Mercurial > hg
view hgdemandimport/__init__.py @ 50336:cf4d2f31660d stable
chg: populate CHGHG if not set
Normally, chg determines which `hg` executable to use by first consulting the
`$CHGHG` and `$HG` environment variables, and if neither are present defaults
to the `hg` found in the user's `$PATH`. If built with the `HGPATHREL` compiler
flag, chg will instead assume that there exists an `hg` executable in the same
directory as the `chg` binary and attempt to use that.
This can cause problems in situations where there are multiple actively-used
Mercurial installations on the same system. When a `chg` client connects to a
running command server, the server process performs some basic validation to
determine whether a new command server needs to be spawned. These checks include
things like checking certain "sensitive" environment variables and config
sections, as well as checking whether the mtime of the extensions, hg's
`__version__.py` module, and the Python interpreter have changed.
Crucially, the command server doesn't explicitly check whether the executable it
is running from matches the executable that the `chg` client would have
otherwise invoked had there been no existing command server process. Without
`HGPATHREL`, this still gets implicitly checked during the validation step,
because the only way to specify an alternate hg executable (apart from `$PATH`)
is via the `$CHGHG` and `$HG` environment variables, both of which are checked.
With `HGPATHREL`, however, the command server has no way of knowing which hg
executable the client would have run. This means that a client located at
`/version_B/bin/chg` will happily connect to a command server running
`/version_A/bin/hg` instead of `/version_B/bin/hg` as expected. A simple
solution is to have the client set `$CHGHG` itself, which then allows the
command server's environment validation to work as intended.
I have tested this manually using two locally built hg installations and it
seems to work with no ill effects. That said, I'm not sure how to write an
automated test for this since the `chg` available to the tests isn't even built
with the `HGPATHREL` compiler flag to begin with.
author | Arun Kulshreshtha <akulshreshtha@janestreet.com> |
---|---|
date | Mon, 27 Mar 2023 17:30:14 -0400 |
parents | 127d33e63d1a |
children | 80c8dcfb73c6 |
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# hgdemandimport - 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. '''demandimport - automatic demand-loading of modules''' # This is in a separate package from mercurial because in Python 3, # demand loading is per-package. Keeping demandimport in the mercurial package # would disable demand loading for any modules in mercurial. import os import sys from . import demandimportpy3 as demandimport # Full module names which can't be lazy imported. # Extensions can add to this set. IGNORES = { '__future__', '_hashlib', # ImportError during pkg_resources/__init__.py:fixup_namespace_package '_imp', '_xmlplus', 'fcntl', 'nt', # pathlib2 tests the existence of built-in 'nt' module 'win32com.gen_py', 'win32com.shell', # 'appdirs' tries to import win32com.shell '_winreg', # 2.7 mimetypes needs immediate ImportError 'pythoncom', # imported by tarfile, not available under Windows 'pwd', 'grp', # imported by profile, itself imported by hotshot.stats, # not available under Windows 'resource', # this trips up many extension authors 'gtk', # setuptools' pkg_resources.py expects "from __main__ import x" to # raise ImportError if x not defined '__main__', '_ast', # https://bugs.python.org/issue41631 '_ssl', # conditional imports in the stdlib, issue1964 '_sre', # issue4920 'rfc822', 'mimetools', 'sqlalchemy.events', # has import-time side effects (issue5085) 'sqlalchemy.dialects', # similar problems as above # setuptools 8 expects this module to explode early when not on windows 'distutils.msvc9compiler', '__builtin__', 'builtins', 'urwid.command_map', # for pudb 'lzma', } _pypy = '__pypy__' in sys.builtin_module_names if _pypy: # _ctypes.pointer is shadowed by "from ... import pointer" (PyPy 5) IGNORES.add('_ctypes.pointer') # pure Python module on PyPy, must be loaded to raise ModuleNotFoundError # on non-Windows platforms IGNORES.add('msvcrt') demandimport.init(IGNORES) # Re-export. isenabled = demandimport.isenabled disable = demandimport.disable deactivated = demandimport.deactivated def enable(): # chg pre-imports modules so do not enable demandimport for it if ( 'CHGINTERNALMARK' not in os.environ and os.environ.get('HGDEMANDIMPORT') != 'disable' ): demandimport.enable()