Revert "Remove importlib-metadata and importlib-resources"

This reverts commit 38435ae81c.

lib/importlib_resources/__init__.py

@@ -0,0 +1,17 @@
+"""Read resources contained within a package."""
+
+from ._common import (
+    as_file,
+    files,
+    Package,
+)
+
+from .abc import ResourceReader
+
+
+__all__ = [
+    'Package',
+    'ResourceReader',
+    'as_file',
+    'files',
+]

lib/importlib_resources/_adapters.py

@@ -0,0 +1,168 @@
+from contextlib import suppress
+from io import TextIOWrapper
+
+from . import abc
+
+
+class SpecLoaderAdapter:
+    """
+    Adapt a package spec to adapt the underlying loader.
+    """
+
+    def __init__(self, spec, adapter=lambda spec: spec.loader):
+        self.spec = spec
+        self.loader = adapter(spec)
+
+    def __getattr__(self, name):
+        return getattr(self.spec, name)
+
+
+class TraversableResourcesLoader:
+    """
+    Adapt a loader to provide TraversableResources.
+    """
+
+    def __init__(self, spec):
+        self.spec = spec
+
+    def get_resource_reader(self, name):
+        return CompatibilityFiles(self.spec)._native()
+
+
+def _io_wrapper(file, mode='r', *args, **kwargs):
+    if mode == 'r':
+        return TextIOWrapper(file, *args, **kwargs)
+    elif mode == 'rb':
+        return file
+    raise ValueError(f"Invalid mode value '{mode}', only 'r' and 'rb' are supported")
+
+
+class CompatibilityFiles:
+    """
+    Adapter for an existing or non-existent resource reader
+    to provide a compatibility .files().
+    """
+
+    class SpecPath(abc.Traversable):
+        """
+        Path tied to a module spec.
+        Can be read and exposes the resource reader children.
+        """
+
+        def __init__(self, spec, reader):
+            self._spec = spec
+            self._reader = reader
+
+        def iterdir(self):
+            if not self._reader:
+                return iter(())
+            return iter(
+                CompatibilityFiles.ChildPath(self._reader, path)
+                for path in self._reader.contents()
+            )
+
+        def is_file(self):
+            return False
+
+        is_dir = is_file
+
+        def joinpath(self, other):
+            if not self._reader:
+                return CompatibilityFiles.OrphanPath(other)
+            return CompatibilityFiles.ChildPath(self._reader, other)
+
+        @property
+        def name(self):
+            return self._spec.name
+
+        def open(self, mode='r', *args, **kwargs):
+            return _io_wrapper(self._reader.open_resource(None), mode, *args, **kwargs)
+
+    class ChildPath(abc.Traversable):
+        """
+        Path tied to a resource reader child.
+        Can be read but doesn't expose any meaningful children.
+        """
+
+        def __init__(self, reader, name):
+            self._reader = reader
+            self._name = name
+
+        def iterdir(self):
+            return iter(())
+
+        def is_file(self):
+            return self._reader.is_resource(self.name)
+
+        def is_dir(self):
+            return not self.is_file()
+
+        def joinpath(self, other):
+            return CompatibilityFiles.OrphanPath(self.name, other)
+
+        @property
+        def name(self):
+            return self._name
+
+        def open(self, mode='r', *args, **kwargs):
+            return _io_wrapper(
+                self._reader.open_resource(self.name), mode, *args, **kwargs
+            )
+
+    class OrphanPath(abc.Traversable):
+        """
+        Orphan path, not tied to a module spec or resource reader.
+        Can't be read and doesn't expose any meaningful children.
+        """
+
+        def __init__(self, *path_parts):
+            if len(path_parts) < 1:
+                raise ValueError('Need at least one path part to construct a path')
+            self._path = path_parts
+
+        def iterdir(self):
+            return iter(())
+
+        def is_file(self):
+            return False
+
+        is_dir = is_file
+
+        def joinpath(self, other):
+            return CompatibilityFiles.OrphanPath(*self._path, other)
+
+        @property
+        def name(self):
+            return self._path[-1]
+
+        def open(self, mode='r', *args, **kwargs):
+            raise FileNotFoundError("Can't open orphan path")
+
+    def __init__(self, spec):
+        self.spec = spec
+
+    @property
+    def _reader(self):
+        with suppress(AttributeError):
+            return self.spec.loader.get_resource_reader(self.spec.name)
+
+    def _native(self):
+        """
+        Return the native reader if it supports files().
+        """
+        reader = self._reader
+        return reader if hasattr(reader, 'files') else self
+
+    def __getattr__(self, attr):
+        return getattr(self._reader, attr)
+
+    def files(self):
+        return CompatibilityFiles.SpecPath(self.spec, self._reader)
+
+
+def wrap_spec(package):
+    """
+    Construct a package spec with traversable compatibility
+    on the spec/loader/reader.
+    """
+    return SpecLoaderAdapter(package.__spec__, TraversableResourcesLoader)

lib/importlib_resources/_common.py

@@ -0,0 +1,207 @@
+import os
+import pathlib
+import tempfile
+import functools
+import contextlib
+import types
+import importlib
+import inspect
+import warnings
+import itertools
+
+from typing import Union, Optional, cast
+from .abc import ResourceReader, Traversable
+
+from ._compat import wrap_spec
+
+Package = Union[types.ModuleType, str]
+Anchor = Package
+
+
+def package_to_anchor(func):
+    """
+    Replace 'package' parameter as 'anchor' and warn about the change.
+
+    Other errors should fall through.
+
+    >>> files('a', 'b')
+    Traceback (most recent call last):
+    TypeError: files() takes from 0 to 1 positional arguments but 2 were given
+    """
+    undefined = object()
+
+    @functools.wraps(func)
+    def wrapper(anchor=undefined, package=undefined):
+        if package is not undefined:
+            if anchor is not undefined:
+                return func(anchor, package)
+            warnings.warn(
+                "First parameter to files is renamed to 'anchor'",
+                DeprecationWarning,
+                stacklevel=2,
+            )
+            return func(package)
+        elif anchor is undefined:
+            return func()
+        return func(anchor)
+
+    return wrapper
+
+
+@package_to_anchor
+def files(anchor: Optional[Anchor] = None) -> Traversable:
+    """
+    Get a Traversable resource for an anchor.
+    """
+    return from_package(resolve(anchor))
+
+
+def get_resource_reader(package: types.ModuleType) -> Optional[ResourceReader]:
+    """
+    Return the package's loader if it's a ResourceReader.
+    """
+    # We can't use
+    # a issubclass() check here because apparently abc.'s __subclasscheck__()
+    # hook wants to create a weak reference to the object, but
+    # zipimport.zipimporter does not support weak references, resulting in a
+    # TypeError.  That seems terrible.
+    spec = package.__spec__
+    reader = getattr(spec.loader, 'get_resource_reader', None)  # type: ignore
+    if reader is None:
+        return None
+    return reader(spec.name)  # type: ignore
+
+
+@functools.singledispatch
+def resolve(cand: Optional[Anchor]) -> types.ModuleType:
+    return cast(types.ModuleType, cand)
+
+
+@resolve.register
+def _(cand: str) -> types.ModuleType:
+    return importlib.import_module(cand)
+
+
+@resolve.register
+def _(cand: None) -> types.ModuleType:
+    return resolve(_infer_caller().f_globals['__name__'])
+
+
+def _infer_caller():
+    """
+    Walk the stack and find the frame of the first caller not in this module.
+    """
+
+    def is_this_file(frame_info):
+        return frame_info.filename == __file__
+
+    def is_wrapper(frame_info):
+        return frame_info.function == 'wrapper'
+
+    not_this_file = itertools.filterfalse(is_this_file, inspect.stack())
+    # also exclude 'wrapper' due to singledispatch in the call stack
+    callers = itertools.filterfalse(is_wrapper, not_this_file)
+    return next(callers).frame
+
+
+def from_package(package: types.ModuleType):
+    """
+    Return a Traversable object for the given package.
+
+    """
+    spec = wrap_spec(package)
+    reader = spec.loader.get_resource_reader(spec.name)
+    return reader.files()
+
+
+@contextlib.contextmanager
+def _tempfile(
+    reader,
+    suffix='',
+    # gh-93353: Keep a reference to call os.remove() in late Python
+    # finalization.
+    *,
+    _os_remove=os.remove,
+):
+    # Not using tempfile.NamedTemporaryFile as it leads to deeper 'try'
+    # blocks due to the need to close the temporary file to work on Windows
+    # properly.
+    fd, raw_path = tempfile.mkstemp(suffix=suffix)
+    try:
+        try:
+            os.write(fd, reader())
+        finally:
+            os.close(fd)
+        del reader
+        yield pathlib.Path(raw_path)
+    finally:
+        try:
+            _os_remove(raw_path)
+        except FileNotFoundError:
+            pass
+
+
+def _temp_file(path):
+    return _tempfile(path.read_bytes, suffix=path.name)
+
+
+def _is_present_dir(path: Traversable) -> bool:
+    """
+    Some Traversables implement ``is_dir()`` to raise an
+    exception (i.e. ``FileNotFoundError``) when the
+    directory doesn't exist. This function wraps that call
+    to always return a boolean and only return True
+    if there's a dir and it exists.
+    """
+    with contextlib.suppress(FileNotFoundError):
+        return path.is_dir()
+    return False
+
+
+@functools.singledispatch
+def as_file(path):
+    """
+    Given a Traversable object, return that object as a
+    path on the local file system in a context manager.
+    """
+    return _temp_dir(path) if _is_present_dir(path) else _temp_file(path)
+
+
+@as_file.register(pathlib.Path)
+@contextlib.contextmanager
+def _(path):
+    """
+    Degenerate behavior for pathlib.Path objects.
+    """
+    yield path
+
+
+@contextlib.contextmanager
+def _temp_path(dir: tempfile.TemporaryDirectory):
+    """
+    Wrap tempfile.TemporyDirectory to return a pathlib object.
+    """
+    with dir as result:
+        yield pathlib.Path(result)
+
+
+@contextlib.contextmanager
+def _temp_dir(path):
+    """
+    Given a traversable dir, recursively replicate the whole tree
+    to the file system in a context manager.
+    """
+    assert path.is_dir()
+    with _temp_path(tempfile.TemporaryDirectory()) as temp_dir:
+        yield _write_contents(temp_dir, path)
+
+
+def _write_contents(target, source):
+    child = target.joinpath(source.name)
+    if source.is_dir():
+        child.mkdir()
+        for item in source.iterdir():
+            _write_contents(child, item)
+    else:
+        child.write_bytes(source.read_bytes())
+    return child

