Mercurial > hg
view mercurial/policy.py @ 50662:12f13b13f414 stable
revlog: avoid possible collision between directory and temporary index
Since 6.4, we create a temporary index file to write the split data without
overwriting the inline version too early. However, the store encoding does not
prevent these new `.i.s` file to collide with a directory with the same name.
While the odds for such a collision to happens are fairly low, the collision
would prevent Mercurial from working.
The store encoding have a mitigation solution in place to prevent such
collisions from happening for `.i` and `.d` files, but not for other extensions.
We cannot update this encoding scheme to solve the issue since it would diverge
from older version of Mercurial.
Instead, we create an alternative directory tree dedicated to such files.
The use of the `.i` extension combined with store encoding will prevent
collisions there.
author | Pierre-Yves David <pierre-yves.david@octobus.net> |
---|---|
date | Thu, 08 Jun 2023 14:28:21 +0200 |
parents | 3eac92509484 |
children | 18c8c18993f0 |
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# policy.py - module policy logic for Mercurial. # # Copyright 2015 Gregory Szorc <gregory.szorc@gmail.com> # # This software may be used and distributed according to the terms of the # GNU General Public License version 2 or any later version. import os import sys from .pycompat import getattr # Rules for how modules can be loaded. Values are: # # c - require C extensions # rust+c - require Rust and C extensions # rust+c-allow - allow Rust and C extensions with fallback to pure Python # for each # allow - allow pure Python implementation when C loading fails # cffi - required cffi versions (implemented within pure module) # cffi-allow - allow pure Python implementation if cffi version is missing # py - only load pure Python modules # # By default, fall back to the pure modules so the in-place build can # run without recompiling the C extensions. This will be overridden by # __modulepolicy__ generated by setup.py. policy = b'allow' _packageprefs = { # policy: (versioned package, pure package) b'c': ('cext', None), b'allow': ('cext', 'pure'), b'cffi': ('cffi', None), b'cffi-allow': ('cffi', 'pure'), b'py': (None, 'pure'), # For now, rust policies impact importrust only b'rust+c': ('cext', None), b'rust+c-allow': ('cext', 'pure'), } try: from . import __modulepolicy__ policy = __modulepolicy__.modulepolicy except ImportError: pass # PyPy doesn't load C extensions. # # The canonical way to do this is to test platform.python_implementation(). # But we don't import platform and don't bloat for it here. if '__pypy__' in sys.builtin_module_names: policy = b'cffi' # Environment variable can always force settings. if 'HGMODULEPOLICY' in os.environ: policy = os.environ['HGMODULEPOLICY'].encode('utf-8') def _importfrom(pkgname, modname): # from .<pkgname> import <modname> (where . is looked through this module) fakelocals = {} pkg = __import__(pkgname, globals(), fakelocals, [modname], level=1) try: fakelocals[modname] = mod = getattr(pkg, modname) except AttributeError: raise ImportError('cannot import name %s' % modname) # force import; fakelocals[modname] may be replaced with the real module getattr(mod, '__doc__', None) return fakelocals[modname] # keep in sync with "version" in C modules _cextversions = { ('cext', 'base85'): 1, ('cext', 'bdiff'): 3, ('cext', 'mpatch'): 1, ('cext', 'osutil'): 4, ('cext', 'parsers'): 21, } # map import request to other package or module _modredirects = { ('cext', 'charencode'): ('cext', 'parsers'), ('cffi', 'base85'): ('pure', 'base85'), ('cffi', 'charencode'): ('pure', 'charencode'), ('cffi', 'parsers'): ('pure', 'parsers'), } def _checkmod(pkgname, modname, mod): expected = _cextversions.get((pkgname, modname)) actual = getattr(mod, 'version', None) if actual != expected: raise ImportError( 'cannot import module %s.%s ' '(expected version: %d, actual: %r)' % (pkgname, modname, expected, actual) ) def importmod(modname): """Import module according to policy and check API version""" try: verpkg, purepkg = _packageprefs[policy] except KeyError: raise ImportError('invalid HGMODULEPOLICY %r' % policy) assert verpkg or purepkg if verpkg: pn, mn = _modredirects.get((verpkg, modname), (verpkg, modname)) try: mod = _importfrom(pn, mn) if pn == verpkg: _checkmod(pn, mn, mod) return mod except ImportError: if not purepkg: raise pn, mn = _modredirects.get((purepkg, modname), (purepkg, modname)) return _importfrom(pn, mn) def _isrustpermissive(): """Assuming the policy is a Rust one, tell if it's permissive.""" return policy.endswith(b'-allow') def importrust(modname, member=None, default=None): """Import Rust module according to policy and availability. If policy isn't a Rust one, this returns `default`. If either the module or its member is not available, this returns `default` if policy is permissive and raises `ImportError` if not. """ if not policy.startswith(b'rust'): return default try: mod = _importfrom('rustext', modname) except ImportError: if _isrustpermissive(): return default raise if member is None: return mod try: return getattr(mod, member) except AttributeError: if _isrustpermissive(): return default raise ImportError("Cannot import name %s" % member)