bpo-39791 native hooks for importlib.resources.files (GH-20576)

* Provide native .files support on SourceFileLoader.

* Add native importlib.resources.files() support to zipimporter. Remove fallback support.

* make regen-all

* 📜🤖 Added by blurb_it.

* Move 'files' into the ResourceReader so it can carry the relevant module name context.

* Create 'importlib.readers' module and add FileReader to it.

* Add zip reader and rely on it for a TraversableResources object on zipimporter.

* Remove TraversableAdapter, no longer needed.

* Update blurb.

* Replace backslashes with forward slashes.

* Incorporate changes from importlib_metadata 2.0, finalizing the interface for extension via get_resource_reader.

Co-authored-by: blurb-it[bot] <43283697+blurb-it[bot]@users.noreply.github.com>

5 files changed, 110 insertions, 115 deletions

diff --git a/Lib/importlib/_bootstrap_external.py b/Lib/importlib/_bootstrap_external.py
index 25a3f8c..4f06039 100644
--- a/Lib/importlib/_bootstrap_external.py
+++ b/Lib/importlib/_bootstrap_external.py
@@ -982,32 +982,10 @@ class FileLoader:
             with _io.FileIO(path, 'r') as file:
                 return file.read()
 
-    # ResourceReader ABC API.
-
     @_check_name
     def get_resource_reader(self, module):
-        if self.is_package(module):
-            return self
-        return None
-
-    def open_resource(self, resource):
-        path = _path_join(_path_split(self.path)[0], resource)
-        return _io.FileIO(path, 'r')
-
-    def resource_path(self, resource):
-        if not self.is_resource(resource):
-            raise FileNotFoundError
-        path = _path_join(_path_split(self.path)[0], resource)
-        return path
-
-    def is_resource(self, name):
-        if path_sep in name:
-            return False
-        path = _path_join(_path_split(self.path)[0], name)
-        return _path_isfile(path)
-
-    def contents(self):
-        return iter(_os.listdir(_path_split(self.path)[0]))
+        from importlib.readers import FileReader
+        return FileReader(self)
 
 
 class SourceFileLoader(FileLoader, SourceLoader):
diff --git a/Lib/importlib/_common.py b/Lib/importlib/_common.py
index ba7cbac..b15c59e 100644
--- a/Lib/importlib/_common.py
+++ b/Lib/importlib/_common.py
@@ -1,38 +1,82 @@
 import os
 import pathlib
-import zipfile
 import tempfile
 import functools
 import contextlib
+import types
+import importlib
 
+from typing import Union, Any, Optional
+from .abc import ResourceReader
 
-def from_package(package):
+Package = Union[types.ModuleType, str]
+
+
+def files(package):
     """
-    Return a Traversable object for the given package.
+    Get a Traversable resource from a package
+    """
+    return from_package(get_package(package))
+
 
+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.
     """
-    spec = package.__spec__
-    return from_traversable_resources(spec) or fallback_resources(spec)
+    str_path = str(path)
+    parent, file_name = os.path.split(str_path)
+    if parent:
+        raise ValueError('{!r} must be only a file name'.format(path))
+    return file_name
 
 
-def from_traversable_resources(spec):
+def get_resource_reader(package):
+    # type: (types.ModuleType) -> Optional[ResourceReader]
     """
-    If the spec.loader implements TraversableResources,
-    directly or implicitly, it will have a ``files()`` method.
+    Return the package's loader if it's a ResourceReader.
     """
-    with contextlib.suppress(AttributeError):
-        return spec.loader.files()
+    # 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)
+    if reader is None:
+        return None
+    return reader(spec.name)
 
 
-def fallback_resources(spec):
-    package_directory = pathlib.Path(spec.origin).parent
-    try:
-        archive_path = spec.loader.archive
-        rel_path = package_directory.relative_to(archive_path)
-        return zipfile.Path(archive_path, str(rel_path) + '/')
-    except Exception:
-        pass
-    return package_directory
+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 resolved.__spec__.submodule_search_locations is None:
+        raise TypeError('{!r} is not a package'.format(package))
+    return resolved
+
+
+def from_package(package):
+    """
+    Return a Traversable object for the given package.
+
+    """
+    spec = package.__spec__
+    reader = spec.loader.get_resource_reader(spec.name)
+    return reader.files()
 
 
 @contextlib.contextmanager
diff --git a/Lib/importlib/abc.py b/Lib/importlib/abc.py
index b8a9bb1..0b20e7c 100644
--- a/Lib/importlib/abc.py
+++ b/Lib/importlib/abc.py
@@ -468,7 +468,7 @@ class TraversableResources(ResourceReader):
         raise FileNotFoundError(resource)
 
     def is_resource(self, path):
-        return self.files().joinpath(path).isfile()
+        return self.files().joinpath(path).is_file()
 
     def contents(self):
         return (item.name for item in self.files().iterdir())
diff --git a/Lib/importlib/readers.py b/Lib/importlib/readers.py
new file mode 100644
index 0000000..fb49ebe
--- /dev/null
+++ b/Lib/importlib/readers.py
@@ -0,0 +1,30 @@
+import zipfile
+import pathlib
+from . import abc
+
+
+class FileReader(abc.TraversableResources):
+    def __init__(self, loader):
+        self.path = pathlib.Path(loader.path).parent
+
+    def files(self):
+        return self.path
+
+
+class ZipReader(FileReader):
+    def __init__(self, loader, module):
+        _, _, name = module.rpartition('.')
+        prefix = loader.prefix.replace('\\', '/') + name + '/'
+        self.path = zipfile.Path(loader.archive, prefix)
+
+    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()
diff --git a/Lib/importlib/resources.py b/Lib/importlib/resources.py
index b803a01..4535619 100644
--- a/Lib/importlib/resources.py
+++ b/Lib/importlib/resources.py
@@ -1,15 +1,13 @@
 import os
 