lib/importlib_resources/_compat.py

@@ -0,0 +1,109 @@
+# flake8: noqa
+
+import abc
+import os
+import sys
+import pathlib
+from contextlib import suppress
+from typing import Union
+
+
+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 (
+            # 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)
+            or
+            # native reader if it supplies 'files'
+            _native_reader(self.spec)
+            or
+            # fallback - adapt the spec ResourceReader to TraversableReader
+            _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)
+
+
+if sys.version_info >= (3, 9):
+    StrPath = Union[str, os.PathLike[str]]
+else:
+    # PathLike is only subscriptable at runtime in 3.9+
+    StrPath = Union[str, "os.PathLike[str]"]

lib/importlib_resources/_itertools.py

@@ -0,0 +1,38 @@
+# from more_itertools 9.0
+def only(iterable, default=None, too_long=None):
+    """If *iterable* has only one item, return it.
+    If it has zero items, return *default*.
+    If it has more than one item, raise the exception given by *too_long*,
+    which is ``ValueError`` by default.
+    >>> only([], default='missing')
+    'missing'
+    >>> only([1])
+    1
+    >>> only([1, 2])  # doctest: +IGNORE_EXCEPTION_DETAIL
+    Traceback (most recent call last):
+    ...
+    ValueError: Expected exactly one item in iterable, but got 1, 2,
+     and perhaps more.'
+    >>> only([1, 2], too_long=TypeError)  # doctest: +IGNORE_EXCEPTION_DETAIL
+    Traceback (most recent call last):
+    ...
+    TypeError
+    Note that :func:`only` attempts to advance *iterable* twice to ensure there
+    is only one item.  See :func:`spy` or :func:`peekable` to check
+    iterable contents less destructively.
+    """
+    it = iter(iterable)
+    first_value = next(it, default)
+
+    try:
+        second_value = next(it)
+    except StopIteration:
+        pass
+    else:
+        msg = (
+            'Expected exactly one item in iterable, but got {!r}, {!r}, '
+            'and perhaps more.'.format(first_value, second_value)
+        )
+        raise too_long or ValueError(msg)
+
+    return first_value

lib/importlib_resources/abc.py

@@ -0,0 +1,170 @@
+import abc
+import io
+import itertools
+import pathlib
+from typing import Any, BinaryIO, Iterable, Iterator, NoReturn, Text, Optional
+
+from ._compat import runtime_checkable, Protocol, StrPath
+
+
+__all__ = ["ResourceReader", "Traversable", "TraversableResources"]
+
+
+class ResourceReader(metaclass=abc.ABCMeta):
+    """Abstract base class for loaders to provide resource reading support."""
+
+    @abc.abstractmethod
+    def open_resource(self, resource: Text) -> BinaryIO:
+        """Return an opened, file-like object for binary reading.
+
+        The 'resource' argument is expected to represent only a file name.
+        If the resource cannot be found, FileNotFoundError is raised.
+        """
+        # This deliberately raises FileNotFoundError instead of
+        # NotImplementedError so that if this method is accidentally called,
+        # it'll still do the right thing.
+        raise FileNotFoundError
+
+    @abc.abstractmethod
+    def resource_path(self, resource: Text) -> Text:
+        """Return the file system path to the specified resource.
+
+        The 'resource' argument is expected to represent only a file name.
+        If the resource does not exist on the file system, raise
+        FileNotFoundError.
+        """
+        # This deliberately raises FileNotFoundError instead of
+        # NotImplementedError so that if this method is accidentally called,
+        # it'll still do the right thing.
+        raise FileNotFoundError
+
+    @abc.abstractmethod
+    def is_resource(self, path: Text) -> bool:
+        """Return True if the named 'path' is a resource.
+
+        Files are resources, directories are not.
+        """
+        raise FileNotFoundError
+
+    @abc.abstractmethod
+    def contents(self) -> Iterable[str]:
+        """Return an iterable of entries in `package`."""
+        raise FileNotFoundError
+
+
+class TraversalError(Exception):
+    pass
+
+
+@runtime_checkable
+class Traversable(Protocol):
+    """
+    An object with a subset of pathlib.Path methods suitable for
+    traversing directories and opening files.
+
+    Any exceptions that occur when accessing the backing resource
+    may propagate unaltered.
+    """
+
+    @abc.abstractmethod
+    def iterdir(self) -> Iterator["Traversable"]:
+        """
+        Yield Traversable objects in self
+        """
+
+    def read_bytes(self) -> bytes:
+        """
+        Read contents of self as bytes
+        """
+        with self.open('rb') as strm:
+            return strm.read()
+
+    def read_text(self, encoding: Optional[str] = None) -> str:
+        """
+        Read contents of self as text
+        """
+        with self.open(encoding=encoding) as strm:
+            return strm.read()
+
+    @abc.abstractmethod
+    def is_dir(self) -> bool:
+        """
+        Return True if self is a directory
+        """
+
+    @abc.abstractmethod
+    def is_file(self) -> bool:
+        """
+        Return True if self is a file
+        """
+
+    def joinpath(self, *descendants: StrPath) -> "Traversable":
+        """
+        Return Traversable resolved with any descendants applied.
+
+        Each descendant should be a path segment relative to self
+        and each may contain multiple levels separated by
+        ``posixpath.sep`` (``/``).
+        """
+        if not descendants:
+            return self
+        names = itertools.chain.from_iterable(
+            path.parts for path in map(pathlib.PurePosixPath, descendants)
+        )
+        target = next(names)
+        matches = (
+            traversable for traversable in self.iterdir() if traversable.name == target
+        )
+        try:
+            match = next(matches)
+        except StopIteration:
+            raise TraversalError(
+                "Target not found during traversal.", target, list(names)
+            )
+        return match.joinpath(*names)
+
+    def __truediv__(self, child: StrPath) -> "Traversable":
+        """
+        Return Traversable child in self
+        """
+        return self.joinpath(child)
+
+    @abc.abstractmethod
+    def open(self, mode='r', *args, **kwargs):
+        """
+        mode may be 'r' or 'rb' to open as text or binary. Return a handle
+        suitable for reading (same as pathlib.Path.open).
+
+        When opening as text, accepts encoding parameters such as those
+        accepted by io.TextIOWrapper.
+        """
+
+    @property
+    @abc.abstractmethod
+    def name(self) -> str:
+        """
+        The base name of this object without any parent references.
+        """
+
+
+class TraversableResources(ResourceReader):
+    """
+    The required interface for providing traversable
+    resources.
+    """
+
+    @abc.abstractmethod
+    def files(self) -> "Traversable":
+        """Return a Traversable object for the loaded package."""
+
+    def open_resource(self, resource: StrPath) -> io.BufferedReader:
+        return self.files().joinpath(resource).open('rb')
+
+    def resource_path(self, resource: Any) -> NoReturn:
+        raise FileNotFoundError(resource)
+
+    def is_resource(self, path: StrPath) -> bool:
+        return self.files().joinpath(path).is_file()
+
+    def contents(self) -> Iterator[str]:
+        return (item.name for item in self.files().iterdir())

