gh-93259: Validate arg to ``Distribution.from_name``. (GH-94270)

Syncs with importlib_metadata 4.12.0.

4 files changed, 102 insertions, 59 deletions

diff --git a/Lib/importlib/metadata/__init__.py b/Lib/importlib/metadata/__init__.py
index 9ceae8a..b01de14 100644
--- a/Lib/importlib/metadata/__init__.py
+++ b/Lib/importlib/metadata/__init__.py
@@ -543,7 +543,7 @@ class Distribution:
         """
 
     @classmethod
-    def from_name(cls, name):
+    def from_name(cls, name: str):
         """Return the Distribution for the given package name.
 
         :param name: The name of the distribution package to search for.
@@ -551,13 +551,13 @@ class Distribution:
             package, if found.
         :raises PackageNotFoundError: When the named package's distribution
             metadata cannot be found.
+        :raises ValueError: When an invalid value is supplied for name.
         """
-        for resolver in cls._discover_resolvers():
-            dists = resolver(DistributionFinder.Context(name=name))
-            dist = next(iter(dists), None)
-            if dist is not None:
-                return dist
-        else:
+        if not name:
+            raise ValueError("A distribution name is required.")
+        try:
+            return next(cls.discover(name=name))
+        except StopIteration:
             raise PackageNotFoundError(name)
 
     @classmethod
@@ -945,13 +945,26 @@ class PathDistribution(Distribution):
         normalized name from the file system path.
         """
         stem = os.path.basename(str(self._path))
-        return self._name_from_stem(stem) or super()._normalized_name
+        return (
+            pass_none(Prepared.normalize)(self._name_from_stem(stem))
+            or super()._normalized_name
+        )
 
-    def _name_from_stem(self, stem):
-        name, ext = os.path.splitext(stem)
+    @staticmethod
+    def _name_from_stem(stem):
+        """
+        >>> PathDistribution._name_from_stem('foo-3.0.egg-info')
+        'foo'
+        >>> PathDistribution._name_from_stem('CherryPy-3.0.dist-info')
+        'CherryPy'
+        >>> PathDistribution._name_from_stem('face.egg-info')
+        'face'
+        >>> PathDistribution._name_from_stem('foo.bar')
+        """
+        filename, ext = os.path.splitext(stem)
         if ext not in ('.dist-info', '.egg-info'):
             return
-        name, sep, rest = stem.partition('-')
+        name, sep, rest = filename.partition('-')
         return name
 
 
@@ -991,6 +1004,15 @@ def version(distribution_name):
     return distribution(distribution_name).version
 
 
+_unique = functools.partial(
+    unique_everseen,
+    key=operator.attrgetter('_normalized_name'),
+)
+"""
+Wrapper for ``distributions`` to return unique distributions by name.
+"""
+
+
 def entry_points(**params) -> Union[EntryPoints, SelectableGroups]:
     """Return EntryPoint objects for all installed packages.
 
@@ -1008,10 +1030,8 @@ def entry_points(**params) -> Union[EntryPoints, SelectableGroups]:
 
     :return: EntryPoints or SelectableGroups for all installed packages.
     """
-    norm_name = operator.attrgetter('_normalized_name')
-    unique = functools.partial(unique_everseen, key=norm_name)
     eps = itertools.chain.from_iterable(
-        dist.entry_points for dist in unique(distributions())
+        dist.entry_points for dist in _unique(distributions())
     )
     return SelectableGroups.load(eps).select(**params)
 
diff --git a/Lib/test/test_importlib/fixtures.py b/Lib/test/test_importlib/fixtures.py
index 803d373..e7be77b 100644
--- a/Lib/test/test_importlib/fixtures.py
+++ b/Lib/test/test_importlib/fixtures.py
@@ -5,6 +5,7 @@ import shutil
 import pathlib
 import tempfile
 import textwrap
+import functools
 import contextlib
 
 from test.support.os_helper import FS_NONASCII
@@ -296,3 +297,18 @@ class ZipFixtures:
         # Add self.zip_name to the front of sys.path.
         self.resources = contextlib.ExitStack()
         self.addCleanup(self.resources.close)
+
+
+def parameterize(*args_set):
+    """Run test method with a series of parameters."""
+
+    def wrapper(func):
+        @functools.wraps(func)
+        def _inner(self):
+            for args in args_set:
+                with self.subTest(**args):
+                    func(self, **args)
+
+        return _inner
+
+    return wrapper
diff --git a/Lib/test/test_importlib/test_main.py b/Lib/test/test_importlib/test_main.py
index c80a0e4..d9d067c 100644
--- a/Lib/test/test_importlib/test_main.py
+++ b/Lib/test/test_importlib/test_main.py
@@ -1,7 +1,6 @@
 import re
 import json
 import pickle
-import textwrap
 import unittest
 import warnings
 import importlib.metadata
@@ -16,6 +15,7 @@ from importlib.metadata import (
     Distribution,
     EntryPoint,
     PackageNotFoundError,
+    _unique,
     distributions,
     entry_points,
     metadata,
@@ -51,6 +51,14 @@ class BasicTests(fixtures.DistInfoPkg, unittest.TestCase):
     def test_new_style_classes(self):
         self.assertIsInstance(Distribution, type)
 
