diff options
| -rw-r--r-- | Lib/asyncio/base_futures.py | 25 | ||||
| -rw-r--r-- | Lib/test/test_asyncio/test_futures2.py | 18 | ||||
| -rw-r--r-- | Misc/NEWS.d/next/Library/2020-10-29-11-17-35.bpo-42183.50ZcIi.rst | 4 |
3 files changed, 44 insertions, 3 deletions
diff --git a/Lib/asyncio/base_futures.py b/Lib/asyncio/base_futures.py index 22f2980..2c01ac9 100644 --- a/Lib/asyncio/base_futures.py +++ b/Lib/asyncio/base_futures.py @@ -1,6 +1,7 @@ __all__ = () import reprlib +from _thread import get_ident from . import format_helpers @@ -41,6 +42,16 @@ def _format_callbacks(cb): return f'cb=[{cb}]' +# bpo-42183: _repr_running is needed for repr protection +# when a Future or Task result contains itself directly or indirectly. +# The logic is borrowed from @reprlib.recursive_repr decorator. +# Unfortunately, the direct decorator usage is impossible because of +# AttributeError: '_asyncio.Task' object has no attribute '__module__' error. +# +# After fixing this thing we can return to the decorator based approach. +_repr_running = set() + + def _future_repr_info(future): # (Future) -> str """helper function for Future.__repr__""" @@ -49,9 +60,17 @@ def _future_repr_info(future): if future._exception is not None: info.append(f'exception={future._exception!r}') else: - # use reprlib to limit the length of the output, especially - # for very long strings - result = reprlib.repr(future._result) + key = id(future), get_ident() + if key in _repr_running: + result = '...' + else: + _repr_running.add(key) + try: + # use reprlib to limit the length of the output, especially + # for very long strings + result = reprlib.repr(future._result) + finally: + _repr_running.discard(key) info.append(f'result={result}') if future._callbacks: info.append(_format_callbacks(future._callbacks)) diff --git a/Lib/test/test_asyncio/test_futures2.py b/Lib/test/test_asyncio/test_futures2.py new file mode 100644 index 0000000..13dbc70 --- /dev/null +++ b/Lib/test/test_asyncio/test_futures2.py @@ -0,0 +1,18 @@ +# IsolatedAsyncioTestCase based tests +import asyncio +import unittest + + +class FutureTests(unittest.IsolatedAsyncioTestCase): + async def test_recursive_repr_for_pending_tasks(self): + # The call crashes if the guard for recursive call + # in base_futures:_future_repr_info is absent + # See Also: https://bugs.python.org/issue42183 + + async def func(): + return asyncio.all_tasks() + + # The repr() call should not raise RecursiveError at first. + # The check for returned string is not very reliable but + # exact comparison for the whole string is even weaker. + self.assertIn('...', repr(await asyncio.wait_for(func(), timeout=10))) diff --git a/Misc/NEWS.d/next/Library/2020-10-29-11-17-35.bpo-42183.50ZcIi.rst b/Misc/NEWS.d/next/Library/2020-10-29-11-17-35.bpo-42183.50ZcIi.rst new file mode 100644 index 0000000..f6d7653 --- /dev/null +++ b/Misc/NEWS.d/next/Library/2020-10-29-11-17-35.bpo-42183.50ZcIi.rst @@ -0,0 +1,4 @@ +Fix a stack overflow error for asyncio Task or Future repr(). + +The overflow occurs under some circumstances when a Task or Future +recursively returns itself. |