lib/importlib_resources/readers.py

@@ -0,0 +1,144 @@
+import collections
+import itertools
+import pathlib
+import operator
+
+from . import abc
+
+from ._itertools import only
+from ._compat import ZipPath
+
+
+def remove_duplicates(items):
+    return iter(collections.OrderedDict.fromkeys(items))
+
+
+class FileReader(abc.TraversableResources):
+    def __init__(self, loader):
+        self.path = pathlib.Path(loader.path).parent
+
+    def resource_path(self, resource):
+        """
+        Return the file system path to prevent
+        `resources.path()` from creating a temporary
+        copy.
+        """
+        return str(self.path.joinpath(resource))
+
+    def files(self):
+        return self.path
+
+
+class ZipReader(abc.TraversableResources):
+    def __init__(self, loader, module):
+        _, _, name = module.rpartition('.')
+        self.prefix = loader.prefix.replace('\\', '/') + name + '/'
+        self.archive = loader.archive
+
+    def open_resource(self, resource):
+        try:
+            return super().open_resource(resource)
+        except KeyError as exc:
+            raise FileNotFoundError(exc.args[0])
+
+    def is_resource(self, path):
+        """
+        Workaround for `zipfile.Path.is_file` returning true
+        for non-existent paths.
+        """
+        target = self.files().joinpath(path)
+        return target.is_file() and target.exists()
+
+    def files(self):
+        return ZipPath(self.archive, self.prefix)
+
+
+class MultiplexedPath(abc.Traversable):
+    """
+    Given a series of Traversable objects, implement a merged
+    version of the interface across all objects. Useful for
+    namespace packages which may be multihomed at a single
+    name.
+    """
+
+    def __init__(self, *paths):
+        self._paths = list(map(pathlib.Path, remove_duplicates(paths)))
+        if not self._paths:
+            message = 'MultiplexedPath must contain at least one path'
+            raise FileNotFoundError(message)
+        if not all(path.is_dir() for path in self._paths):
+            raise NotADirectoryError('MultiplexedPath only supports directories')
+
+    def iterdir(self):
+        children = (child for path in self._paths for child in path.iterdir())
+        by_name = operator.attrgetter('name')
+        groups = itertools.groupby(sorted(children, key=by_name), key=by_name)
+        return map(self._follow, (locs for name, locs in groups))
+
+    def read_bytes(self):
+        raise FileNotFoundError(f'{self} is not a file')
+
+    def read_text(self, *args, **kwargs):
+        raise FileNotFoundError(f'{self} is not a file')
+
+    def is_dir(self):
+        return True
+
+    def is_file(self):
+        return False
+
+    def joinpath(self, *descendants):
+        try:
+            return super().joinpath(*descendants)
+        except abc.TraversalError:
+            # One of the paths did not resolve (a directory does not exist).
+            # Just return something that will not exist.
+            return self._paths[0].joinpath(*descendants)
+
+    @classmethod
+    def _follow(cls, children):
+        """
+        Construct a MultiplexedPath if needed.
+
+        If children contains a sole element, return it.
+        Otherwise, return a MultiplexedPath of the items.
+        Unless one of the items is not a Directory, then return the first.
+        """
+        subdirs, one_dir, one_file = itertools.tee(children, 3)
+
+        try:
+            return only(one_dir)
+        except ValueError:
+            try:
+                return cls(*subdirs)
+            except NotADirectoryError:
+                return next(one_file)
+
+    def open(self, *args, **kwargs):
+        raise FileNotFoundError(f'{self} is not a file')
+
+    @property
+    def name(self):
+        return self._paths[0].name
+
+    def __repr__(self):
+        paths = ', '.join(f"'{path}'" for path in self._paths)
+        return f'MultiplexedPath({paths})'
+
+
+class NamespaceReader(abc.TraversableResources):
+    def __init__(self, namespace_path):
+        if 'NamespacePath' not in str(namespace_path):
+            raise ValueError('Invalid path')
+        self.path = MultiplexedPath(*list(namespace_path))
+
+    def resource_path(self, resource):
+        """
+        Return the file system path to prevent
+        `resources.path()` from creating a temporary
+        copy.
+        """
+        return str(self.path.joinpath(resource))
+
+    def files(self):
+        return self.path

lib/importlib_resources/simple.py

@@ -0,0 +1,106 @@
+"""
+Interface adapters for low-level readers.
+"""
+
+import abc
+import io
+import itertools
+from typing import BinaryIO, List
+
+from .abc import Traversable, TraversableResources
+
+
+class SimpleReader(abc.ABC):
+    """
+    The minimum, low-level interface required from a resource
+    provider.
+    """
+
+    @property
+    @abc.abstractmethod
+    def package(self) -> str:
+        """
+        The name of the package for which this reader loads resources.
+        """
+
+    @abc.abstractmethod
+    def children(self) -> List['SimpleReader']:
+        """
+        Obtain an iterable of SimpleReader for available
+        child containers (e.g. directories).
+        """
+
+    @abc.abstractmethod
+    def resources(self) -> List[str]:
+        """
+        Obtain available named resources for this virtual package.
+        """
+
+    @abc.abstractmethod
+    def open_binary(self, resource: str) -> BinaryIO:
+        """
+        Obtain a File-like for a named resource.
+        """
+
+    @property
+    def name(self):
+        return self.package.split('.')[-1]
+
+
+class ResourceContainer(Traversable):
+    """
+    Traversable container for a package's resources via its reader.
+    """
+
+    def __init__(self, reader: SimpleReader):
+        self.reader = reader
+
+    def is_dir(self):
+        return True
+
+    def is_file(self):
+        return False
+
+    def iterdir(self):
+        files = (ResourceHandle(self, name) for name in self.reader.resources)
+        dirs = map(ResourceContainer, self.reader.children())
+        return itertools.chain(files, dirs)
+
+    def open(self, *args, **kwargs):
+        raise IsADirectoryError()
+
+
+class ResourceHandle(Traversable):
+    """
+    Handle to a named resource in a ResourceReader.
+    """
+
+    def __init__(self, parent: ResourceContainer, name: str):
+        self.parent = parent
+        self.name = name  # type: ignore
+
+    def is_file(self):
+        return True
+
+    def is_dir(self):
+        return False
+
+    def open(self, mode='r', *args, **kwargs):
+        stream = self.parent.reader.open_binary(self.name)
+        if 'b' not in mode:
+            stream = io.TextIOWrapper(*args, **kwargs)
+        return stream
+
+    def joinpath(self, name):
+        raise RuntimeError("Cannot traverse into a resource")
+
+
+class TraversableReader(TraversableResources, SimpleReader):
+    """
+    A TraversableResources based on SimpleReader. Resource providers
+    may derive from this class to provide the TraversableResources
+    interface by supplying the SimpleReader interface.
+    """
+
+    def files(self):
+        return ResourceContainer(self)

