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Diffstat (limited to 'cros_utils/contextlib3.py')
| -rw-r--r-- | cros_utils/contextlib3.py | 116 |
1 files changed, 0 insertions, 116 deletions
diff --git a/cros_utils/contextlib3.py b/cros_utils/contextlib3.py deleted file mode 100644 index 9fabbf6e..00000000 --- a/cros_utils/contextlib3.py +++ /dev/null @@ -1,116 +0,0 @@ -# -*- coding: utf-8 -*- -# Copyright 2019 The Chromium OS Authors. All rights reserved. -# Use of this source code is governed by a BSD-style license that can be -# found in the LICENSE file. - -"""Random utilties from Python3's contextlib.""" - -from __future__ import division -from __future__ import print_function - -import sys - - -class ExitStack(object): - """https://docs.python.org/3/library/contextlib.html#contextlib.ExitStack""" - - def __init__(self): - self._stack = [] - self._is_entered = False - - def _assert_is_entered(self): - # Strictly, entering has no effect on the operations that call this. - # However, if you're trying to e.g. push things to an ExitStack that hasn't - # yet been entered, that's likely a bug. - assert self._is_entered, 'ExitStack op performed before entering' - - def __enter__(self): - self._is_entered = True - return self - - def _perform_exit(self, exc_type, exc, exc_traceback): - # I suppose a better name for this is - # `take_exception_handling_into_our_own_hands`, but that's harder to type. - exception_handled = False - while self._stack: - fn = self._stack.pop() - # The except clause below is meant to run as-if it's a `finally` block, - # but `finally` blocks don't have easy access to exceptions currently in - # flight. Hence, we do need to catch things like KeyboardInterrupt, - # SystemExit, ... - # pylint: disable=bare-except - try: - # If an __exit__ handler returns a truthy value, we should assume that - # it handled the exception appropriately. Otherwise, we need to keep it - # with us. (PEP 343) - if fn(exc_type, exc, exc_traceback): - exc_type, exc, exc_traceback = None, None, None - exception_handled = True - except: - # Python2 doesn't appear to have the notion of 'exception causes', - # which is super unfortunate. In the case: - # - # @contextlib.contextmanager - # def foo() - # try: - # yield - # finally: - # raise ValueError - # - # with foo(): - # assert False - # - # ...Python will only note the ValueError; nothing about the failing - # assertion is printed. - # - # I guess on the bright side, that means we don't have to fiddle with - # __cause__s/etc. - exc_type, exc, exc_traceback = sys.exc_info() - exception_handled = True - - if not exception_handled: - return False - - # Something changed. We either need to raise for ourselves, or note that - # the exception has been suppressed. - if exc_type is not None: - raise exc_type, exc, exc_traceback - - # Otherwise, the exception was suppressed. Go us! - return True - - def __exit__(self, exc_type, exc, exc_traceback): - return self._perform_exit(exc_type, exc, exc_traceback) - - def close(self): - """Unwinds the exit stack, unregistering all events""" - self._perform_exit(None, None, None) - - def enter_context(self, cm): - """Enters the given context manager, and registers it to be exited.""" - self._assert_is_entered() - - # The spec specifically notes that we should take __exit__ prior to calling - # __enter__. - exit_cleanup = cm.__exit__ - result = cm.__enter__() - self._stack.append(exit_cleanup) - return result - - # pylint complains about `exit` being redefined. `exit` is the documented - # name of this param, and renaming it would break portability if someone - # decided to `push(exit=foo)`, so just ignore the lint. - # pylint: disable=redefined-builtin - def push(self, exit): - """Like `enter_context`, but won't enter the value given.""" - self._assert_is_entered() - self._stack.append(exit.__exit__) - - def callback(self, callback, *args, **kwargs): - """Performs the given callback on exit""" - self._assert_is_entered() - - def fn(_exc_type, _exc, _exc_traceback): - callback(*args, **kwargs) - - self._stack.append(fn) |