8 files changed, 840 insertions, 0 deletions
diff --git a/Lib/importlib/resources/__init__.py b/Lib/importlib/resources/__init__.py
new file mode 100644
index 00000000000..34e3a9950cc
--- /dev/null
+++ b/Lib/importlib/resources/__init__.py
@@ -0,0 +1,36 @@
+"""Read resources contained within a package."""
+
+from ._common import (
+    as_file,
+    files,
+    Package,
+)
+
+from ._legacy import (
+    contents,
+    open_binary,
+    read_binary,
+    open_text,
+    read_text,
+    is_resource,
+    path,
+    Resource,
+)
+
+from .abc import ResourceReader
+
+
+__all__ = [
+    'Package',
+    'Resource',
+    'ResourceReader',
+    'as_file',
+    'contents',
+    'files',
+    'is_resource',
+    'open_binary',
+    'open_text',
+    'path',
+    'read_binary',
+    'read_text',
+]
diff --git a/Lib/importlib/resources/_adapters.py b/Lib/importlib/resources/_adapters.py
new file mode 100644
index 00000000000..ea363d86a56
--- /dev/null
+++ b/Lib/importlib/resources/_adapters.py
@@ -0,0 +1,170 @@
+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(
+        "Invalid mode value '{}', only 'r' and 'rb' are supported".format(mode)
+    )
+
+
+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)
diff --git a/Lib/importlib/resources/_common.py b/Lib/importlib/resources/_common.py
new file mode 100644
index 00000000000..147ea19188f
--- /dev/null
+++ b/Lib/importlib/resources/_common.py
@@ -0,0 +1,104 @@
+import os
+import pathlib
+import tempfile
+import functools
+import contextlib
+import types
+import importlib
+
+from typing import Union, Optional
+from .abc import ResourceReader, Traversable
+
+from ._adapters import wrap_spec
+
+Package = Union[types.ModuleType, str]
+
+
+def files(package):
+    # type: (Package) -> Traversable
+    """
+    Get a Traversable resource from a package
+    """
+    return from_package(get_package(package))
+
+
+def get_resource_reader(package):
+    # type: (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
+
+
+def resolve(cand):
+    # type: (Package) -> types.ModuleType
+    return cand if isinstance(cand, types.ModuleType) else importlib.import_module(cand)
+
+
+def get_package(package):
+    # type: (Package) -> types.ModuleType
+    """Take a package name or module object and return the module.
+
+    Raise an exception if the resolved module is not a package.
+    """
+    resolved = resolve(package)
+    if wrap_spec(resolved).submodule_search_locations is None:
+        raise TypeError(f'{package!r} is not a package')
+    return resolved
+
+
+def from_package(package):
+    """
+    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=''):
+    # 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
+
+
+@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 _tempfile(path.read_bytes, suffix=path.name)
+
+
+@as_file.register(pathlib.Path)
+@contextlib.contextmanager
+def _(path):
+    """
+    Degenerate behavior for pathlib.Path objects.
+    """
+    yield path
diff --git a/Lib/importlib/resources/_itertools.py b/Lib/importlib/resources/_itertools.py
new file mode 100644
index 00000000000..cce05582ffc
--- /dev/null
+++ b/Lib/importlib/resources/_itertools.py
@@ -0,0 +1,35 @@
+from itertools import filterfalse
+
+from typing import (
+    Callable,
+    Iterable,
+    Iterator,
+    Optional,
+    Set,
+    TypeVar,
+    Union,
+)
+
+# Type and type variable definitions
+_T = TypeVar('_T')
+_U = TypeVar('_U')
+
+
+def unique_everseen(
+    iterable: Iterable[_T], key: Optional[Callable[[_T], _U]] = None
+) -> Iterator[_T]:
+    "List unique elements, preserving order. Remember all elements ever seen."