lib/importlib_resources/tests/_compat.py

@@ -0,0 +1,32 @@
+import os
+
+
+try:
+    from test.support import import_helper  # type: ignore
+except ImportError:
+    # Python 3.9 and earlier
+    class import_helper:  # type: ignore
+        from test.support import (
+            modules_setup,
+            modules_cleanup,
+            DirsOnSysPath,
+            CleanImport,
+        )
+
+
+try:
+    from test.support import os_helper  # type: ignore
+except ImportError:
+    # Python 3.9 compat
+    class os_helper:  # type:ignore
+        from test.support import temp_dir
+
+
+try:
+    # Python 3.10
+    from test.support.os_helper import unlink
+except ImportError:
+    from test.support import unlink as _unlink
+
+    def unlink(target):
+        return _unlink(os.fspath(target))

lib/importlib_resources/tests/_path.py

@@ -0,0 +1,56 @@
+import pathlib
+import functools
+
+from typing import Dict, Union
+
+
+####
+# from jaraco.path 3.4.1
+
+FilesSpec = Dict[str, Union[str, bytes, 'FilesSpec']]  # type: ignore
+
+
+def build(spec: FilesSpec, prefix=pathlib.Path()):
+    """
+    Build a set of files/directories, as described by the spec.
+
+    Each key represents a pathname, and the value represents
+    the content. Content may be a nested directory.
+
+    >>> spec = {
+    ...     'README.txt': "A README file",
+    ...     "foo": {
+    ...         "__init__.py": "",
+    ...         "bar": {
+    ...             "__init__.py": "",
+    ...         },
+    ...         "baz.py": "# Some code",
+    ...     }
+    ... }
+    >>> target = getfixture('tmp_path')
+    >>> build(spec, target)
+    >>> target.joinpath('foo/baz.py').read_text(encoding='utf-8')
+    '# Some code'
+    """
+    for name, contents in spec.items():
+        create(contents, pathlib.Path(prefix) / name)
+
+
+@functools.singledispatch
+def create(content: Union[str, bytes, FilesSpec], path):
+    path.mkdir(exist_ok=True)
+    build(content, prefix=path)  # type: ignore
+
+
+@create.register
+def _(content: bytes, path):
+    path.write_bytes(content)
+
+
+@create.register
+def _(content: str, path):
+    path.write_text(content, encoding='utf-8')
+
+
+# end from jaraco.path
+####

lib/importlib_resources/tests/data01/utf-8.file

@@ -0,0 +1 @@
+Hello, UTF-8 world!

lib/importlib_resources/tests/data02/one/resource1.txt

@@ -0,0 +1 @@
+one resource

lib/importlib_resources/tests/data02/subdirectory/subsubdir/resource.txt

@@ -0,0 +1 @@
+a resource

lib/importlib_resources/tests/data02/two/resource2.txt

@@ -0,0 +1 @@
+two resource

lib/importlib_resources/tests/namespacedata01/utf-8.file

@@ -0,0 +1 @@
+Hello, UTF-8 world!

lib/importlib_resources/tests/test_compatibilty_files.py

@@ -0,0 +1,104 @@
+import io
+import unittest
+
+import importlib_resources as resources
+
+from importlib_resources._adapters import (
+    CompatibilityFiles,
+    wrap_spec,
+)
+
+from . import util
+
+
+class CompatibilityFilesTests(unittest.TestCase):
+    @property
+    def package(self):
+        bytes_data = io.BytesIO(b'Hello, world!')
+        return util.create_package(
+            file=bytes_data,
+            path='some_path',
+            contents=('a', 'b', 'c'),
+        )
+
+    @property
+    def files(self):
+        return resources.files(self.package)
+
+    def test_spec_path_iter(self):
+        self.assertEqual(
+            sorted(path.name for path in self.files.iterdir()),
+            ['a', 'b', 'c'],
+        )
+
+    def test_child_path_iter(self):
+        self.assertEqual(list((self.files / 'a').iterdir()), [])
+
+    def test_orphan_path_iter(self):
+        self.assertEqual(list((self.files / 'a' / 'a').iterdir()), [])
+        self.assertEqual(list((self.files / 'a' / 'a' / 'a').iterdir()), [])
+
+    def test_spec_path_is(self):
+        self.assertFalse(self.files.is_file())
+        self.assertFalse(self.files.is_dir())
+
+    def test_child_path_is(self):
+        self.assertTrue((self.files / 'a').is_file())
+        self.assertFalse((self.files / 'a').is_dir())
+
+    def test_orphan_path_is(self):
+        self.assertFalse((self.files / 'a' / 'a').is_file())
+        self.assertFalse((self.files / 'a' / 'a').is_dir())
+        self.assertFalse((self.files / 'a' / 'a' / 'a').is_file())
+        self.assertFalse((self.files / 'a' / 'a' / 'a').is_dir())
+
+    def test_spec_path_name(self):
+        self.assertEqual(self.files.name, 'testingpackage')
+
+    def test_child_path_name(self):
+        self.assertEqual((self.files / 'a').name, 'a')
+
+    def test_orphan_path_name(self):
+        self.assertEqual((self.files / 'a' / 'b').name, 'b')
+        self.assertEqual((self.files / 'a' / 'b' / 'c').name, 'c')
+
+    def test_spec_path_open(self):
+        self.assertEqual(self.files.read_bytes(), b'Hello, world!')
+        self.assertEqual(self.files.read_text(encoding='utf-8'), 'Hello, world!')
+
+    def test_child_path_open(self):
+        self.assertEqual((self.files / 'a').read_bytes(), b'Hello, world!')
+        self.assertEqual(
+            (self.files / 'a').read_text(encoding='utf-8'), 'Hello, world!'
+        )
+
+    def test_orphan_path_open(self):
+        with self.assertRaises(FileNotFoundError):
+            (self.files / 'a' / 'b').read_bytes()
+        with self.assertRaises(FileNotFoundError):
+            (self.files / 'a' / 'b' / 'c').read_bytes()
+
+    def test_open_invalid_mode(self):
+        with self.assertRaises(ValueError):
+            self.files.open('0')
+
+    def test_orphan_path_invalid(self):
+        with self.assertRaises(ValueError):
+            CompatibilityFiles.OrphanPath()
+
+    def test_wrap_spec(self):
+        spec = wrap_spec(self.package)
+        self.assertIsInstance(spec.loader.get_resource_reader(None), CompatibilityFiles)
+
+
+class CompatibilityFilesNoReaderTests(unittest.TestCase):
+    @property
+    def package(self):
+        return util.create_package_from_loader(None)
+
+    @property
+    def files(self):
+        return resources.files(self.package)
+
+    def test_spec_path_joinpath(self):
+        self.assertIsInstance(self.files / 'a', CompatibilityFiles.OrphanPath)

lib/importlib_resources/tests/test_contents.py

@@ -0,0 +1,43 @@
+import unittest
+import importlib_resources as resources
+
+from . import data01
+from . import util
+
+
+class ContentsTests:
+    expected = {
+        '__init__.py',
+        'binary.file',
+        'subdirectory',
+        'utf-16.file',
+        'utf-8.file',
+    }
+
+    def test_contents(self):
+        contents = {path.name for path in resources.files(self.data).iterdir()}
+        assert self.expected <= contents
+
+
+class ContentsDiskTests(ContentsTests, unittest.TestCase):
+    def setUp(self):
+        self.data = data01
+
+
+class ContentsZipTests(ContentsTests, util.ZipSetup, unittest.TestCase):
+    pass
+
+
+class ContentsNamespaceTests(ContentsTests, unittest.TestCase):
+    expected = {
+        # no __init__ because of namespace design
+        # no subdirectory as incidental difference in fixture
+        'binary.file',
+        'utf-16.file',
+        'utf-8.file',
+    }
+
+    def setUp(self):
+        from . import namespacedata01
+
+        self.data = namespacedata01

lib/importlib_resources/tests/test_custom.py

@@ -0,0 +1,45 @@
+import unittest
+import contextlib
+import pathlib
+
+import importlib_resources as resources
+from ..abc import TraversableResources, ResourceReader
+from . import util
+from ._compat import os_helper
+
+
+class SimpleLoader:
+    """
+    A simple loader that only implements a resource reader.
+    """
+
+    def __init__(self, reader: ResourceReader):
+        self.reader = reader
+
+    def get_resource_reader(self, package):
+        return self.reader
+
+
+class MagicResources(TraversableResources):
+    """
+    Magically returns the resources at path.
+    """
+
+    def __init__(self, path: pathlib.Path):
+        self.path = path
+
+    def files(self):
+        return self.path
+
+
+class CustomTraversableResourcesTests(unittest.TestCase):
+    def setUp(self):
+        self.fixtures = contextlib.ExitStack()
+        self.addCleanup(self.fixtures.close)
+
+    def test_custom_loader(self):
+        temp_dir = self.fixtures.enter_context(os_helper.temp_dir())
+        loader = SimpleLoader(MagicResources(temp_dir))
+        pkg = util.create_package_from_loader(loader)
+        files = resources.files(pkg)
+        assert files is temp_dir

