Support .egg installations

Signed-off-by: Anthony Sottile <[email protected]>

MANIFEST.in

@@ -1,5 +1,5 @@
 include *.py MANIFEST.in LICENSE README.rst
-global-include *.txt *.rst *.ini *.cfg *.toml *.whl
+global-include *.txt *.rst *.ini *.cfg *.toml *.whl *.egg
 exclude .gitignore
 prune build
 prune .tox

README.rst

@@ -26,36 +26,6 @@ tools (or other conforming packages). It does not support:
 
 - Packages in the stdlib.
 - Packages installed without metadata.
-- Packages installed as eggs.
-
-Eggs
-----
-
-Not only does ``importlib_metadata`` not support loading metadata
-from eggs, it will crash when it attempts to load metadata for
-any package that's an egg.
-
-``easy_install`` creates eggs when installing packages, which is why
-you should use ``pip`` to install packages. ``pip`` never installs
-eggs. There are some cases, however, where a project's usage
-may not be able to avoid ``easy_install``. In particular, if a project
-uses ``setup.py test``, any ``install_requires`` of that project that
-aren't already installed will be installed using ``easy_install``.
-Additionally, any project defining ``setup_requires`` may get those
-dependencies installed as eggs if those dependencies aren't met before
-setup.py is invoked (for any command).
-
-Because ``importlib_metadata`` doesn't support loading metadata from
-eggs and because ``importlib_metadata`` calls itself to get its own version,
-simply importing ``importlib_metadata`` will fail if it is installed as an
-egg. Any package that incorporates ``importlib_metadata`` (directly
-or indirectly) should be prepared to guide its users to tools that avoid
-installing eggs (such as `pip <https://pypi.org/project/pip>`_ and
-`tox <https://pypi.org/project/tox>`_).
-
-More detail and discussion can be found at
-`issue 19 <https://gitlab.com/python-devs/importlib_metadata/issues/19>`_.
-
 
 Project details
 ===============

importlib_metadata/_hooks.py

@@ -57,7 +57,7 @@ class MetadataPathFinder(NullFinder):
     This finder supplies only a find_distributions() method for versions
     of Python that do not have a PathFinder find_distributions().
     """
-    search_template = r'{pattern}(-.*)?\.(dist|egg)-info'
+    search_template = r'(?:{pattern}(-.*)?\.(dist|egg)-info|EGG-INFO)'
 
     def find_distributions(self, name=None, path=None):
         """Return an iterable of all Distribution instances capable of

importlib_metadata/tests/test_zip.py

@@ -14,13 +14,9 @@
     from contextlib2 import ExitStack
 
 
-class BespokeLoader:
-    archive = 'bespoke'
-
-
 class TestZip(unittest.TestCase):
     def setUp(self):
-        # Find the path to the example.*.whl so we can add it to the front of
+        # Find the path to the example-*.whl so we can add it to the front of
         # sys.path, where we'll then try to find the metadata thereof.
         self.resources = ExitStack()
         self.addCleanup(self.resources.close)
@@ -48,3 +44,21 @@ def test_files(self):
         for file in files('example'):
             path = str(file.dist.locate_file(file))
             assert '.whl/' in path, path
+
+
+class TestEgg(TestZip):
+    def setUp(self):
+        # Find the path to the example-*.egg so we can add it to the front of
+        # sys.path, where we'll then try to find the metadata thereof.
+        self.resources = ExitStack()
+        self.addCleanup(self.resources.close)
+        egg = self.resources.enter_context(
+            path('importlib_metadata.tests.data',
+                 'example-21.12-py3.6.egg'))
+        sys.path.insert(0, str(egg))
+        self.resources.callback(sys.path.pop, 0)
+
+    def test_files(self):
+        for file in files('example'):
+            path = str(file.dist.locate_file(file))
+            assert '.egg/' in path, path

setup.cfg

@@ -28,8 +28,9 @@ packages = find:
 importlib_metadata =
     docs/*
     docs/_static/*
-importlib_metadata.tests.data03 =
-    namespace/*
+importlib_metadata.tests.data =
+    *.egg
+    *.whl
 
 [mypy]
 ignore_missing_imports = True