gh-97930: Apply changes from importlib_resources 5.12. (GH-102010)

14 files changed, 237 insertions, 127 deletions

diff --git a/Lib/importlib/resources/_adapters.py b/Lib/importlib/resources/_adapters.py
index f22f6bc..50688fb 100644
--- a/Lib/importlib/resources/_adapters.py
+++ b/Lib/importlib/resources/_adapters.py
@@ -34,9 +34,7 @@ def _io_wrapper(file, mode='r', *args, **kwargs):
         return TextIOWrapper(file, *args, **kwargs)
     elif mode == 'rb':
         return file
-    raise ValueError(
-        f"Invalid mode value '{mode}', only 'r' and 'rb' are supported"
-    )
+    raise ValueError(f"Invalid mode value '{mode}', only 'r' and 'rb' are supported")
 
 
 class CompatibilityFiles:
diff --git a/Lib/importlib/resources/_itertools.py b/Lib/importlib/resources/_itertools.py
index cce0558..7b775ef5a 100644
--- a/Lib/importlib/resources/_itertools.py
+++ b/Lib/importlib/resources/_itertools.py
@@ -1,35 +1,38 @@
-from itertools import filterfalse
+# 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)
 
-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
+    try:
+        second_value = next(it)
+    except StopIteration:
+        pass
     else:
-        for element in iterable:
-            k = key(element)
-            if k not in seen:
-                seen_add(k)
-                yield element
+        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
diff --git a/Lib/importlib/resources/readers.py b/Lib/importlib/resources/readers.py
index 80cb320..c3cdf76 100644
--- a/Lib/importlib/resources/readers.py
+++ b/Lib/importlib/resources/readers.py
@@ -1,11 +1,12 @@
 import collections
-import operator
+import itertools
 import pathlib
+import operator
 import zipfile
 
 from . import abc
 
-from ._itertools import unique_everseen
+from ._itertools import only
 
 
 def remove_duplicates(items):
@@ -41,8 +42,10 @@ class ZipReader(abc.TraversableResources):
             raise FileNotFoundError(exc.args[0])
 
     def is_resource(self, path):
-        # workaround for `zipfile.Path.is_file` returning true
-        # for non-existent paths.
+        """
+        Workaround for `zipfile.Path.is_file` returning true
+        for non-existent paths.
+        """
         target = self.files().joinpath(path)
         return target.is_file() and target.exists()
 
@@ -67,8 +70,10 @@ class MultiplexedPath(abc.Traversable):
             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'))
+        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')
@@ -90,6 +95,25 @@ class MultiplexedPath(abc.Traversable):
             # 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')
 
diff --git a/Lib/test/test_importlib/resources/_path.py b/Lib/test/test_importlib/resources/_path.py
index c630e4d..1f97c96 100644
--- a/Lib/test/test_importlib/resources/_path.py
+++ b/Lib/test/test_importlib/resources/_path.py
@@ -1,12 +1,16 @@
 import pathlib
 import functools
 
+from typing import Dict, Union
+
 
 ####
-# from jaraco.path 3.4
+# from jaraco.path 3.4.1
+
+FilesSpec = Dict[str, Union[str, bytes, 'FilesSpec']]  # type: ignore
 
 
-def build(spec, prefix=pathlib.Path()):
+def build(spec: FilesSpec, prefix=pathlib.Path()):
     """
     Build a set of files/directories, as described by the spec.
 
