mercurial/policy.py
author Kyle Lippincott <spectral@google.com>
Wed, 02 Dec 2020 12:33:51 -0800
changeset 46018 8b0a3ff5ed12
parent 45131 61e7464477ac
child 47043 12450fbea288
permissions -rw-r--r--
statprof: separate functions and "line", assume 4 digit line numbers Previously, the profile output looked like this (I've removed many lines that are mostly inconsequential): ``` | 100.0% 0.02s hg: <module> line 43: dispatch.run() | 100.0% 0.02s dispatch.py: run line 115: status = dispatch(req) | 100.0% 0.02s dispatch.py: _runcatchfunc line 432: return _dispatch(req) \ 50.0% 0.01s dispatch.py: _dispatch line 1228: return runcommand( | 50.0% 0.01s dispatch.py: runcommand line 883: ret = _runcommand(ui, optio... | 50.0% 0.01s dispatch.py: _runcommand line 1240: return cmdfunc() | 50.0% 0.01s localrepo.py: __getitem__ line 1670: quick_access = self._quick_... | 50.0% 0.01s localrepo.py: _quick_access_changeidline 1650: return self._quick_access_c... | 50.0% 0.01s localrepo.py: __get__ line 179: return getattr(unfi, self.n... | 50.0% 0.01s util.py: __get__ line 1747: result = self.func(obj) | 50.0% 0.01s localrepo.py: _quick_access_changeid_wcline 1611: cl = self.unfiltered().chan... | 50.0% 0.01s localrepo.py: __get__ line 110: return super(_basefilecache... | 50.0% 0.01s util.py: __getattribute__line 245: self.__spec__.loader.exec_m... | 50.0% 0.01s <frozen importlib._bootstrap_external>: exec_moduleline 783: | 50.0% 0.01s <frozen importlib._bootstrap>: _call_with_frames_removedline 219: | 50.0% 0.01s changelog.py: <module> line 376: class changelog(revlog.revl... | 50.0% 0.01s util.py: __getattribute__line 245: self.__spec__.loader.exec_m... | 50.0% 0.01s <frozen importlib._bootstrap_external>: exec_moduleline 779: | 50.0% 0.01s <frozen importlib._bootstrap_external>: get_codeline 868: | 50.0% 0.01s <frozen importlib._bootstrap_external>: path_statsline 1012: | 50.0% 0.01s <frozen importlib._bootstrap_external>: _path_statline 87: ``` This has a few problems, though I'm only addressing some of them. 1. If the stuff before "line ###" is long, there's no separation between the function name and the "line" string. 2. If the stuff before "line ###" is really long, there's excessive separation between the "line" string and the line number. 3. We frequently have 4-digit line numbers, the code on the right wasn't dynamically indented and ended up quite messy looking. To solve these problems, I've added a ", " prefix before "line" iff it would otherwise not have any separation such as spaces. I've added a 'max' so that we never use a negative width (which is the cause of problem #2 above), and I've added a default assumption of 4 digit line numbers (but again using a 'max' so this shouldn't cause problems if we go beyond that. With these changes, it now looks like this: ``` | 100.0% 0.02s hg: <module> line 43: dispatch.run() | 100.0% 0.02s dispatch.py: run line 115: status = dispatch(req) | 100.0% 0.02s dispatch.py: _runcatchfunc line 432: return _dispatch(req) \ 50.0% 0.01s dispatch.py: _dispatch line 1228: return runcommand( | 50.0% 0.01s dispatch.py: runcommand line 883: ret = _runcommand(ui, optio... | 50.0% 0.01s dispatch.py: _runcommand line 1240: return cmdfunc() | 50.0% 0.01s localrepo.py: __getitem__ line 1670: quick_access = self._quick_... | 50.0% 0.01s localrepo.py: _quick_access_changeid, line 1650: return self._quick_access_c... | 50.0% 0.01s localrepo.py: __get__ line 179: return getattr(unfi, self.n... | 50.0% 0.01s util.py: __get__ line 1747: result = self.func(obj) | 50.0% 0.01s localrepo.py: _quick_access_changeid_wc, line 1611: cl = self.unfiltered().chan... | 50.0% 0.01s localrepo.py: __get__ line 110: return super(_basefilecache... | 50.0% 0.01s util.py: __getattribute__, line 245: self.__spec__.loader.exec_m... | 50.0% 0.01s <frozen importlib._bootstrap_external>: exec_module, line 783: | 50.0% 0.01s <frozen importlib._bootstrap>: _call_with_frames_removed, line 219: | 50.0% 0.01s changelog.py: <module> line 376: class changelog(revlog.revl... | 50.0% 0.01s util.py: __getattribute__, line 245: self.__spec__.loader.exec_m... | 50.0% 0.01s <frozen importlib._bootstrap_external>: exec_module, line 779: | 50.0% 0.01s <frozen importlib._bootstrap_external>: get_code, line 868: | 50.0% 0.01s <frozen importlib._bootstrap_external>: path_stats, line 1012: | 50.0% 0.01s <frozen importlib._bootstrap_external>: _path_stat, line 87: ``` Differential Revision: https://phab.mercurial-scm.org/D9511

# 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.

from __future__ import absolute_import

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 sys.version_info[0] >= 3:
    if 'HGMODULEPOLICY' in os.environ:
        policy = os.environ['HGMODULEPOLICY'].encode('utf-8')
else:
    policy = os.environ.get('HGMODULEPOLICY', policy)


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'): 17,
}

# 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)