+    # unique_everseen('AAAABBBCCDAABBB') --> A B C D
+    # unique_everseen('ABBCcAD', str.lower) --> A B C D
+    seen: Set[Union[_T, _U]] = set()
+    seen_add = seen.add
+    if key is None:
+        for element in filterfalse(seen.__contains__, iterable):
+            seen_add(element)
+            yield element
+    else:
+        for element in iterable:
+            k = key(element)
+            if k not in seen:
+                seen_add(k)
+                yield element
diff --git a/Lib/importlib/resources/_legacy.py b/Lib/importlib/resources/_legacy.py
new file mode 100644
index 00000000000..1d5d3f1fbb1
--- /dev/null
+++ b/Lib/importlib/resources/_legacy.py
@@ -0,0 +1,121 @@
+import functools
+import os
+import pathlib
+import types
+import warnings
+
+from typing import Union, Iterable, ContextManager, BinaryIO, TextIO, Any
+
+from . import _common
+
+Package = Union[types.ModuleType, str]
+Resource = str
+
+
+def deprecated(func):
+    @functools.wraps(func)
+    def wrapper(*args, **kwargs):
+        warnings.warn(
+            f"{func.__name__} is deprecated. Use files() instead. "
+            "Refer to https://importlib-resources.readthedocs.io"
+            "/en/latest/using.html#migrating-from-legacy for migration advice.",
+            DeprecationWarning,
+            stacklevel=2,
+        )
+        return func(*args, **kwargs)
+
+    return wrapper
+
+
+def normalize_path(path):
+    # type: (Any) -> str
+    """Normalize a path by ensuring it is a string.
+
+    If the resulting string contains path separators, an exception is raised.
+    """
+    str_path = str(path)
+    parent, file_name = os.path.split(str_path)
+    if parent:
+        raise ValueError(f'{path!r} must be only a file name')
+    return file_name
+
+
+@deprecated
+def open_binary(package: Package, resource: Resource) -> BinaryIO:
+    """Return a file-like object opened for binary reading of the resource."""
+    return (_common.files(package) / normalize_path(resource)).open('rb')
+
+
+@deprecated
+def read_binary(package: Package, resource: Resource) -> bytes:
+    """Return the binary contents of the resource."""
+    return (_common.files(package) / normalize_path(resource)).read_bytes()
+
+
+@deprecated
+def open_text(
+    package: Package,
+    resource: Resource,
+    encoding: str = 'utf-8',
+    errors: str = 'strict',
+) -> TextIO:
+    """Return a file-like object opened for text reading of the resource."""
+    return (_common.files(package) / normalize_path(resource)).open(
+        'r', encoding=encoding, errors=errors
+    )
+
+
+@deprecated
+def read_text(
+    package: Package,
+    resource: Resource,
+    encoding: str = 'utf-8',
+    errors: str = 'strict',
+) -> str:
+    """Return the decoded string of the resource.
+
+    The decoding-related arguments have the same semantics as those of
+    bytes.decode().
+    """
+    with open_text(package, resource, encoding, errors) as fp:
+        return fp.read()
+
+
+@deprecated
+def contents(package: Package) -> Iterable[str]:
+    """Return an iterable of entries in `package`.
+
+    Note that not all entries are resources.  Specifically, directories are
+    not considered resources.  Use `is_resource()` on each entry returned here
+    to check if it is a resource or not.
+    """
+    return [path.name for path in _common.files(package).iterdir()]
+
+
+@deprecated
+def is_resource(package: Package, name: str) -> bool:
+    """True if `name` is a resource inside `package`.
+
+    Directories are *not* resources.
+    """
+    resource = normalize_path(name)
+    return any(
+        traversable.name == resource and traversable.is_file()
+        for traversable in _common.files(package).iterdir()
+    )
+
+
+@deprecated
+def path(
+    package: Package,
+    resource: Resource,
+) -> ContextManager[pathlib.Path]:
+    """A context manager providing a file path object to the resource.
+
+    If the resource does not already exist on its own on the file system,
+    a temporary file will be created. If the file was created, the file
+    will be deleted upon exiting the context manager (no exception is
+    raised if the file was deleted prior to the context manager
+    exiting).
