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Viewing / Editing File: _compat.py

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# flake8: noqa

import abc
import sys
import pathlib
from contextlib import suppress

if sys.version_info >= (3, 10):
    from zipfile import Path as ZipPath  # type: ignore
else:
    from ..zipp import Path as ZipPath  # type: ignore


try:
    from typing import runtime_checkable  # type: ignore
except ImportError:

    def runtime_checkable(cls):  # type: ignore
        return cls


try:
    from typing import Protocol  # type: ignore
except ImportError:
    Protocol = abc.ABC  # type: ignore


class TraversableResourcesLoader:
    """
    Adapt loaders to provide TraversableResources and other
    compatibility.

    Used primarily for Python 3.9 and earlier where the native
    loaders do not yet implement TraversableResources.
    """

    def __init__(self, spec):
        self.spec = spec

    @property
    def path(self):
        return self.spec.origin

    def get_resource_reader(self, name):
        from . import readers, _adapters

        def _zip_reader(spec):
            with suppress(AttributeError):
                return readers.ZipReader(spec.loader, spec.name)

        def _namespace_reader(spec):
            with suppress(AttributeError, ValueError):
                return readers.NamespaceReader(spec.submodule_search_locations)

        def _available_reader(spec):
            with suppress(AttributeError):
                return spec.loader.get_resource_reader(spec.name)

        def _native_reader(spec):
            reader = _available_reader(spec)
            return reader if hasattr(reader, 'files') else None

        def _file_reader(spec):
            try:
                path = pathlib.Path(self.path)
            except TypeError:
                return None
            if path.exists():
                return readers.FileReader(self)

        return (
            # native reader if it supplies 'files'
            _native_reader(self.spec)
            or
            # local ZipReader if a zip module
            _zip_reader(self.spec)
            or
            # local NamespaceReader if a namespace module
            _namespace_reader(self.spec)
            or
            # local FileReader
            _file_reader(self.spec)
            # fallback - adapt the spec ResourceReader to TraversableReader
            or _adapters.CompatibilityFiles(self.spec)
        )


def wrap_spec(package):
    """
    Construct a package spec with traversable compatibility
    on the spec/loader/reader.

    Supersedes _adapters.wrap_spec to use TraversableResourcesLoader
    from above for older Python compatibility (<3.10).
    """
    from . import _adapters

    return _adapters.SpecLoaderAdapter(package.__spec__, TraversableResourcesLoader)
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