demandimport: fix a crash in LazyFinder.__delattr__
I was tinkering with `with hgdemandimport.deactivated()` wrapped around loading
the keyring module, and got spew that seemed to be confirmed by PyCharm. But I
can't believe we haven't seen this before (and phabricator uses the same
pattern):
** Unknown exception encountered with possibly-broken third-party extension "mercurial_keyring" 1.4.3 (keyring 23.11.0, backend unknown)
** which supports versions unknown of Mercurial.
** Please disable "mercurial_keyring" and try your action again.
** If that fixes the bug please report it to https://foss.heptapod.net/mercurial/mercurial_keyring/issues
** Python 3.9.15 (main, Oct 13 2022, 04:28:25) [GCC 7.5.0]
** Mercurial Distributed SCM (version 6.3.1)
** Extensions loaded: absorb, attorc
20220315, blackbox, eol, extdiff, fastannotate, lfs, mercurial_keyring 1.4.3 (keyring 23.11.0, backend unknown), phabblocker
20220315, phabricator
20220315, purge, rebase, schemes, share, show, strip, uncommit
Traceback (most recent call last):
File "/usr/local/bin/hg", line 59, in <module>
dispatch.run()
File "/usr/local/lib/python3.9/site-packages/mercurial/dispatch.py", line 143, in run
status = dispatch(req)
File "/usr/local/lib/python3.9/site-packages/mercurial/dispatch.py", line 232, in dispatch
status = _rundispatch(req)
File "/usr/local/lib/python3.9/site-packages/mercurial/dispatch.py", line 276, in _rundispatch
ret = _runcatch(req) or 0
File "/usr/local/lib/python3.9/site-packages/mercurial/dispatch.py", line 451, in _runcatch
return _callcatch(ui, _runcatchfunc)
File "/usr/local/lib/python3.9/site-packages/mercurial/dispatch.py", line 461, in _callcatch
return scmutil.callcatch(ui, func)
File "/usr/local/lib/python3.9/site-packages/mercurial/scmutil.py", line 153, in callcatch
return func()
File "/usr/local/lib/python3.9/site-packages/mercurial/dispatch.py", line 441, in _runcatchfunc
return _dispatch(req)
File "/usr/local/lib/python3.9/site-packages/mercurial/dispatch.py", line 1265, in _dispatch
return runcommand(
File "/usr/local/lib/python3.9/site-packages/mercurial/dispatch.py", line 899, in runcommand
ret = _runcommand(ui, options, cmd, d)
File "/usr/local/lib/python3.9/site-packages/mercurial/dispatch.py", line 1277, in _runcommand
return cmdfunc()
File "/usr/local/lib/python3.9/site-packages/mercurial/dispatch.py", line 1263, in <lambda>
d = lambda: util.checksignature(func)(ui, *args, **strcmdopt)
File "/usr/local/lib/python3.9/site-packages/mercurial/util.py", line 1880, in check
return func(*args, **kwargs)
File "/root/mercurial_keyring/mercurial_keyring/mercurial_keyring.py", line 962, in cmd_keyring_check
user, pwd, source, final_url = handler.get_credentials(
File "/root/mercurial_keyring/mercurial_keyring/mercurial_keyring.py", line 497, in get_credentials
keyring_pwd = password_store.get_http_password(keyring_url, actual_user)
File "/root/mercurial_keyring/mercurial_keyring/mercurial_keyring.py", line 287, in get_http_password
return self._read_password_from_keyring(
File "/root/mercurial_keyring/mercurial_keyring/mercurial_keyring.py", line 335, in _read_password_from_keyring
keyring = import_keyring()
>> `with hgdemandimport.deactivated()` inserted here
File "/root/mercurial_keyring/mercurial_keyring/mercurial_keyring.py", line 120, in import_keyring
return _import_keyring()
File "/root/mercurial_keyring/mercurial_keyring/mercurial_keyring.py", line 133, in _import_keyring
mod, was_imported_now = meu.direct_import_ext(
