.throw(exc)However it should be:
def throw(self, type, value=None, traceback=None):
return self.gen.throw(type, value, traceback)For example the problem appears when I'm using Tornado web-server with enabled asyncio debugging mode exception thrown in a coroutine causes another one:
Traceback (most recent call last):
File ".../lib/python3.5/site-packages/tornado/web.py", line 1445, in _execute
result = yield result
File ".../lib/python3.5/site-packages/tornado/gen.py", line 1008, in run
value = future.result()
File ".../lib/python3.5/site-packages/tornado/concurrent.py", line 232, in result
raise_exc_info(self._exc_info)
File "<string>", line 3, in raise_exc_info
File ".../lib/python3.5/site-packages/tornado/gen.py", line 1014, in run
yielded = self.gen.throw(*exc_info)
File "<string>", line 6, in _wrap_awaitable
TypeError: throw() takes 2 positional arguments but 4 were given
See tornado's code here.
Hi,
Indeed, it seems that CoroWrapper.throw should have the same signature than generator.throw():
https://docs.python.org/3/reference/expressions.html#generator.throw
However, the documentation doesn't say that it is possible to pass an exception instance if type is the only argument.
What about fix for this problem?
The change to fix this was committed a year ago, so Python 3.6 should have it fixed.
I use tornado like this:
tornado.platform.asyncio.AsyncIOMainLoop().install()
loop = asyncio.get_event_loop()
loop.set_debug(True)
tornado_app = app.webapp.TornadoApp()
tornado_app.listen(8080)
loop.run_forever()And any exception in tornado web request handler re-throws:
[E 170726 17:32:04 web:1590] Uncaught exception GET /r/1 (::1)
HTTPServerRequest(...)
Traceback (most recent call last):
File "/home/soar/virtualenvs/v1/lib/python3.5/site-packages/tornado/web.py", line 1511, in _execute
result = yield result
File "/home/soar/virtualenvs/v1/lib/python3.5/site-packages/tornado/gen.py", line 1055, in run
value = future.result()
File "/home/soar/virtualenvs/v1/lib/python3.5/site-packages/tornado/concurrent.py", line 238, in result
raise_exc_info(self._exc_info)
File "<string>", line 4, in raise_exc_info
File "/home/soar/virtualenvs/v1/lib/python3.5/site-packages/tornado/gen.py", line 1063, in run
yielded = self.gen.throw(*exc_info)
File "<string>", line 6, in _wrap_awaitable
TypeError: throw() takes 2 positional arguments but 4 were given
Without loop.set_debug() - I see original exception as expected.
What are the versions of Python and Tornado?