import platform import sys __all__ = ['install', 'NullFinder'] 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 "MetaPathFinder") that never finds any modules, but may find distributions. """ @staticmethod def find_spec(*args, **kwargs): return None 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