bpo-32528: Make asyncio.CancelledError a BaseException. (GH-13528)
This will address the common mistake many asyncio users make:
an "except Exception" clause breaking Tasks cancellation.
In addition to this change, we stop inheriting asyncio.TimeoutError
and asyncio.InvalidStateError from their concurrent.futures.*
counterparts. There's no point for these exceptions to share the
inheritance chain.
In 3.9 we'll focus on implementing supervisors and cancel scopes,
which should allow better handling of all exceptions, including
SystemExit and KeyboardInterrupt
diff --git a/Lib/asyncio/base_events.py b/Lib/asyncio/base_events.py
index de9fa4f..63b072b 100644
--- a/Lib/asyncio/base_events.py
+++ b/Lib/asyncio/base_events.py
@@ -186,7 +186,7 @@
def _run_until_complete_cb(fut):
if not fut.cancelled():
exc = fut.exception()
- if isinstance(exc, BaseException) and not isinstance(exc, Exception):
+ if isinstance(exc, (SystemExit, KeyboardInterrupt)):
# Issue #22429: run_forever() already finished, no need to
# stop it.
return
@@ -1196,7 +1196,7 @@
try:
await waiter
- except Exception:
+ except BaseException:
transport.close()
conmade_cb.cancel()
resume_cb.cancel()
@@ -1710,7 +1710,9 @@
if self._exception_handler is None:
try:
self.default_exception_handler(context)
- except Exception:
+ except (SystemExit, KeyboardInterrupt):
+ raise
+ except BaseException:
# Second protection layer for unexpected errors
# in the default implementation, as well as for subclassed
# event loops with overloaded "default_exception_handler".
@@ -1719,7 +1721,9 @@
else:
try:
self._exception_handler(self, context)
- except Exception as exc:
+ except (SystemExit, KeyboardInterrupt):
+ raise
+ except BaseException as exc:
# Exception in the user set custom exception handler.
try:
# Let's try default handler.
@@ -1728,7 +1732,9 @@
'exception': exc,
'context': context,
})
- except Exception:
+ except (SystemExit, KeyboardInterrupt):
+ raise
+ except BaseException:
# Guard 'default_exception_handler' in case it is
# overloaded.
logger.error('Exception in default exception handler '
diff --git a/Lib/asyncio/base_subprocess.py b/Lib/asyncio/base_subprocess.py
index f503f78..14d5051 100644
--- a/Lib/asyncio/base_subprocess.py
+++ b/Lib/asyncio/base_subprocess.py
@@ -182,7 +182,9 @@
for callback, data in self._pending_calls:
loop.call_soon(callback, *data)
self._pending_calls = None
- except Exception as exc:
+ except (SystemExit, KeyboardInterrupt):
+ raise
+ except BaseException as exc:
if waiter is not None and not waiter.cancelled():
waiter.set_exception(exc)
else:
diff --git a/Lib/asyncio/events.py b/Lib/asyncio/events.py
index 9a92351..d381b1c 100644
--- a/Lib/asyncio/events.py
+++ b/Lib/asyncio/events.py
@@ -79,7 +79,9 @@
def _run(self):
try:
self._context.run(self._callback, *self._args)
- except Exception as exc:
+ except (SystemExit, KeyboardInterrupt):
+ raise
+ except BaseException as exc:
cb = format_helpers._format_callback_source(
self._callback, self._args)
msg = f'Exception in callback {cb}'
diff --git a/Lib/asyncio/exceptions.py b/Lib/asyncio/exceptions.py
index cac31a5..e03602e 100644
--- a/Lib/asyncio/exceptions.py
+++ b/Lib/asyncio/exceptions.py
@@ -5,19 +5,16 @@
'IncompleteReadError', 'LimitOverrunError',
'SendfileNotAvailableError')
-import concurrent.futures
-from . import base_futures
-
-class CancelledError(concurrent.futures.CancelledError):
+class CancelledError(BaseException):
"""The Future or Task was cancelled."""
-class TimeoutError(concurrent.futures.TimeoutError):
+class TimeoutError(Exception):
"""The operation exceeded the given deadline."""
