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73 lines
1.8 KiB
Python
73 lines
1.8 KiB
Python
2 years ago
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import sys
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import platform
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__all__ = ['install', 'NullFinder', 'Protocol']
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try:
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from typing import Protocol
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except ImportError: # pragma: no cover
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# Python 3.7 compatibility
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from typing_extensions import Protocol # type: ignore
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def install(cls):
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"""
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Class decorator for installation on sys.meta_path.
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Adds the backport DistributionFinder to sys.meta_path and
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attempts to disable the finder functionality of the stdlib
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DistributionFinder.
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"""
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sys.meta_path.append(cls())
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disable_stdlib_finder()
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return cls
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def disable_stdlib_finder():
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"""
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Give the backport primacy for discovering path-based distributions
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by monkey-patching the stdlib O_O.
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See #91 for more background for rationale on this sketchy
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behavior.
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"""
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def matches(finder):
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return getattr(
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finder, '__module__', None
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) == '_frozen_importlib_external' and hasattr(finder, 'find_distributions')
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for finder in filter(matches, sys.meta_path): # pragma: nocover
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del finder.find_distributions
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class NullFinder:
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"""
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A "Finder" (aka "MetaClassFinder") that never finds any modules,
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but may find distributions.
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"""
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@staticmethod
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def find_spec(*args, **kwargs):
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return None
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# In Python 2, the import system requires finders
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# to have a find_module() method, but this usage
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# is deprecated in Python 3 in favor of find_spec().
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# For the purposes of this finder (i.e. being present
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# on sys.meta_path but having no other import
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# system functionality), the two methods are identical.
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find_module = find_spec
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def pypy_partial(val):
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"""
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Adjust for variable stacklevel on partial under PyPy.
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Workaround for #327.
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"""
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is_pypy = platform.python_implementation() == 'PyPy'
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return val + is_pypy
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