-from . import abc as resources_abc
 from . import _common
-from ._common import as_file
+from ._common import as_file, files
 from contextlib import contextmanager, suppress
-from importlib import import_module
 from importlib.abc import ResourceLoader
 from io import BytesIO, TextIOWrapper
 from pathlib import Path
 from types import ModuleType
-from typing import ContextManager, Iterable, Optional, Union
+from typing import ContextManager, Iterable, Union
 from typing import cast
 from typing.io import BinaryIO, TextIO
 
@@ -33,60 +31,11 @@ Package = Union[str, ModuleType]
 Resource = Union[str, os.PathLike]
 
 
-def _resolve(name) -> ModuleType:
-    """If name is a string, resolve to a module."""
-    if hasattr(name, '__spec__'):
-        return name
-    return import_module(name)
-
-
-def _get_package(package) -> ModuleType:
-    """Take a package name or module object and return the module.
-
-    If a name, the module is imported.  If the resolved module
-    object is not a package, raise an exception.
-    """
-    module = _resolve(package)
-    if module.__spec__.submodule_search_locations is None:
-        raise TypeError('{!r} is not a package'.format(package))
-    return module
-
-
-def _normalize_path(path) -> str:
-    """Normalize a path by ensuring it is a string.
-
-    If the resulting string contains path separators, an exception is raised.
-    """
-    parent, file_name = os.path.split(path)
-    if parent:
-        raise ValueError('{!r} must be only a file name'.format(path))
-    return file_name
-
-
-def _get_resource_reader(
-        package: ModuleType) -> Optional[resources_abc.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__
-    if hasattr(spec.loader, 'get_resource_reader'):
-        return cast(resources_abc.ResourceReader,
-                    spec.loader.get_resource_reader(spec.name))
-    return None
-
-
-def _check_location(package):
-    if package.__spec__.origin is None or not package.__spec__.has_location:
-        raise FileNotFoundError(f'Package has no location {package!r}')
-
-
 def open_binary(package: Package, resource: Resource) -> BinaryIO:
     """Return a file-like object opened for binary reading of the resource."""
-    resource = _normalize_path(resource)
-    package = _get_package(package)
-    reader = _get_resource_reader(package)
+    resource = _common.normalize_path(resource)
+    package = _common.get_package(package)
+    reader = _common.get_resource_reader(package)
     if reader is not None:
         return reader.open_resource(resource)
     absolute_package_path = os.path.abspath(
@@ -140,13 +89,6 @@ def read_text(package: Package,
         return fp.read()
 
 
-def files(package: Package) -> resources_abc.Traversable:
-    """
-    Get a Traversable resource from a package
-    """
-    return _common.from_package(_get_package(package))
-
-
 def path(
         package: Package, resource: Resource,
         ) -> 'ContextManager[Path]':
@@ -158,17 +100,18 @@ def path(
     raised if the file was deleted prior to the context manager
     exiting).
     """
-    reader = _get_resource_reader(_get_package(package))
+    reader = _common.get_resource_reader(_common.get_package(package))
     return (
         _path_from_reader(reader, resource)
         if reader else
-        _common.as_file(files(package).joinpath(_normalize_path(resource)))
+        _common.as_file(
+            _common.files(package).joinpath(_common.normalize_path(resource)))
         )
 
 
 @contextmanager
 def _path_from_reader(reader, resource):
-    norm_resource = _normalize_path(resource)
+    norm_resource = _common.normalize_path(resource)
     with suppress(FileNotFoundError):
         yield Path(reader.resource_path(norm_resource))
         return
@@ -182,9 +125,9 @@ def is_resource(package: Package, name: str) -> bool:
 
     Directories are *not* resources.
     """
-    package = _get_package(package)
-    _normalize_path(name)
-    reader = _get_resource_reader(package)
+    package = _common.get_package(package)
+    _common.normalize_path(name)
+    reader = _common.get_resource_reader(package)
     if reader is not None:
         return reader.is_resource(name)
     package_contents = set(contents(package))
@@ -200,8 +143,8 @@ def contents(package: Package) -> Iterable[str]:
     not considered resources.  Use `is_resource()` on each entry returned here
     to check if it is a resource or not.
     """
-    package = _get_package(package)
-    reader = _get_resource_reader(package)
+    package = _common.get_package(package)
+    reader = _common.get_resource_reader(package)
     if reader is not None:
         return reader.contents()
     # Is the package a namespace package?  By definition, namespace packages