-class InvalidStateError(concurrent.futures.InvalidStateError):
+class InvalidStateError(Exception):
"""The operation is not allowed in this state."""
diff --git a/Lib/asyncio/proactor_events.py b/Lib/asyncio/proactor_events.py
index a849be1..7dfe295 100644
--- a/Lib/asyncio/proactor_events.py
+++ b/Lib/asyncio/proactor_events.py
@@ -212,7 +212,9 @@
try:
keep_open = self._protocol.eof_received()
- except Exception as exc:
+ except (SystemExit, KeyboardInterrupt):
+ raise
+ except BaseException as exc:
self._fatal_error(
exc, 'Fatal error: protocol.eof_received() call failed.')
return
@@ -235,7 +237,9 @@
if isinstance(self._protocol, protocols.BufferedProtocol):
try:
protocols._feed_data_to_buffered_proto(self._protocol, data)
- except Exception as exc:
+ except (SystemExit, KeyboardInterrupt):
+ raise
+ except BaseException as exc:
self._fatal_error(exc,
'Fatal error: protocol.buffer_updated() '
'call failed.')
@@ -625,7 +629,9 @@
except exceptions.CancelledError:
# _close_self_pipe() has been called, stop waiting for data
return
- except Exception as exc:
+ except (SystemExit, KeyboardInterrupt):
+ raise
+ except BaseException as exc:
self.call_exception_handler({
'message': 'Error on reading from the event loop self pipe',
'exception': exc,
diff --git a/Lib/asyncio/selector_events.py b/Lib/asyncio/selector_events.py
index 6461d30..f5f43a9 100644
--- a/Lib/asyncio/selector_events.py
+++ b/Lib/asyncio/selector_events.py
@@ -208,12 +208,14 @@
try:
await waiter
- except:
+ except BaseException:
transport.close()
raise
+ # It's now up to the protocol to handle the connection.
- # It's now up to the protocol to handle the connection.
- except Exception as exc:
+ except (SystemExit, KeyboardInterrupt):
+ raise
+ except BaseException as exc:
if self._debug:
context = {
'message':
@@ -370,7 +372,9 @@
data = sock.recv(n)
except (BlockingIOError, InterruptedError):
return # try again next time
- except Exception as exc:
+ except (SystemExit, KeyboardInterrupt):
+ raise
+ except BaseException as exc:
fut.set_exception(exc)
else:
fut.set_result(data)
@@ -404,7 +408,9 @@
nbytes = sock.recv_into(buf)
except (BlockingIOError, InterruptedError):
return # try again next time
- except Exception as exc:
+ except (SystemExit, KeyboardInterrupt):
+ raise
+ except BaseException as exc:
fut.set_exception(exc)
else:
fut.set_result(nbytes)
@@ -447,7 +453,9 @@
n = sock.send(view[start:])
except (BlockingIOError, InterruptedError):
return
- except Exception as exc:
+ except (SystemExit, KeyboardInterrupt):
+ raise
+ except BaseException as exc:
fut.set_exception(exc)
return
@@ -487,7 +495,9 @@
fut.add_done_callback(
functools.partial(self._sock_write_done, fd))
self.add_writer(fd, self._sock_connect_cb, fut, sock, address)
- except Exception as exc:
+ except (SystemExit, KeyboardInterrupt):
+ raise
+ except BaseException as exc:
fut.set_exception(exc)
else:
fut.set_result(None)
@@ -507,7 +517,9 @@
except (BlockingIOError, InterruptedError):
# socket is still registered, the callback will be retried later
pass
- except Exception as exc:
+ except (SystemExit, KeyboardInterrupt):
+ raise
+ except BaseException as exc:
fut.set_exception(exc)
else:
fut.set_result(None)
@@ -537,7 +549,9 @@
conn.setblocking(False)
except (BlockingIOError, InterruptedError):
self.add_reader(fd, self._sock_accept, fut, True, sock)
- except Exception as exc:
+ except (SystemExit, KeyboardInterrupt):
+ raise
+ except BaseException as exc:
fut.set_exception(exc)
else:
fut.set_result((conn, address))
@@ -785,7 +799,9 @@
buf = self._protocol.get_buffer(-1)
if not len(buf):
raise RuntimeError('get_buffer() returned an empty buffer')
- except Exception as exc:
+ except (SystemExit, KeyboardInterrupt):
+ raise
+ except BaseException as exc:
self._fatal_error(
exc, 'Fatal error: protocol.get_buffer() call failed.')
return
@@ -794,7 +810,9 @@
nbytes = self._sock.recv_into(buf)
except (BlockingIOError, InterruptedError):
return
- except Exception as exc:
+ except (SystemExit, KeyboardInterrupt):
+ raise
+ except BaseException as exc:
self._fatal_error(exc, 'Fatal read error on socket transport')
return
@@ -804,7 +822,9 @@
try:
self._protocol.buffer_updated(nbytes)
- except Exception as exc:
+ except (SystemExit, KeyboardInterrupt):
+ raise
+ except BaseException as exc:
self._fatal_error(
exc, 'Fatal error: protocol.buffer_updated() call failed.')