+    """
+    return _common.as_file(_common.files(package) / normalize_path(resource))
diff --git a/Lib/importlib/resources/abc.py b/Lib/importlib/resources/abc.py
new file mode 100644
index 00000000000..e9efdab5ea8
--- /dev/null
+++ b/Lib/importlib/resources/abc.py
@@ -0,0 +1,136 @@
+import abc
+from typing import BinaryIO, Iterable, Text
+from typing import runtime_checkable, Protocol
+
+
+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
+
+
+@runtime_checkable
+class Traversable(Protocol):
+    """
+    An object with a subset of pathlib.Path methods suitable for
+    traversing directories and opening files.
+    """
+
+    @abc.abstractmethod
+    def iterdir(self):
+        """
+        Yield Traversable objects in self
+        """
+
+    def read_bytes(self):
+        """
+        Read contents of self as bytes
+        """
+        with self.open('rb') as strm:
+            return strm.read()
+
+    def read_text(self, encoding=None):
+        """
+        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
+        """
+
+    @abc.abstractmethod
+    def joinpath(self, child):
+        """
+        Return Traversable child in self
+        """
+
+    def __truediv__(self, child):
+        """
+        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.
+        """
+
+    @abc.abstractproperty
+    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):
+        """Return a Traversable object for the loaded package."""
+
+    def open_resource(self, resource):
+        return self.files().joinpath(resource).open('rb')
+
+    def resource_path(self, resource):
+        raise FileNotFoundError(resource)
+
+    def is_resource(self, path):
+        return self.files().joinpath(path).is_file()
+
+    def contents(self):
+        return (item.name for item in self.files().iterdir())
diff --git a/Lib/importlib/resources/readers.py b/Lib/importlib/resources/readers.py
new file mode 100644
index 00000000000..b470a2062b2
--- /dev/null
+++ b/Lib/importlib/resources/readers.py
@@ -0,0 +1,122 @@
+import collections
+import operator
+import pathlib
+import zipfile
+
+from . import abc
+
+from ._itertools import unique_everseen
+
+
+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 zipfile.Path(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):
+        files = (file for path in self._paths for file in path.iterdir())
+        return unique_everseen(files, key=operator.attrgetter('name'))
+
+    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, child):
+        # first try to find child in current paths
+        for file in self.iterdir():
+            if file.name == child:
+                return file
+        # if it does not exist, construct it with the first path
+        return self._paths[0] / child
+
+    __truediv__ = joinpath
+
+    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
diff --git a/Lib/importlib/resources/simple.py b/Lib/importlib/resources/simple.py
new file mode 100644
index 00000000000..da073cbdb11
--- /dev/null
+++ b/Lib/importlib/resources/simple.py
@@ -0,0 +1,116 @@
+"""
+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.
+    """
+
+    @abc.abstractproperty
+    def package(self):
+        # type: () -> str
+        """
+        The name of the package for which this reader loads resources.
+        """
+
+    @abc.abstractmethod
+    def children(self):
+        # type: () -> List['SimpleReader']
+        """
+        Obtain an iterable of SimpleReader for available
+        child containers (e.g. directories).
+        """
+
+    @abc.abstractmethod
+    def resources(self):
+        # type: () -> List[str]
+        """
+        Obtain available named resources for this virtual package.
+        """
+
+    @abc.abstractmethod
+    def open_binary(self, resource):
+        # type: (str) -> BinaryIO
+        """
+        Obtain a File-like for a named resource.
+        """
+
+    @property
+    def name(self):
+        return self.package.split('.')[-1]
+
+
+class ResourceHandle(Traversable):
+    """
+    Handle to a named resource in a ResourceReader.
+    """
+
+    def __init__(self, parent, name):
+        # type: (ResourceContainer, str) -> None
+        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 ResourceContainer(Traversable):
+    """
+    Traversable container for a package's resources via its reader.
+    """
+
+    def __init__(self, reader):
+        # type: (SimpleReader) -> None
+        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()
+
+    def joinpath(self, name):
+        return next(
+            traversable for traversable in self.iterdir() if traversable.name == name
+        )
+
+
+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)