@@ -23,15 +27,17 @@ def build(spec, prefix=pathlib.Path()):
     ...         "baz.py": "# Some code",
     ...     }
     ... }
-    >>> tmpdir = getfixture('tmpdir')
-    >>> build(spec, tmpdir)
+    >>> 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, path):
+def create(content: Union[str, bytes, FilesSpec], path):
     path.mkdir(exist_ok=True)
     build(content, prefix=path)  # type: ignore
 
@@ -43,7 +49,7 @@ def _(content: bytes, path):
 
 @create.register
 def _(content: str, path):
-    path.write_text(content)
+    path.write_text(content, encoding='utf-8')
 
 
 # end from jaraco.path
diff --git a/Lib/test/test_importlib/resources/data02/subdirectory/subsubdir/resource.txt b/Lib/test/test_importlib/resources/data02/subdirectory/subsubdir/resource.txt
new file mode 100644
index 0000000..48f587a
--- /dev/null
+++ b/Lib/test/test_importlib/resources/data02/subdirectory/subsubdir/resource.txt
@@ -0,0 +1 @@
+a resource
\ No newline at end of file
diff --git a/Lib/test/test_importlib/resources/test_compatibilty_files.py b/Lib/test/test_importlib/resources/test_compatibilty_files.py
index 6fa18a2..bcf608d 100644
--- a/Lib/test/test_importlib/resources/test_compatibilty_files.py
+++ b/Lib/test/test_importlib/resources/test_compatibilty_files.py
@@ -64,11 +64,13 @@ class CompatibilityFilesTests(unittest.TestCase):
 
     def test_spec_path_open(self):
         self.assertEqual(self.files.read_bytes(), b'Hello, world!')
-        self.assertEqual(self.files.read_text(), '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(), 'Hello, world!')
+        self.assertEqual(
+            (self.files / 'a').read_text(encoding='utf-8'), 'Hello, world!'
+        )
 
     def test_orphan_path_open(self):
         with self.assertRaises(FileNotFoundError):
diff --git a/Lib/test/test_importlib/resources/test_custom.py b/Lib/test/test_importlib/resources/test_custom.py
new file mode 100644
index 0000000..7312720
--- /dev/null
+++ b/Lib/test/test_importlib/resources/test_custom.py
@@ -0,0 +1,46 @@
+import unittest
+import contextlib
+import pathlib
+
+from test.support import os_helper
+
+from importlib import resources
+from importlib.resources.abc import TraversableResources, ResourceReader
+from . import util
+
+
+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
diff --git a/Lib/test/test_importlib/resources/test_files.py b/Lib/test/test_importlib/resources/test_files.py
index fe813ae..1450cfb 100644
--- a/Lib/test/test_importlib/resources/test_files.py
+++ b/Lib/test/test_importlib/resources/test_files.py
@@ -85,7 +85,7 @@ class ModulesFilesTests(SiteDir, unittest.TestCase):
         _path.build(spec, self.site_dir)
         import mod
 
-        actual = resources.files(mod).joinpath('res.txt').read_text()
+        actual = resources.files(mod).joinpath('res.txt').read_text(encoding='utf-8')
         assert actual == spec['res.txt']
 
 
@@ -99,7 +99,7 @@ class ImplicitContextFilesTests(SiteDir, unittest.TestCase):
                 '__init__.py': textwrap.dedent(
                     """
                     import importlib.resources as res
-                    val = res.files().joinpath('res.txt').read_text()
+                    val = res.files().joinpath('res.txt').read_text(encoding='utf-8')
                     """
                 ),
                 'res.txt': 'resources are the best',
diff --git a/Lib/test/test_importlib/resources/test_open.py b/Lib/test/test_importlib/resources/test_open.py
index 0554c41..86becb4 100644
--- a/Lib/test/test_importlib/resources/test_open.py
+++ b/Lib/test/test_importlib/resources/test_open.py
@@ -15,7 +15,7 @@ class CommonBinaryTests(util.CommonTests, unittest.TestCase):
 class CommonTextTests(util.CommonTests, unittest.TestCase):
     def execute(self, package, path):
         target = resources.files(package).joinpath(path)
-        with target.open():
+        with target.open(encoding='utf-8'):
             pass
 
 
@@ -28,7 +28,7 @@ class OpenTests:
 
     def test_open_text_default_encoding(self):
         target = resources.files(self.data) / 'utf-8.file'
-        with target.open() as fp:
+        with target.open(encoding='utf-8') as fp:
             result = fp.read()
             self.assertEqual(result, 'Hello, UTF-8 world!\n')
 