lib/importlib_resources/tests/test_files.py

@@ -0,0 +1,112 @@
+import typing
+import textwrap
+import unittest
+import warnings
+import importlib
+import contextlib
+
+import importlib_resources as resources
+from ..abc import Traversable
+from . import data01
+from . import util
+from . import _path
+from ._compat import os_helper, import_helper
+
+
+@contextlib.contextmanager
+def suppress_known_deprecation():
+    with warnings.catch_warnings(record=True) as ctx:
+        warnings.simplefilter('default', category=DeprecationWarning)
+        yield ctx
+
+
+class FilesTests:
+    def test_read_bytes(self):
+        files = resources.files(self.data)
+        actual = files.joinpath('utf-8.file').read_bytes()
+        assert actual == b'Hello, UTF-8 world!\n'
+
+    def test_read_text(self):
+        files = resources.files(self.data)
+        actual = files.joinpath('utf-8.file').read_text(encoding='utf-8')
+        assert actual == 'Hello, UTF-8 world!\n'
+
+    @unittest.skipUnless(
+        hasattr(typing, 'runtime_checkable'),
+        "Only suitable when typing supports runtime_checkable",
+    )
+    def test_traversable(self):
+        assert isinstance(resources.files(self.data), Traversable)
+
+    def test_old_parameter(self):
+        """
+        Files used to take a 'package' parameter. Make sure anyone
+        passing by name is still supported.
+        """
+        with suppress_known_deprecation():
+            resources.files(package=self.data)
+
+
+class OpenDiskTests(FilesTests, unittest.TestCase):
+    def setUp(self):
+        self.data = data01
+
+
+class OpenZipTests(FilesTests, util.ZipSetup, unittest.TestCase):
+    pass
+
+
+class OpenNamespaceTests(FilesTests, unittest.TestCase):
+    def setUp(self):
+        from . import namespacedata01
+
+        self.data = namespacedata01
+
+
+class SiteDir:
+    def setUp(self):
+        self.fixtures = contextlib.ExitStack()
+        self.addCleanup(self.fixtures.close)
+        self.site_dir = self.fixtures.enter_context(os_helper.temp_dir())
+        self.fixtures.enter_context(import_helper.DirsOnSysPath(self.site_dir))
+        self.fixtures.enter_context(import_helper.CleanImport())
+
+
+class ModulesFilesTests(SiteDir, unittest.TestCase):
+    def test_module_resources(self):
+        """
+        A module can have resources found adjacent to the module.
+        """
+        spec = {
+            'mod.py': '',
+            'res.txt': 'resources are the best',
+        }
+        _path.build(spec, self.site_dir)
+        import mod
+
+        actual = resources.files(mod).joinpath('res.txt').read_text(encoding='utf-8')
+        assert actual == spec['res.txt']
+
+
+class ImplicitContextFilesTests(SiteDir, unittest.TestCase):
+    def test_implicit_files(self):
+        """
+        Without any parameter, files() will infer the location as the caller.
+        """
+        spec = {
+            'somepkg': {
+                '__init__.py': textwrap.dedent(
+                    """
+                    import importlib_resources as res
+                    val = res.files().joinpath('res.txt').read_text(encoding='utf-8')
+                    """
+                ),
+                'res.txt': 'resources are the best',
+            },
+        }
+        _path.build(spec, self.site_dir)
+        assert importlib.import_module('somepkg').val == 'resources are the best'
+
+
+if __name__ == '__main__':
+    unittest.main()

lib/importlib_resources/tests/test_open.py

@@ -0,0 +1,85 @@
+import unittest
+
+import importlib_resources as resources
+from . import data01
+from . import util
+
+
+class CommonBinaryTests(util.CommonTests, unittest.TestCase):
+    def execute(self, package, path):
+        target = resources.files(package).joinpath(path)
+        with target.open('rb'):
+            pass
+
+
+class CommonTextTests(util.CommonTests, unittest.TestCase):
+    def execute(self, package, path):
+        target = resources.files(package).joinpath(path)
+        with target.open(encoding='utf-8'):
+            pass
+
+
+class OpenTests:
+    def test_open_binary(self):
+        target = resources.files(self.data) / 'binary.file'
+        with target.open('rb') as fp:
+            result = fp.read()
+            self.assertEqual(result, b'\x00\x01\x02\x03')
+
+    def test_open_text_default_encoding(self):
+        target = resources.files(self.data) / 'utf-8.file'
+        with target.open(encoding='utf-8') as fp:
+            result = fp.read()
+            self.assertEqual(result, 'Hello, UTF-8 world!\n')
+
+    def test_open_text_given_encoding(self):
+        target = resources.files(self.data) / 'utf-16.file'
+        with target.open(encoding='utf-16', errors='strict') as fp:
+            result = fp.read()
+        self.assertEqual(result, 'Hello, UTF-16 world!\n')
+
+    def test_open_text_with_errors(self):
+        """
+        Raises UnicodeError without the 'errors' argument.
+        """
+        target = resources.files(self.data) / 'utf-16.file'
+        with target.open(encoding='utf-8', errors='strict') as fp:
+            self.assertRaises(UnicodeError, fp.read)
+        with target.open(encoding='utf-8', errors='ignore') as fp:
+            result = fp.read()
+        self.assertEqual(
+            result,
+            'H\x00e\x00l\x00l\x00o\x00,\x00 '
+            '\x00U\x00T\x00F\x00-\x001\x006\x00 '
+            '\x00w\x00o\x00r\x00l\x00d\x00!\x00\n\x00',
+        )
+
+    def test_open_binary_FileNotFoundError(self):
+        target = resources.files(self.data) / 'does-not-exist'
+        with self.assertRaises(FileNotFoundError):
+            target.open('rb')
+
+    def test_open_text_FileNotFoundError(self):
+        target = resources.files(self.data) / 'does-not-exist'
+        with self.assertRaises(FileNotFoundError):
+            target.open(encoding='utf-8')
+
+
+class OpenDiskTests(OpenTests, unittest.TestCase):
+    def setUp(self):
+        self.data = data01
+
+
+class OpenDiskNamespaceTests(OpenTests, unittest.TestCase):
+    def setUp(self):
+        from . import namespacedata01
+
+        self.data = namespacedata01
+
+
+class OpenZipTests(OpenTests, util.ZipSetup, unittest.TestCase):
+    pass
+
+
+if __name__ == '__main__':
+    unittest.main()

lib/importlib_resources/tests/test_path.py

@@ -0,0 +1,69 @@
+import io
+import unittest
+
+import importlib_resources as resources
+from . import data01
+from . import util
+
+
+class CommonTests(util.CommonTests, unittest.TestCase):
+    def execute(self, package, path):
+        with resources.as_file(resources.files(package).joinpath(path)):
+            pass
+
+
+class PathTests:
+    def test_reading(self):
+        """
+        Path should be readable.
+
+        Test also implicitly verifies the returned object is a pathlib.Path
+        instance.
+        """
+        target = resources.files(self.data) / 'utf-8.file'
+        with resources.as_file(target) as path:
+            self.assertTrue(path.name.endswith("utf-8.file"), repr(path))
+            # pathlib.Path.read_text() was introduced in Python 3.5.
+            with path.open('r', encoding='utf-8') as file:
+                text = file.read()
+            self.assertEqual('Hello, UTF-8 world!\n', text)
+
+
+class PathDiskTests(PathTests, unittest.TestCase):
+    data = data01
+
+    def test_natural_path(self):
+        """
+        Guarantee the internal implementation detail that
+        file-system-backed resources do not get the tempdir
+        treatment.
+        """
+        target = resources.files(self.data) / 'utf-8.file'
+        with resources.as_file(target) as path:
+            assert 'data' in str(path)
+
+
+class PathMemoryTests(PathTests, unittest.TestCase):
+    def setUp(self):
+        file = io.BytesIO(b'Hello, UTF-8 world!\n')
+        self.addCleanup(file.close)
+        self.data = util.create_package(
+            file=file, path=FileNotFoundError("package exists only in memory")
+        )
+        self.data.__spec__.origin = None
+        self.data.__spec__.has_location = False
+
+
+class PathZipTests(PathTests, util.ZipSetup, unittest.TestCase):
+    def test_remove_in_context_manager(self):
+        """
+        It is not an error if the file that was temporarily stashed on the
+        file system is removed inside the `with` stanza.
+        """
+        target = resources.files(self.data) / 'utf-8.file'
+        with resources.as_file(target) as path:
+            path.unlink()
+
+
+if __name__ == '__main__':
+    unittest.main()