@@ -815,7 +835,9 @@
data = self._sock.recv(self.max_size)
except (BlockingIOError, InterruptedError):
return
- except Exception as exc:
+ except (SystemExit, KeyboardInterrupt):
+ raise
+ except BaseException as exc:
self._fatal_error(exc, 'Fatal read error on socket transport')
return
@@ -825,7 +847,9 @@
try:
self._protocol.data_received(data)
- except Exception as exc:
+ except (SystemExit, KeyboardInterrupt):
+ raise
+ except BaseException as exc:
self._fatal_error(
exc, 'Fatal error: protocol.data_received() call failed.')
@@ -835,7 +859,9 @@
try:
keep_open = self._protocol.eof_received()
- except Exception as exc:
+ except (SystemExit, KeyboardInterrupt):
+ raise
+ except BaseException as exc:
self._fatal_error(
exc, 'Fatal error: protocol.eof_received() call failed.')
return
@@ -871,7 +897,9 @@
n = self._sock.send(data)
except (BlockingIOError, InterruptedError):
pass
- except Exception as exc:
+ except (SystemExit, KeyboardInterrupt):
+ raise
+ except BaseException as exc:
self._fatal_error(exc, 'Fatal write error on socket transport')
return
else:
@@ -894,7 +922,9 @@
n = self._sock.send(self._buffer)
except (BlockingIOError, InterruptedError):
pass
- except Exception as exc:
+ except (SystemExit, KeyboardInterrupt):
+ raise
+ except BaseException as exc:
self._loop._remove_writer(self._sock_fd)
self._buffer.clear()
self._fatal_error(exc, 'Fatal write error on socket transport')
@@ -970,7 +1000,9 @@
pass
except OSError as exc:
self._protocol.error_received(exc)
- except Exception as exc:
+ except (SystemExit, KeyboardInterrupt):
+ raise
+ except BaseException as exc:
self._fatal_error(exc, 'Fatal read error on datagram transport')
else:
self._protocol.datagram_received(data, addr)
@@ -1007,7 +1039,9 @@
except OSError as exc:
self._protocol.error_received(exc)
return
- except Exception as exc:
+ except (SystemExit, KeyboardInterrupt):
+ raise
+ except BaseException as exc:
self._fatal_error(
exc, 'Fatal write error on datagram transport')
return
@@ -1030,7 +1064,9 @@
except OSError as exc:
self._protocol.error_received(exc)
return
- except Exception as exc:
+ except (SystemExit, KeyboardInterrupt):
+ raise
+ except BaseException as exc:
self._fatal_error(
exc, 'Fatal write error on datagram transport')
return
diff --git a/Lib/asyncio/sslproto.py b/Lib/asyncio/sslproto.py
index 97a6fc6..8546985 100644
--- a/Lib/asyncio/sslproto.py
+++ b/Lib/asyncio/sslproto.py
@@ -527,7 +527,9 @@
try:
ssldata, appdata = self._sslpipe.feed_ssldata(data)
- except Exception as e:
+ except (SystemExit, KeyboardInterrupt):
+ raise
+ except BaseException as e:
self._fatal_error(e, 'SSL error in data received')
return
@@ -542,7 +544,9 @@
self._app_protocol, chunk)
else:
self._app_protocol.data_received(chunk)
- except Exception as ex:
+ except (SystemExit, KeyboardInterrupt):
+ raise
+ except BaseException as ex:
self._fatal_error(
ex, 'application protocol failed to receive SSL data')
return
@@ -628,7 +632,9 @@
raise handshake_exc
peercert = sslobj.getpeercert()
- except Exception as exc:
+ except (SystemExit, KeyboardInterrupt):
+ raise
+ except BaseException as exc:
if isinstance(exc, ssl.CertificateError):
msg = 'SSL handshake failed on verifying the certificate'
else:
@@ -691,7 +697,9 @@
# delete it and reduce the outstanding buffer size.
del self._write_backlog[0]
self._write_buffer_size -= len(data)
- except Exception as exc:
+ except (SystemExit, KeyboardInterrupt):
+ raise
+ except BaseException as exc:
if self._in_handshake:
# Exceptions will be re-raised in _on_handshake_complete.
self._on_handshake_complete(exc)
diff --git a/Lib/asyncio/staggered.py b/Lib/asyncio/staggered.py
index feec681..27c665a 100644
--- a/Lib/asyncio/staggered.py
+++ b/Lib/asyncio/staggered.py
@@ -105,7 +105,9 @@
try:
result = await coro_fn()
- except Exception as e:
+ except (SystemExit, KeyboardInterrupt):
+ raise
+ except BaseException as e:
exceptions[this_index] = e
this_failed.set() # Kickstart the next coroutine
else:
diff --git a/Lib/asyncio/tasks.py b/Lib/asyncio/tasks.py
index 1dc5952..78e7600 100644
--- a/Lib/asyncio/tasks.py
+++ b/Lib/asyncio/tasks.py
@@ -260,11 +260,11 @@
super().set_result(exc.value)
except exceptions.CancelledError:
super().cancel() # I.e., Future.cancel(self).
