Better detect unpacked eggs

Do not assume a directory named in `.egg` is an egg, unless it has an
actual egg metadata directory.

Closes #462

CHANGES.rst

+v36.2.6
+-------
+
+* #462: Don't assume a directory is an egg by the ``.egg``
+  extension alone.
+
 v36.2.5
 -------
 

pkg_resources/__init__.py

@@ -1553,7 +1553,7 @@ class EggProvider(NullProvider):
         path = self.module_path
         old = None
         while path != old:
-            if _is_unpacked_egg(path):
+            if _is_egg_path(path):
                 self.egg_name = os.path.basename(path)
                 self.egg_info = os.path.join(path, 'EGG-INFO')
                 self.egg_root = path
@@ -1956,7 +1956,7 @@ def find_eggs_in_zip(importer, path_item, only=False):
         # don't yield nested distros
         return
     for subitem in metadata.resource_listdir('/'):
-        if _is_unpacked_egg(subitem):
+        if _is_egg_path(subitem):
             subpath = os.path.join(path_item, subitem)
             for dist in find_eggs_in_zip(zipimport.zipimporter(subpath), subpath):
                 yield dist
@@ -2033,7 +2033,7 @@ def find_on_path(importer, path_item, only=False):
                     yield Distribution.from_location(
                         path_item, entry, metadata, precedence=DEVELOP_DIST
                     )
-                elif not only and _is_unpacked_egg(entry):
+                elif not only and _is_egg_path(entry):
                     dists = find_distributions(os.path.join(path_item, entry))
                     for dist in dists:
                         yield dist
@@ -2221,12 +2221,22 @@ def _normalize_cached(filename, _cache={}):
         return result
 
 
+def _is_egg_path(path):
+    """
+    Determine if given path appears to be an egg.
+    """
+    return (
+        path.lower().endswith('.egg')
+    )
+
+
 def _is_unpacked_egg(path):
     """
     Determine if given path appears to be an unpacked egg.
     """
     return (
-        path.lower().endswith('.egg')
+        _is_egg_path(path) and
+        os.path.isfile(os.path.join(path, 'EGG-INFO', 'PKG-INFO'))
     )
 
 

pkg_resources/tests/test_find_distributions.py

+import subprocess
+import sys
+
+import pytest
+import pkg_resources
+
+SETUP_TEMPLATE = """
+import setuptools
+setuptools.setup(
+    name="my-test-package",
+    version="1.0",
+    zip_safe=True,
+)
+""".lstrip()
+
+class TestFindDistributions:
+
+    @pytest.fixture
+    def target_dir(self, tmpdir):
+        target_dir = tmpdir.mkdir('target')
+        # place a .egg named directory in the target that is not an egg:
+        target_dir.mkdir('not.an.egg')
+        return str(target_dir)
+
+    @pytest.fixture
+    def project_dir(self, tmpdir):
+        project_dir = tmpdir.mkdir('my-test-package')
+        (project_dir / "setup.py").write(SETUP_TEMPLATE)
+        return str(project_dir)
+
+    def test_non_egg_dir_named_egg(self, target_dir):
+        dists = pkg_resources.find_distributions(target_dir)
+        assert not list(dists)
+
+    def test_standalone_egg_directory(self, project_dir, target_dir):
+        # install this distro as an unpacked egg:
+        args = [
+            sys.executable,
+            '-c', 'from setuptools.command.easy_install import main; main()',
+            '-mNx',
+            '-d', target_dir,
+            '--always-unzip',
+            project_dir,
+        ]
+        subprocess.check_call(args)
+        dists = pkg_resources.find_distributions(target_dir)
+        assert [dist.project_name for dist in dists] == ['my-test-package']
+        dists = pkg_resources.find_distributions(target_dir, only=True)
+        assert not list(dists)
+
+    def test_zipped_egg(self, project_dir, target_dir):
+        # install this distro as an unpacked egg:
+        args = [
+            sys.executable,
+            '-c', 'from setuptools.command.easy_install import main; main()',
+            '-mNx',
+            '-d', target_dir,
+            '--zip-ok',
+            project_dir,
+        ]
+        subprocess.check_call(args)
+        dists = pkg_resources.find_distributions(target_dir)
+        assert [dist.project_name for dist in dists] == ['my-test-package']
+        dists = pkg_resources.find_distributions(target_dir, only=True)
+        assert not list(dists)

setup.py

@@ -89,7 +89,7 @@ def pypi_link(pkg_filename):
 
 setup_params = dict(
     name="setuptools",
-    version="36.2.5",
+    version="36.2.6",
     description="Easily download, build, install, upgrade, and uninstall "
         "Python packages",
     author="Python Packaging Authority",