@@ -39,7 +39,9 @@ class OpenTests:
         self.assertEqual(result, 'Hello, UTF-16 world!\n')
 
     def test_open_text_with_errors(self):
-        # Raises UnicodeError without the 'errors' argument.
+        """
+        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)
@@ -54,11 +56,13 @@ class OpenTests:
 
     def test_open_binary_FileNotFoundError(self):
         target = resources.files(self.data) / 'does-not-exist'
-        self.assertRaises(FileNotFoundError, target.open, 'rb')
+        with self.assertRaises(FileNotFoundError):
+            target.open('rb')
 
     def test_open_text_FileNotFoundError(self):
         target = resources.files(self.data) / 'does-not-exist'
-        self.assertRaises(FileNotFoundError, target.open)
+        with self.assertRaises(FileNotFoundError):
+            target.open(encoding='utf-8')
 
 
 class OpenDiskTests(OpenTests, unittest.TestCase):
diff --git a/Lib/test/test_importlib/resources/test_path.py b/Lib/test/test_importlib/resources/test_path.py
index adcf75f..34a6bdd 100644
--- a/Lib/test/test_importlib/resources/test_path.py
+++ b/Lib/test/test_importlib/resources/test_path.py
@@ -14,9 +14,12 @@ class CommonTests(util.CommonTests, unittest.TestCase):
 
 class PathTests:
     def test_reading(self):
-        # Path should be readable.
-        # Test also implicitly verifies the returned object is a pathlib.Path
-        # instance.
+        """
+        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))
@@ -51,8 +54,10 @@ class PathMemoryTests(PathTests, unittest.TestCase):
 
 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.
+        """
+        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()
diff --git a/Lib/test/test_importlib/resources/test_read.py b/Lib/test/test_importlib/resources/test_read.py
index 0ca8ee9..0889826 100644
--- a/Lib/test/test_importlib/resources/test_read.py
+++ b/Lib/test/test_importlib/resources/test_read.py
@@ -12,7 +12,7 @@ class CommonBinaryTests(util.CommonTests, unittest.TestCase):
 
 class CommonTextTests(util.CommonTests, unittest.TestCase):
     def execute(self, package, path):
-        resources.files(package).joinpath(path).read_text()
+        resources.files(package).joinpath(path).read_text(encoding='utf-8')
 
 
 class ReadTests:
@@ -21,7 +21,11 @@ class ReadTests:
         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()
+        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):
@@ -33,7 +37,9 @@ class ReadTests:
         self.assertEqual(result, 'Hello, UTF-16 world!\n')
 
     def test_read_text_with_errors(self):
-        # Raises UnicodeError without the 'errors' argument.
+        """
+        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')
diff --git a/Lib/test/test_importlib/resources/test_reader.py b/Lib/test/test_importlib/resources/test_reader.py
index 4fd9e6b..8670f72 100644
--- a/Lib/test/test_importlib/resources/test_reader.py
+++ b/Lib/test/test_importlib/resources/test_reader.py
@@ -81,6 +81,17 @@ class MultiplexedPathTest(unittest.TestCase):
         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)),
diff --git a/Lib/test/test_importlib/resources/test_resource.py b/Lib/test/test_importlib/resources/test_resource.py
index f7e3abb..6f75cf5 100644
--- a/Lib/test/test_importlib/resources/test_resource.py
+++ b/Lib/test/test_importlib/resources/test_resource.py
@@ -1,3 +1,4 @@
+import contextlib
 import sys
 import unittest
 import uuid
@@ -7,7 +8,7 @@ from . import data01
 from . import zipdata01, zipdata02
 from . import util
 from importlib import resources, import_module
-from test.support import import_helper
+from test.support import import_helper, os_helper
 from test.support.os_helper import unlink
 