- except Exception as exc:
- super().set_exception(exc)
- except BaseException as exc:
+ except (KeyboardInterrupt, SystemExit) as exc:
super().set_exception(exc)
raise
+ except BaseException as exc:
+ super().set_exception(exc)
else:
blocking = getattr(result, '_asyncio_future_blocking', None)
if blocking is not None:
@@ -318,7 +318,7 @@
def __wakeup(self, future):
try:
future.result()
- except Exception as exc:
+ except BaseException as exc:
# This may also be a cancellation.
self.__step(exc)
else:
@@ -858,7 +858,9 @@
def callback():
try:
futures._chain_future(ensure_future(coro, loop=loop), future)
- except Exception as exc:
+ except (SystemExit, KeyboardInterrupt):
+ raise
+ except BaseException as exc:
if future.set_running_or_notify_cancel():
future.set_exception(exc)
raise
diff --git a/Lib/asyncio/transports.py b/Lib/asyncio/transports.py
index 233bbb5..47b37fa 100644
--- a/Lib/asyncio/transports.py
+++ b/Lib/asyncio/transports.py
@@ -262,7 +262,9 @@
self._protocol_paused = True
try:
self._protocol.pause_writing()
- except Exception as exc:
+ except (SystemExit, KeyboardInterrupt):
+ raise
+ except BaseException as exc:
self._loop.call_exception_handler({
'message': 'protocol.pause_writing() failed',
'exception': exc,
@@ -276,7 +278,9 @@
self._protocol_paused = False
try:
self._protocol.resume_writing()
- except Exception as exc:
+ except (SystemExit, KeyboardInterrupt):
+ raise
+ except BaseException as exc:
self._loop.call_exception_handler({
'message': 'protocol.resume_writing() failed',
'exception': exc,
diff --git a/Lib/asyncio/unix_events.py b/Lib/asyncio/unix_events.py
index 1aa3b39..81d10b1 100644
--- a/Lib/asyncio/unix_events.py
+++ b/Lib/asyncio/unix_events.py
@@ -194,7 +194,9 @@
self._child_watcher_callback, transp)
try:
await waiter
- except Exception:
+ except (SystemExit, KeyboardInterrupt):
+ raise
+ except BaseException:
transp.close()
await transp._wait()
raise
@@ -390,7 +392,9 @@
else:
self._sock_sendfile_update_filepos(fileno, offset, total_sent)
fut.set_exception(exc)
- except Exception as exc:
+ except (SystemExit, KeyboardInterrupt):
+ raise
+ except BaseException as exc:
self._sock_sendfile_update_filepos(fileno, offset, total_sent)
fut.set_exception(exc)
else:
@@ -641,7 +645,9 @@
n = os.write(self._fileno, data)
except (BlockingIOError, InterruptedError):
n = 0
- except Exception as exc:
+ except (SystemExit, KeyboardInterrupt):
+ raise
+ except BaseException as exc:
self._conn_lost += 1
self._fatal_error(exc, 'Fatal write error on pipe transport')
return
@@ -661,7 +667,9 @@
n = os.write(self._fileno, self._buffer)
except (BlockingIOError, InterruptedError):
pass
- except Exception as exc:
+ except (SystemExit, KeyboardInterrupt):
+ raise
+ except BaseException as exc:
self._buffer.clear()
self._conn_lost += 1
# Remove writer here, _fatal_error() doesn't it
@@ -879,7 +887,9 @@
def _sig_chld(self):
try:
self._do_waitpid_all()
- except Exception as exc:
+ except (SystemExit, KeyboardInterrupt):
+ raise
+ except BaseException as exc:
# self._loop should always be available here
# as '_sig_chld' is added as a signal handler
# in 'attach_loop'
diff --git a/Lib/asyncio/windows_events.py b/Lib/asyncio/windows_events.py
index 29750f1..b5b2e24 100644
--- a/Lib/asyncio/windows_events.py
+++ b/Lib/asyncio/windows_events.py
@@ -388,7 +388,9 @@
**kwargs)
try:
await waiter
- except Exception:
+ except (SystemExit, KeyboardInterrupt):
+ raise
+ except BaseException:
transp.close()
await transp._wait()
raise