+    @fixtures.parameterize(
+        dict(name=None),
+        dict(name=''),
+    )
+    def test_invalid_inputs_to_from_name(self, name):
+        with self.assertRaises(Exception):
+            Distribution.from_name(name)
+
 
 class ImportTests(fixtures.DistInfoPkg, unittest.TestCase):
     def test_import_nonexistent_module(self):
@@ -78,48 +86,50 @@ class ImportTests(fixtures.DistInfoPkg, unittest.TestCase):
 
 class NameNormalizationTests(fixtures.OnSysPath, fixtures.SiteDir, unittest.TestCase):
     @staticmethod
-    def pkg_with_dashes(site_dir):
+    def make_pkg(name):
         """
-        Create minimal metadata for a package with dashes
-        in the name (and thus underscores in the filename).
+        Create minimal metadata for a dist-info package with
+        the indicated name on the file system.
         """
-        metadata_dir = site_dir / 'my_pkg.dist-info'
-        metadata_dir.mkdir()
-        metadata = metadata_dir / 'METADATA'
-        with metadata.open('w', encoding='utf-8') as strm:
-            strm.write('Version: 1.0\n')
-        return 'my-pkg'
+        return {
+            f'{name}.dist-info': {
+                'METADATA': 'VERSION: 1.0\n',
+            },
+        }
 
     def test_dashes_in_dist_name_found_as_underscores(self):
         """
         For a package with a dash in the name, the dist-info metadata
         uses underscores in the name. Ensure the metadata loads.
         """
-        pkg_name = self.pkg_with_dashes(self.site_dir)
-        assert version(pkg_name) == '1.0'
-
-    @staticmethod
-    def pkg_with_mixed_case(site_dir):
-        """
-        Create minimal metadata for a package with mixed case
-        in the name.
-        """
-        metadata_dir = site_dir / 'CherryPy.dist-info'
-        metadata_dir.mkdir()
-        metadata = metadata_dir / 'METADATA'
-        with metadata.open('w', encoding='utf-8') as strm:
-            strm.write('Version: 1.0\n')
-        return 'CherryPy'
+        fixtures.build_files(self.make_pkg('my_pkg'), self.site_dir)
+        assert version('my-pkg') == '1.0'
 
     def test_dist_name_found_as_any_case(self):
         """
         Ensure the metadata loads when queried with any case.
         """
-        pkg_name = self.pkg_with_mixed_case(self.site_dir)
+        pkg_name = 'CherryPy'
+        fixtures.build_files(self.make_pkg(pkg_name), self.site_dir)
         assert version(pkg_name) == '1.0'
         assert version(pkg_name.lower()) == '1.0'
         assert version(pkg_name.upper()) == '1.0'
 
+    def test_unique_distributions(self):
+        """
+        Two distributions varying only by non-normalized name on
+        the file system should resolve as the same.
+        """
+        fixtures.build_files(self.make_pkg('abc'), self.site_dir)
+        before = list(_unique(distributions()))
+
+        alt_site_dir = self.fixtures.enter_context(fixtures.tempdir())
+        self.fixtures.enter_context(self.add_sys_path(alt_site_dir))
+        fixtures.build_files(self.make_pkg('ABC'), alt_site_dir)
+        after = list(_unique(distributions()))
+
+        assert len(after) == len(before)
+
 
 class NonASCIITests(fixtures.OnSysPath, fixtures.SiteDir, unittest.TestCase):
     @staticmethod
@@ -128,11 +138,12 @@ class NonASCIITests(fixtures.OnSysPath, fixtures.SiteDir, unittest.TestCase):
         Create minimal metadata for a package with non-ASCII in
         the description.
         """
-        metadata_dir = site_dir / 'portend.dist-info'
-        metadata_dir.mkdir()
-        metadata = metadata_dir / 'METADATA'
-        with metadata.open('w', encoding='utf-8') as fp:
-            fp.write('Description: pôrˈtend')
+        contents = {
+            'portend.dist-info': {
+                'METADATA': 'Description: pôrˈtend',
+            },
+        }
+        fixtures.build_files(contents, site_dir)
         return 'portend'
 
     @staticmethod
@@ -141,19 +152,15 @@ class NonASCIITests(fixtures.OnSysPath, fixtures.SiteDir, unittest.TestCase):
         Create minimal metadata for an egg-info package with
         non-ASCII in the description.
         """
-        metadata_dir = site_dir / 'portend.dist-info'
-        metadata_dir.mkdir()
-        metadata = metadata_dir / 'METADATA'
-        with metadata.open('w', encoding='utf-8') as fp:
-            fp.write(
-                textwrap.dedent(
-                    """
+        contents = {
+            'portend.dist-info': {
+                'METADATA': """
                 Name: portend
 
-                pôrˈtend
-                """
-                ).strip()
-            )
+                pôrˈtend""",
+            },
+        }
+        fixtures.build_files(contents, site_dir)
         return 'portend'
 
     def test_metadata_loads(self):
diff --git a/Lib/test/test_importlib/test_metadata_api.py b/Lib/test/test_importlib/test_metadata_api.py
index c86bb4d..69c78e9 100644
--- a/Lib/test/test_importlib/test_metadata_api.py
+++ b/Lib/test/test_importlib/test_metadata_api.py
@@ -89,15 +89,15 @@ class APITests(
             self.assertIn(ep.dist.name, ('distinfo-pkg', 'egginfo-pkg'))
             self.assertEqual(ep.dist.version, "1.0.0")
 
-    def test_entry_points_unique_packages(self):
+    def test_entry_points_unique_packages_normalized(self):
         """
         Entry points should only be exposed for the first package
-        on sys.path with a given name.
+        on sys.path with a given name (even when normalized).
         """
         alt_site_dir = self.fixtures.enter_context(fixtures.tempdir())
         self.fixtures.enter_context(self.add_sys_path(alt_site_dir))
         alt_pkg = {
-            "distinfo_pkg-1.1.0.dist-info": {
+            "DistInfo_pkg-1.1.0.dist-info": {
                 "METADATA": """
                 Name: distinfo-pkg
                 Version: 1.1.0