| import sys |
| import platform |
| |
| |
| __all__ = ['install', 'NullFinder', 'Protocol'] |
| |
| |
| try: |
| from typing import Protocol |
| except ImportError: # pragma: no cover |
| from ..typing_extensions import Protocol # type: ignore |
| |
| |
| def install(cls): |
| """ |
| Class decorator for installation on sys.meta_path. |
| |
| Adds the backport DistributionFinder to sys.meta_path and |
| attempts to disable the finder functionality of the stdlib |
| DistributionFinder. |
| """ |
| sys.meta_path.append(cls()) |
| disable_stdlib_finder() |
| return cls |
| |
| |
| def disable_stdlib_finder(): |
| """ |
| Give the backport primacy for discovering path-based distributions |
| by monkey-patching the stdlib O_O. |
| |
| See #91 for more background for rationale on this sketchy |
| behavior. |
| """ |
| |
| def matches(finder): |
| return getattr( |
| finder, '__module__', None |
| ) == '_frozen_importlib_external' and hasattr(finder, 'find_distributions') |
| |
| for finder in filter(matches, sys.meta_path): # pragma: nocover |
| del finder.find_distributions |
| |
| |
| class NullFinder: |
| """ |
| A "Finder" (aka "MetaClassFinder") that never finds any modules, |
| but may find distributions. |
| """ |
| |
| @staticmethod |
| def find_spec(*args, **kwargs): |
| return None |
| |
| # In Python 2, the import system requires finders |
| # to have a find_module() method, but this usage |
| # is deprecated in Python 3 in favor of find_spec(). |
| # For the purposes of this finder (i.e. being present |
| # on sys.meta_path but having no other import |
| # system functionality), the two methods are identical. |
| find_module = find_spec |
| |
| |
| def pypy_partial(val): |
| """ |
| Adjust for variable stacklevel on partial under PyPy. |
| |
| Workaround for #327. |
| """ |
| is_pypy = platform.python_implementation() == 'PyPy' |
| return val + is_pypy |
