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"""Patches that are applied at runtime to the virtual environment"""
# -*- coding: utf-8 -*-
import os
import sys
VIRTUALENV_PATCH_FILE = os.path.join(__file__)
def patch_dist(dist):
"""
Distutils allows user to configure some arguments via a configuration file:
https://docs.python.org/3/install/index.html#distutils-configuration-files
Some of this arguments though don't make sense in context of the virtual environment files, let's fix them up.
"""
# we cannot allow some install config as that would get packages installed outside of the virtual environment
old_parse_config_files = dist.Distribution.parse_config_files
def parse_config_files(self, *args, **kwargs):
result = old_parse_config_files(self, *args, **kwargs)
install = self.get_option_dict("install")
if "prefix" in install: # the prefix governs where to install the libraries
install["prefix"] = VIRTUALENV_PATCH_FILE, os.path.abspath(sys.prefix)
for base in ("purelib", "platlib", "headers", "scripts", "data"):
key = "install_{}".format(base)
if key in install: # do not allow global configs to hijack venv paths
install.pop(key, None)
return result
dist.Distribution.parse_config_files = parse_config_files
# Import hook that patches some modules to ignore configuration values that break package installation in case
# of virtual environments.
_DISTUTILS_PATCH = "distutils.dist", "setuptools.dist"
if sys.version_info > (3, 4):
# https://docs.python.org/3/library/importlib.html#setting-up-an-importer
class _Finder:
"""A meta path finder that allows patching the imported distutils modules"""
fullname = None
# lock[0] is threading.Lock(), but initialized lazily to avoid importing threading very early at startup,
# because there are gevent-based applications that need to be first to import threading by themselves.
# See https://github.com/pypa/virtualenv/issues/1895 for details.
lock = []
def find_spec(self, fullname, path, target=None): # noqa: U100
if fullname in _DISTUTILS_PATCH and self.fullname is None:
# initialize lock[0] lazily
if len(self.lock) == 0:
import threading
lock = threading.Lock()
# there is possibility that two threads T1 and T2 are simultaneously running into find_spec,
# observing .lock as empty, and further going into hereby initialization. However due to the GIL,
# list.append() operation is atomic and this way only one of the threads will "win" to put the lock
# - that every thread will use - into .lock[0].
# https://docs.python.org/3/faq/library.html#what-kinds-of-global-value-mutation-are-thread-safe
self.lock.append(lock)
from functools import partial
from importlib.util import find_spec
with self.lock[0]:
self.fullname = fullname
try:
spec = find_spec(fullname, path)
if spec is not None:
# https://www.python.org/dev/peps/pep-0451/#how-loading-will-work
is_new_api = hasattr(spec.loader, "exec_module")
func_name = "exec_module" if is_new_api else "load_module"
old = getattr(spec.loader, func_name)
func = self.exec_module if is_new_api else self.load_module
if old is not func:
try:
setattr(spec.loader, func_name, partial(func, old))
except AttributeError:
pass # C-Extension loaders are r/o such as zipimporter with <python 3.7
return spec
finally:
self.fullname = None
@staticmethod
def exec_module(old, module):
old(module)
if module.__name__ in _DISTUTILS_PATCH:
patch_dist(module)
@staticmethod
def load_module(old, name):
module = old(name)
if module.__name__ in _DISTUTILS_PATCH:
patch_dist(module)
return module
sys.meta_path.insert(0, _Finder())
else:
# https://www.python.org/dev/peps/pep-0302/
from imp import find_module
from pkgutil import ImpImporter, ImpLoader
class _VirtualenvImporter(object, ImpImporter):
def __init__(self, path=None):
object.__init__(self)
ImpImporter.__init__(self, path)
def find_module(self, fullname, path=None):
if fullname in _DISTUTILS_PATCH:
try:
return _VirtualenvLoader(fullname, *find_module(fullname.split(".")[-1], path))
except ImportError:
pass
return None
class _VirtualenvLoader(object, ImpLoader):
def __init__(self, fullname, file, filename, etc):
object.__init__(self)
ImpLoader.__init__(self, fullname, file, filename, etc)
def load_module(self, fullname):
module = super(_VirtualenvLoader, self).load_module(fullname)
patch_dist(module)
module.__loader__ = None # distlib fallback
return module
sys.meta_path.append(_VirtualenvImporter())
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