lib/importlib_resources/tests/test_read.py

@@ -0,0 +1,82 @@
+import unittest
+import importlib_resources as resources
+
+from . import data01
+from . import util
+from importlib import import_module
+
+
+class CommonBinaryTests(util.CommonTests, unittest.TestCase):
+    def execute(self, package, path):
+        resources.files(package).joinpath(path).read_bytes()
+
+
+class CommonTextTests(util.CommonTests, unittest.TestCase):
+    def execute(self, package, path):
+        resources.files(package).joinpath(path).read_text(encoding='utf-8')
+
+
+class ReadTests:
+    def test_read_bytes(self):
+        result = resources.files(self.data).joinpath('binary.file').read_bytes()
+        self.assertEqual(result, b'\0\1\2\3')
+
+    def test_read_text_default_encoding(self):
+        result = (
+            resources.files(self.data)
+            .joinpath('utf-8.file')
+            .read_text(encoding='utf-8')
+        )
+        self.assertEqual(result, 'Hello, UTF-8 world!\n')
+
+    def test_read_text_given_encoding(self):
+        result = (
+            resources.files(self.data)
+            .joinpath('utf-16.file')
+            .read_text(encoding='utf-16')
+        )
+        self.assertEqual(result, 'Hello, UTF-16 world!\n')
+
+    def test_read_text_with_errors(self):
+        """
+        Raises UnicodeError without the 'errors' argument.
+        """
+        target = resources.files(self.data) / 'utf-16.file'
+        self.assertRaises(UnicodeError, target.read_text, encoding='utf-8')
+        result = target.read_text(encoding='utf-8', errors='ignore')
+        self.assertEqual(
+            result,
+            'H\x00e\x00l\x00l\x00o\x00,\x00 '
+            '\x00U\x00T\x00F\x00-\x001\x006\x00 '
+            '\x00w\x00o\x00r\x00l\x00d\x00!\x00\n\x00',
+        )
+
+
+class ReadDiskTests(ReadTests, unittest.TestCase):
+    data = data01
+
+
+class ReadZipTests(ReadTests, util.ZipSetup, unittest.TestCase):
+    def test_read_submodule_resource(self):
+        submodule = import_module('ziptestdata.subdirectory')
+        result = resources.files(submodule).joinpath('binary.file').read_bytes()
+        self.assertEqual(result, b'\0\1\2\3')
+
+    def test_read_submodule_resource_by_name(self):
+        result = (
+            resources.files('ziptestdata.subdirectory')
+            .joinpath('binary.file')
+            .read_bytes()
+        )
+        self.assertEqual(result, b'\0\1\2\3')
+
+
+class ReadNamespaceTests(ReadTests, unittest.TestCase):
+    def setUp(self):
+        from . import namespacedata01
+
+        self.data = namespacedata01
+
+
+if __name__ == '__main__':
+    unittest.main()

lib/importlib_resources/tests/test_reader.py

@@ -0,0 +1,144 @@
+import os.path
+import sys
+import pathlib
+import unittest
+
+from importlib import import_module
+from importlib_resources.readers import MultiplexedPath, NamespaceReader
+
+
+class MultiplexedPathTest(unittest.TestCase):
+    @classmethod
+    def setUpClass(cls):
+        path = pathlib.Path(__file__).parent / 'namespacedata01'
+        cls.folder = str(path)
+
+    def test_init_no_paths(self):
+        with self.assertRaises(FileNotFoundError):
+            MultiplexedPath()
+
+    def test_init_file(self):
+        with self.assertRaises(NotADirectoryError):
+            MultiplexedPath(os.path.join(self.folder, 'binary.file'))
+
+    def test_iterdir(self):
+        contents = {path.name for path in MultiplexedPath(self.folder).iterdir()}
+        try:
+            contents.remove('__pycache__')
+        except (KeyError, ValueError):
+            pass
+        self.assertEqual(contents, {'binary.file', 'utf-16.file', 'utf-8.file'})
+
+    def test_iterdir_duplicate(self):
+        data01 = os.path.abspath(os.path.join(__file__, '..', 'data01'))
+        contents = {
+            path.name for path in MultiplexedPath(self.folder, data01).iterdir()
+        }
+        for remove in ('__pycache__', '__init__.pyc'):
+            try:
+                contents.remove(remove)
+            except (KeyError, ValueError):
+                pass
+        self.assertEqual(
+            contents,
+            {'__init__.py', 'binary.file', 'subdirectory', 'utf-16.file', 'utf-8.file'},
+        )
+
+    def test_is_dir(self):
+        self.assertEqual(MultiplexedPath(self.folder).is_dir(), True)
+
+    def test_is_file(self):
+        self.assertEqual(MultiplexedPath(self.folder).is_file(), False)
+
+    def test_open_file(self):
+        path = MultiplexedPath(self.folder)
+        with self.assertRaises(FileNotFoundError):
+            path.read_bytes()
+        with self.assertRaises(FileNotFoundError):
+            path.read_text()
+        with self.assertRaises(FileNotFoundError):
+            path.open()
+
+    def test_join_path(self):
+        prefix = os.path.abspath(os.path.join(__file__, '..'))
+        data01 = os.path.join(prefix, 'data01')
+        path = MultiplexedPath(self.folder, data01)
+        self.assertEqual(
+            str(path.joinpath('binary.file'))[len(prefix) + 1 :],
+            os.path.join('namespacedata01', 'binary.file'),
+        )
+        self.assertEqual(
+            str(path.joinpath('subdirectory'))[len(prefix) + 1 :],
+            os.path.join('data01', 'subdirectory'),
+        )
+        self.assertEqual(
+            str(path.joinpath('imaginary'))[len(prefix) + 1 :],
+            os.path.join('namespacedata01', 'imaginary'),
+        )
+        self.assertEqual(path.joinpath(), path)
+
+    def test_join_path_compound(self):
+        path = MultiplexedPath(self.folder)
+        assert not path.joinpath('imaginary/foo.py').exists()
+
+    def test_join_path_common_subdir(self):
+        prefix = os.path.abspath(os.path.join(__file__, '..'))
+        data01 = os.path.join(prefix, 'data01')
+        data02 = os.path.join(prefix, 'data02')
+        path = MultiplexedPath(data01, data02)
+        self.assertIsInstance(path.joinpath('subdirectory'), MultiplexedPath)
+        self.assertEqual(
+            str(path.joinpath('subdirectory', 'subsubdir'))[len(prefix) + 1 :],
+            os.path.join('data02', 'subdirectory', 'subsubdir'),
+        )
+
+    def test_repr(self):
+        self.assertEqual(
+            repr(MultiplexedPath(self.folder)),
+            f"MultiplexedPath('{self.folder}')",
+        )
+
+    def test_name(self):
+        self.assertEqual(
+            MultiplexedPath(self.folder).name,
+            os.path.basename(self.folder),
+        )
+
+
+class NamespaceReaderTest(unittest.TestCase):
+    site_dir = str(pathlib.Path(__file__).parent)
+
+    @classmethod
+    def setUpClass(cls):
+        sys.path.append(cls.site_dir)
+
+    @classmethod
+    def tearDownClass(cls):
+        sys.path.remove(cls.site_dir)
+
+    def test_init_error(self):
+        with self.assertRaises(ValueError):
+            NamespaceReader(['path1', 'path2'])
+
+    def test_resource_path(self):
+        namespacedata01 = import_module('namespacedata01')
+        reader = NamespaceReader(namespacedata01.__spec__.submodule_search_locations)
+
+        root = os.path.abspath(os.path.join(__file__, '..', 'namespacedata01'))
+        self.assertEqual(
+            reader.resource_path('binary.file'), os.path.join(root, 'binary.file')
+        )
+        self.assertEqual(
+            reader.resource_path('imaginary'), os.path.join(root, 'imaginary')
+        )
+
+    def test_files(self):
+        namespacedata01 = import_module('namespacedata01')
+        reader = NamespaceReader(namespacedata01.__spec__.submodule_search_locations)
+        root = os.path.abspath(os.path.join(__file__, '..', 'namespacedata01'))
+        self.assertIsInstance(reader.files(), MultiplexedPath)
+        self.assertEqual(repr(reader.files()), f"MultiplexedPath('{root}')")
+
+
+if __name__ == '__main__':
+    unittest.main()