File "/usr/lib/python3.9/site-packages/mercurial_extension_utils.py", line 1381, in direct_import_ext
__import__(module_name)
File "<frozen importlib._bootstrap>", line 1007, in _find_and_load
File "<frozen importlib._bootstrap>", line 986, in _find_and_load_unlocked
File "<frozen importlib._bootstrap>", line 680, in _load_unlocked
File "/usr/local/lib/python3.9/site-packages/hgdemandimport/demandimportpy3.py", line 46, in exec_module
self.loader.exec_module(module)
File "/usr/lib/python3.9/site-packages/keyring/__init__.py", line 1, in <module>
from .core import (
File "<frozen importlib._bootstrap>", line 1007, in _find_and_load
File "<frozen importlib._bootstrap>", line 986, in _find_and_load_unlocked
File "<frozen importlib._bootstrap>", line 680, in _load_unlocked
File "/usr/local/lib/python3.9/site-packages/hgdemandimport/demandimportpy3.py", line 46, in exec_module
self.loader.exec_module(module)
File "/usr/lib/python3.9/site-packages/keyring/core.py", line 11, in <module>
from . import backend, credentials
File "<frozen importlib._bootstrap>", line 1007, in _find_and_load
File "<frozen importlib._bootstrap>", line 986, in _find_and_load_unlocked
File "<frozen importlib._bootstrap>", line 680, in _load_unlocked
File "/usr/local/lib/python3.9/site-packages/hgdemandimport/demandimportpy3.py", line 46, in exec_module
self.loader.exec_module(module)
File "/usr/lib/python3.9/site-packages/keyring/backend.py", line 13, in <module>
from .py312compat import metadata
File "<frozen importlib._bootstrap>", line 1007, in _find_and_load
File "<frozen importlib._bootstrap>", line 986, in _find_and_load_unlocked
File "<frozen importlib._bootstrap>", line 680, in _load_unlocked
File "/usr/local/lib/python3.9/site-packages/hgdemandimport/demandimportpy3.py", line 46, in exec_module
self.loader.exec_module(module)
File "/usr/lib/python3.9/site-packages/keyring/py312compat.py", line 10, in <module>
import importlib_metadata as metadata # type: ignore
File "<frozen importlib._bootstrap>", line 1007, in _find_and_load
File "<frozen importlib._bootstrap>", line 986, in _find_and_load_unlocked
File "<frozen importlib._bootstrap>", line 680, in _load_unlocked
File "/usr/local/lib/python3.9/site-packages/hgdemandimport/demandimportpy3.py", line 46, in exec_module
self.loader.exec_module(module)
File "/usr/lib/python3.9/site-packages/importlib_metadata/__init__.py", line 715, in <module>
class MetadataPathFinder(NullFinder, DistributionFinder):
File "/usr/lib/python3.9/site-packages/importlib_metadata/_compat.py", line 24, in install
disable_stdlib_finder()
File "/usr/lib/python3.9/site-packages/importlib_metadata/_compat.py", line 43, in disable_stdlib_finder
del finder.find_distributions
File "/usr/local/lib/python3.9/site-packages/hgdemandimport/demandimportpy3.py", line 88, in __delattr__
return delattr(object.__getattribute__(self, "_finder"))
TypeError: delattr expected 2 arguments, got 1
# demandimportpy3 - global demand-loading of modules for Mercurial
#
# Copyright 2017 Facebook Inc.
#
# This software may be used and distributed according to the terms of the
# GNU General Public License version 2 or any later version.
"""Lazy loading for Python 3.6 and above.
This uses the new importlib finder/loader functionality available in Python 3.5
and up. The code reuses most of the mechanics implemented inside importlib.util,
but with a few additions:
* Allow excluding certain modules from lazy imports.
* Expose an interface that's substantially the same as demandimport for
Python 2.