 
@@ -69,10 +70,12 @@ class ResourceLoaderTests(unittest.TestCase):
 
 class ResourceCornerCaseTests(unittest.TestCase):
     def test_package_has_no_reader_fallback(self):
-        # Test odd ball packages which:
+        """
+        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']
         )
@@ -138,82 +141,71 @@ class ResourceFromZipsTest02(util.ZipSetupBase, unittest.TestCase):
         )
 
 
+@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.
     """
 
-    ZIP_MODULE = zipdata01
-
     def setUp(self):
+        self.fixtures = contextlib.ExitStack()
+        self.addCleanup(self.fixtures.close)
+
         modules = import_helper.modules_setup()
         self.addCleanup(import_helper.modules_cleanup, *modules)
 
-        data_path = pathlib.Path(self.ZIP_MODULE.__file__)
-        data_dir = data_path.parent
-        self.source_zip_path = data_dir / 'ziptestdata.zip'
-        self.zip_path = pathlib.Path(f'{uuid.uuid4()}.zip').absolute()
-        self.zip_path.write_bytes(self.source_zip_path.read_bytes())
-        sys.path.append(str(self.zip_path))
-        self.data = import_module('ziptestdata')
-
-    def tearDown(self):
-        try:
-            sys.path.remove(str(self.zip_path))
-        except ValueError:
-            pass
-
-        try:
-            del sys.path_importer_cache[str(self.zip_path)]
-            del sys.modules[self.data.__name__]
-        except KeyError:
-            pass
-
-        try:
-            unlink(self.zip_path)
-        except OSError:
-            # If the test fails, this will probably fail too
-            pass
+        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):
-        c = [item.name for item in resources.files('ziptestdata').iterdir()]
-        self.zip_path.unlink()
-        del c
+        [item.name for item in resources.files('ziptestdata').iterdir()]
 
     def test_is_file_does_not_keep_open(self):
-        c = resources.files('ziptestdata').joinpath('binary.file').is_file()
-        self.zip_path.unlink()
-        del c
+        resources.files('ziptestdata').joinpath('binary.file').is_file()
 
     def test_is_file_failure_does_not_keep_open(self):
-        c = resources.files('ziptestdata').joinpath('not-present').is_file()
-        self.zip_path.unlink()
-        del c
+        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
-        c = resources.as_file(resources.files('ziptestdata') / 'binary.file')
-        self.zip_path.unlink()
-        del c
+        resources.as_file(resources.files('ziptestdata') / 'binary.file')
 
     def test_entered_path_does_not_keep_open(self):
-        # This is what certifi does on import to make its bundle
-        # available for the process duration.
-        c = resources.as_file(
-            resources.files('ziptestdata') / 'binary.file'
-        ).__enter__()
-        self.zip_path.unlink()
-        del c
+        """
+        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):
-        c = resources.files('ziptestdata').joinpath('binary.file').read_bytes()
-        self.zip_path.unlink()
-        del c
+        resources.files('ziptestdata').joinpath('binary.file').read_bytes()
 
     def test_read_text_does_not_keep_open(self):
-        c = resources.files('ziptestdata').joinpath('utf-8.file').read_text()
-        self.zip_path.unlink()
-        del c
+        resources.files('ziptestdata').joinpath('utf-8.file').read_text(
+            encoding='utf-8'
+        )
 
 
 class ResourceFromNamespaceTest01(unittest.TestCase):
diff --git a/Lib/test/test_importlib/resources/util.py b/Lib/test/test_importlib/resources/util.py
index 1e72b91..dbe6ee8 100644
--- a/Lib/test/test_importlib/resources/util.py
+++ b/Lib/test/test_importlib/resources/util.py
@@ -80,32 +80,44 @@ class CommonTests(metaclass=abc.ABCMeta):
         """
 
     def test_package_name(self):
-        # Passing in the package name should succeed.
+        """
+        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.
+        """
+        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.
+        """
+        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.
+        """
+        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.
+        """
+        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.
+        """
+        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')