lib/importlib_resources/tests/test_resource.py

@@ -0,0 +1,252 @@
+import contextlib
+import sys
+import unittest
+import importlib_resources as resources
+import uuid
+import pathlib
+
+from . import data01
+from . import zipdata01, zipdata02
+from . import util
+from importlib import import_module
+from ._compat import import_helper, os_helper, unlink
+
+
+class ResourceTests:
+    # Subclasses are expected to set the `data` attribute.
+
+    def test_is_file_exists(self):
+        target = resources.files(self.data) / 'binary.file'
+        self.assertTrue(target.is_file())
+
+    def test_is_file_missing(self):
+        target = resources.files(self.data) / 'not-a-file'
+        self.assertFalse(target.is_file())
+
+    def test_is_dir(self):
+        target = resources.files(self.data) / 'subdirectory'
+        self.assertFalse(target.is_file())
+        self.assertTrue(target.is_dir())
+
+
+class ResourceDiskTests(ResourceTests, unittest.TestCase):
+    def setUp(self):
+        self.data = data01
+
+
+class ResourceZipTests(ResourceTests, util.ZipSetup, unittest.TestCase):
+    pass
+
+
+def names(traversable):
+    return {item.name for item in traversable.iterdir()}
+
+
+class ResourceLoaderTests(unittest.TestCase):
+    def test_resource_contents(self):
+        package = util.create_package(
+            file=data01, path=data01.__file__, contents=['A', 'B', 'C']
+        )
+        self.assertEqual(names(resources.files(package)), {'A', 'B', 'C'})
+
+    def test_is_file(self):
+        package = util.create_package(
+            file=data01, path=data01.__file__, contents=['A', 'B', 'C', 'D/E', 'D/F']
+        )
+        self.assertTrue(resources.files(package).joinpath('B').is_file())
+
+    def test_is_dir(self):
+        package = util.create_package(
+            file=data01, path=data01.__file__, contents=['A', 'B', 'C', 'D/E', 'D/F']
+        )
+        self.assertTrue(resources.files(package).joinpath('D').is_dir())
+
+    def test_resource_missing(self):
+        package = util.create_package(
+            file=data01, path=data01.__file__, contents=['A', 'B', 'C', 'D/E', 'D/F']
+        )
+        self.assertFalse(resources.files(package).joinpath('Z').is_file())
+
+
+class ResourceCornerCaseTests(unittest.TestCase):
+    def test_package_has_no_reader_fallback(self):
+        """
+        Test odd ball packages which:
+        # 1. Do not have a ResourceReader as a loader
+        # 2. Are not on the file system
+        # 3. Are not in a zip file
+        """
+        module = util.create_package(
+            file=data01, path=data01.__file__, contents=['A', 'B', 'C']
+        )
+        # Give the module a dummy loader.
+        module.__loader__ = object()
+        # Give the module a dummy origin.
+        module.__file__ = '/path/which/shall/not/be/named'
+        module.__spec__.loader = module.__loader__
+        module.__spec__.origin = module.__file__
+        self.assertFalse(resources.files(module).joinpath('A').is_file())
+
+
+class ResourceFromZipsTest01(util.ZipSetupBase, unittest.TestCase):
+    ZIP_MODULE = zipdata01  # type: ignore
+
+    def test_is_submodule_resource(self):
+        submodule = import_module('ziptestdata.subdirectory')
+        self.assertTrue(resources.files(submodule).joinpath('binary.file').is_file())
+
+    def test_read_submodule_resource_by_name(self):
+        self.assertTrue(
+            resources.files('ziptestdata.subdirectory')
+            .joinpath('binary.file')
+            .is_file()
+        )
+
+    def test_submodule_contents(self):
+        submodule = import_module('ziptestdata.subdirectory')
+        self.assertEqual(
+            names(resources.files(submodule)), {'__init__.py', 'binary.file'}
+        )
+
+    def test_submodule_contents_by_name(self):
+        self.assertEqual(
+            names(resources.files('ziptestdata.subdirectory')),
+            {'__init__.py', 'binary.file'},
+        )
+
+    def test_as_file_directory(self):
+        with resources.as_file(resources.files('ziptestdata')) as data:
+            assert data.name == 'ziptestdata'
+            assert data.is_dir()
+            assert data.joinpath('subdirectory').is_dir()
+            assert len(list(data.iterdir()))
+        assert not data.parent.exists()
+
+
+class ResourceFromZipsTest02(util.ZipSetupBase, unittest.TestCase):
+    ZIP_MODULE = zipdata02  # type: ignore
+
+    def test_unrelated_contents(self):
+        """
+        Test thata zip with two unrelated subpackages return
+        distinct resources. Ref python/importlib_resources#44.
+        """
+        self.assertEqual(
+            names(resources.files('ziptestdata.one')),
+            {'__init__.py', 'resource1.txt'},
+        )
+        self.assertEqual(
+            names(resources.files('ziptestdata.two')),
+            {'__init__.py', 'resource2.txt'},
+        )
+
+
+@contextlib.contextmanager
+def zip_on_path(dir):
+    data_path = pathlib.Path(zipdata01.__file__)
+    source_zip_path = data_path.parent.joinpath('ziptestdata.zip')
+    zip_path = pathlib.Path(dir) / f'{uuid.uuid4()}.zip'
+    zip_path.write_bytes(source_zip_path.read_bytes())
+    sys.path.append(str(zip_path))
+    import_module('ziptestdata')
+
+    try:
+        yield
+    finally:
+        with contextlib.suppress(ValueError):
+            sys.path.remove(str(zip_path))
+
+        with contextlib.suppress(KeyError):
+            del sys.path_importer_cache[str(zip_path)]
+            del sys.modules['ziptestdata']
+
+        with contextlib.suppress(OSError):
+            unlink(zip_path)
+
+
+class DeletingZipsTest(unittest.TestCase):
+    """Having accessed resources in a zip file should not keep an open
+    reference to the zip.
+    """
+
+    def setUp(self):
+        self.fixtures = contextlib.ExitStack()
+        self.addCleanup(self.fixtures.close)
+
+        modules = import_helper.modules_setup()
+        self.addCleanup(import_helper.modules_cleanup, *modules)
+
+        temp_dir = self.fixtures.enter_context(os_helper.temp_dir())
+        self.fixtures.enter_context(zip_on_path(temp_dir))
+
+    def test_iterdir_does_not_keep_open(self):
+        [item.name for item in resources.files('ziptestdata').iterdir()]
+
+    def test_is_file_does_not_keep_open(self):
+        resources.files('ziptestdata').joinpath('binary.file').is_file()
+
+    def test_is_file_failure_does_not_keep_open(self):
+        resources.files('ziptestdata').joinpath('not-present').is_file()
+
+    @unittest.skip("Desired but not supported.")
+    def test_as_file_does_not_keep_open(self):  # pragma: no cover
+        resources.as_file(resources.files('ziptestdata') / 'binary.file')
+
+    def test_entered_path_does_not_keep_open(self):
+        """
+        Mimic what certifi does on import to make its bundle
+        available for the process duration.
+        """
+        resources.as_file(resources.files('ziptestdata') / 'binary.file').__enter__()
+
+    def test_read_binary_does_not_keep_open(self):
+        resources.files('ziptestdata').joinpath('binary.file').read_bytes()
+
+    def test_read_text_does_not_keep_open(self):
+        resources.files('ziptestdata').joinpath('utf-8.file').read_text(
+            encoding='utf-8'
+        )
+
+
+class ResourceFromNamespaceTest01(unittest.TestCase):
+    site_dir = str(pathlib.Path(__file__).parent)
+
+    @classmethod
+    def setUpClass(cls):
+        sys.path.append(cls.site_dir)
+
+    @classmethod
+    def tearDownClass(cls):
+        sys.path.remove(cls.site_dir)
+
+    def test_is_submodule_resource(self):
+        self.assertTrue(
+            resources.files(import_module('namespacedata01'))
+            .joinpath('binary.file')
+            .is_file()
+        )
+
+    def test_read_submodule_resource_by_name(self):
+        self.assertTrue(
+            resources.files('namespacedata01').joinpath('binary.file').is_file()
+        )
+
+    def test_submodule_contents(self):
+        contents = names(resources.files(import_module('namespacedata01')))
+        try:
+            contents.remove('__pycache__')
+        except KeyError:
+            pass
+        self.assertEqual(contents, {'binary.file', 'utf-8.file', 'utf-16.file'})
+
+    def test_submodule_contents_by_name(self):
+        contents = names(resources.files('namespacedata01'))
+        try:
+            contents.remove('__pycache__')
+        except KeyError:
+            pass
+        self.assertEqual(contents, {'binary.file', 'utf-8.file', 'utf-16.file'})
+
+
+if __name__ == '__main__':
+    unittest.main()