This also has some limitations compared to the Python 2 implementation:
* Much of the logic is per-package, not per-module, so any packages loaded
before demandimport is enabled will not be lazily imported in the future. In
practice, we only expect builtins to be loaded before demandimport is
enabled.
"""
# This line is unnecessary, but it satisfies test-check-py3-compat.t.
import contextlib
import importlib.util
import sys
from . import tracing
_deactivated = False
class _lazyloaderex(importlib.util.LazyLoader):
"""This is a LazyLoader except it also follows the _deactivated global and
the ignore list.
"""
def exec_module(self, module):
"""Make the module load lazily."""
with tracing.log('demandimport %s', module):
if _deactivated or module.__name__ in ignores:
self.loader.exec_module(module)
else:
super().exec_module(module)
class LazyFinder:
"""A wrapper around a ``MetaPathFinder`` that makes loaders lazy.
``sys.meta_path`` finders have their ``find_spec()`` called to locate a
module. This returns a ``ModuleSpec`` if found or ``None``. The
``ModuleSpec`` has a ``loader`` attribute, which is called to actually
load a module.
Our class wraps an existing finder and overloads its ``find_spec()`` to
replace the ``loader`` with our lazy loader proxy.
We have to use __getattribute__ to proxy the instance because some meta
path finders don't support monkeypatching.
"""
__slots__ = ("_finder",)
def __init__(self, finder):
object.__setattr__(self, "_finder", finder)
def __repr__(self):
return "<LazyFinder for %r>" % object.__getattribute__(self, "_finder")
# __bool__ is canonical Python 3. But check-code insists on __nonzero__ being
# defined via `def`.
def __nonzero__(self):
return bool(object.__getattribute__(self, "_finder"))
__bool__ = __nonzero__
def __getattribute__(self, name):
if name in ("_finder", "find_spec"):
return object.__getattribute__(self, name)
return getattr(object.__getattribute__(self, "_finder"), name)
def __delattr__(self, name):
return delattr(object.__getattribute__(self, "_finder"), name)
def __setattr__(self, name, value):
return setattr(object.__getattribute__(self, "_finder"), name, value)
def find_spec(self, fullname, path, target=None):
finder = object.__getattribute__(self, "_finder")
try:
find_spec = finder.find_spec
except AttributeError:
loader = finder.find_module(fullname, path)
if loader is None:
spec = None
else:
spec = importlib.util.spec_from_loader(fullname, loader)
else:
spec = find_spec(fullname, path, target)
# Lazy loader requires exec_module().
if (
spec is not None
and spec.loader is not None
and getattr(spec.loader, "exec_module", None)
):
spec.loader = _lazyloaderex(spec.loader)
return spec
ignores = set()
def init(ignoreset):
global ignores
ignores = ignoreset
def isenabled():
return not _deactivated and any(
isinstance(finder, LazyFinder) for finder in sys.meta_path
)
def disable():
new_finders = []
for finder in sys.meta_path:
new_finders.append(
finder._finder if isinstance(finder, LazyFinder) else finder
)
sys.meta_path[:] = new_finders
def enable():
new_finders = []
for finder in sys.meta_path:
new_finders.append(
LazyFinder(finder) if not isinstance(finder, LazyFinder) else finder
)
sys.meta_path[:] = new_finders
@contextlib.contextmanager
def deactivated():
# This implementation is a bit different from Python 2's. Python 3
# maintains a per-package finder cache in sys.path_importer_cache (see
# PEP 302). This means that we can't just call disable + enable.
# If we do that, in situations like:
#
# demandimport.enable()
# ...
# from foo.bar import mod1
# with demandimport.deactivated():
# from foo.bar import mod2
#
# mod2 will be imported lazily. (The converse also holds -- whatever finder
# first gets cached will be used.)
#
# Instead, have a global flag the LazyLoader can use.
global _deactivated
demandenabled = isenabled()
if demandenabled:
_deactivated = True
try:
yield
finally:
if demandenabled:
_deactivated = False