codekingpro/portable-devtools

1import platform2import sys3 4__all__ = ['install', 'NullFinder']5 6 7def install(cls):8    """9    Class decorator for installation on sys.meta_path.10 11    Adds the backport DistributionFinder to sys.meta_path and12    attempts to disable the finder functionality of the stdlib13    DistributionFinder.14    """15    sys.meta_path.append(cls())16    disable_stdlib_finder()17    return cls18 19 20def disable_stdlib_finder():21    """22    Give the backport primacy for discovering path-based distributions23    by monkey-patching the stdlib O_O.24 25    See #91 for more background for rationale on this sketchy26    behavior.27    """28 29    def matches(finder):30        return getattr(31            finder, '__module__', None32        ) == '_frozen_importlib_external' and hasattr(finder, 'find_distributions')33 34    for finder in filter(matches, sys.meta_path):  # pragma: nocover35        del finder.find_distributions36 37 38class NullFinder:39    """40    A "Finder" (aka "MetaPathFinder") that never finds any modules,41    but may find distributions.42    """43 44    @staticmethod45    def find_spec(*args, **kwargs):46        return None47 48 49def pypy_partial(val):50    """51    Adjust for variable stacklevel on partial under PyPy.52 53    Workaround for #327.54    """55    is_pypy = platform.python_implementation() == 'PyPy'56    return val + is_pypy57