lib/importlib_resources/tests/update-zips.py

@@ -0,0 +1,53 @@
+"""
+Generate the zip test data files.
+
+Run to build the tests/zipdataNN/ziptestdata.zip files from
+files in tests/dataNN.
+
+Replaces the file with the working copy, but does commit anything
+to the source repo.
+"""
+
+import contextlib
+import os
+import pathlib
+import zipfile
+
+
+def main():
+    """
+    >>> from unittest import mock
+    >>> monkeypatch = getfixture('monkeypatch')
+    >>> monkeypatch.setattr(zipfile, 'ZipFile', mock.MagicMock())
+    >>> print(); main()  # print workaround for bpo-32509
+    <BLANKLINE>
+    ...data01... -> ziptestdata/...
+    ...
+    ...data02... -> ziptestdata/...
+    ...
+    """
+    suffixes = '01', '02'
+    tuple(map(generate, suffixes))
+
+
+def generate(suffix):
+    root = pathlib.Path(__file__).parent.relative_to(os.getcwd())
+    zfpath = root / f'zipdata{suffix}/ziptestdata.zip'
+    with zipfile.ZipFile(zfpath, 'w') as zf:
+        for src, rel in walk(root / f'data{suffix}'):
+            dst = 'ziptestdata' / pathlib.PurePosixPath(rel.as_posix())
+            print(src, '->', dst)
+            zf.write(src, dst)
+
+
+def walk(datapath):
+    for dirpath, dirnames, filenames in os.walk(datapath):
+        with contextlib.suppress(ValueError):
+            dirnames.remove('__pycache__')
+        for filename in filenames:
+            res = pathlib.Path(dirpath) / filename
+            rel = res.relative_to(datapath)
+            yield res, rel
+
+
+__name__ == '__main__' and main()

lib/importlib_resources/tests/util.py

@@ -0,0 +1,179 @@
+import abc
+import importlib
+import io
+import sys
+import types
+import pathlib
+
+from . import data01
+from . import zipdata01
+from ..abc import ResourceReader
+from ._compat import import_helper
+
+
+from importlib.machinery import ModuleSpec
+
+
+class Reader(ResourceReader):
+    def __init__(self, **kwargs):
+        vars(self).update(kwargs)
+
+    def get_resource_reader(self, package):
+        return self
+
+    def open_resource(self, path):
+        self._path = path
+        if isinstance(self.file, Exception):
+            raise self.file
+        return self.file
+
+    def resource_path(self, path_):
+        self._path = path_
+        if isinstance(self.path, Exception):
+            raise self.path
+        return self.path
+
+    def is_resource(self, path_):
+        self._path = path_
+        if isinstance(self.path, Exception):
+            raise self.path
+
+        def part(entry):
+            return entry.split('/')
+
+        return any(
+            len(parts) == 1 and parts[0] == path_ for parts in map(part, self._contents)
+        )
+
+    def contents(self):
+        if isinstance(self.path, Exception):
+            raise self.path
+        yield from self._contents
+
+
+def create_package_from_loader(loader, is_package=True):
+    name = 'testingpackage'
+    module = types.ModuleType(name)
+    spec = ModuleSpec(name, loader, origin='does-not-exist', is_package=is_package)
+    module.__spec__ = spec
+    module.__loader__ = loader
+    return module
+
+
+def create_package(file=None, path=None, is_package=True, contents=()):
+    return create_package_from_loader(
+        Reader(file=file, path=path, _contents=contents),
+        is_package,
+    )
+
+
+class CommonTests(metaclass=abc.ABCMeta):
+    """
+    Tests shared by test_open, test_path, and test_read.
+    """
+
+    @abc.abstractmethod
+    def execute(self, package, path):
+        """
+        Call the pertinent legacy API function (e.g. open_text, path)
+        on package and path.
+        """
+
+    def test_package_name(self):
+        """
+        Passing in the package name should succeed.
+        """
+        self.execute(data01.__name__, 'utf-8.file')
+
+    def test_package_object(self):
+        """
+        Passing in the package itself should succeed.
+        """
+        self.execute(data01, 'utf-8.file')
+
+    def test_string_path(self):
+        """
+        Passing in a string for the path should succeed.
+        """
+        path = 'utf-8.file'
+        self.execute(data01, path)
+
+    def test_pathlib_path(self):
+        """
+        Passing in a pathlib.PurePath object for the path should succeed.
+        """
+        path = pathlib.PurePath('utf-8.file')
+        self.execute(data01, path)
+
+    def test_importing_module_as_side_effect(self):
+        """
+        The anchor package can already be imported.
+        """
+        del sys.modules[data01.__name__]
+        self.execute(data01.__name__, 'utf-8.file')
+
+    def test_missing_path(self):
+        """
+        Attempting to open or read or request the path for a
+        non-existent path should succeed if open_resource
+        can return a viable data stream.
+        """
+        bytes_data = io.BytesIO(b'Hello, world!')
+        package = create_package(file=bytes_data, path=FileNotFoundError())
+        self.execute(package, 'utf-8.file')
+        self.assertEqual(package.__loader__._path, 'utf-8.file')
+
+    def test_extant_path(self):
+        # Attempting to open or read or request the path when the
+        # path does exist should still succeed. Does not assert
+        # anything about the result.
+        bytes_data = io.BytesIO(b'Hello, world!')
+        # any path that exists
+        path = __file__
+        package = create_package(file=bytes_data, path=path)
+        self.execute(package, 'utf-8.file')
+        self.assertEqual(package.__loader__._path, 'utf-8.file')
+
+    def test_useless_loader(self):
+        package = create_package(file=FileNotFoundError(), path=FileNotFoundError())
+        with self.assertRaises(FileNotFoundError):
+            self.execute(package, 'utf-8.file')
+
+
+class ZipSetupBase:
+    ZIP_MODULE = None
+
+    @classmethod
+    def setUpClass(cls):
+        data_path = pathlib.Path(cls.ZIP_MODULE.__file__)
+        data_dir = data_path.parent
+        cls._zip_path = str(data_dir / 'ziptestdata.zip')
+        sys.path.append(cls._zip_path)
+        cls.data = importlib.import_module('ziptestdata')
+
+    @classmethod
+    def tearDownClass(cls):
+        try:
+            sys.path.remove(cls._zip_path)
+        except ValueError:
+            pass
+
+        try:
+            del sys.path_importer_cache[cls._zip_path]
+            del sys.modules[cls.data.__name__]
+        except KeyError:
+            pass
+
+        try:
+            del cls.data
+            del cls._zip_path
+        except AttributeError:
+            pass
+
+    def setUp(self):
+        modules = import_helper.modules_setup()
+        self.addCleanup(import_helper.modules_cleanup, *modules)
+
+
+class ZipSetup(ZipSetupBase):
+    ZIP_MODULE = zipdata01  # type: ignore