Repository: pypa/setuptools (python)

Issue:
pkg_resources.find_on_path() thinks the zc.recipe.egg wheel is an egg
Originally reported by: **mgedmin (Bitbucket: [mgedmin](http://bitbucket.org/mgedmin), GitHub: [mgedmin](http://github.com/mgedmin))**

---

Steps to reproduce: try to `pip install zc.recipe.egg`.  You'll get an error:

```
zc.recipe.egg is in an unsupported or invalid wheel
```

If you hack pip's sources to expose the real traceback, you'll see [this](https://github.com/pypa/pip/issues/3028#issuecomment-148614984):

```
Traceback (most recent call last):                                                                                                                                                                                                           
  File "/home/qwcode/p/pypa/pip/pip/basecommand.py", line 200, in main                                                                                                                                                                       
    status = self.run(options, args)                                                                                                                                                                                                         
  File "/home/qwcode/p/pypa/pip/pip/commands/install.py", line 302, in run                                                                                                                                                                   
    root=options.root_path,                                                                                                                                                                                                                  
  File "/home/qwcode/p/pypa/pip/pip/req/req_set.py", line 657, in install                                                                                                                                                                    
    **kwargs
  File "/home/qwcode/p/pypa/pip/pip/req/req_install.py", line 805, in install
    version = pip.wheel.wheel_version(self.source_dir)
  File "/home/qwcode/p/pypa/pip/pip/wheel.py", line 559, in wheel_version
    wheel_data = dist.get_metadata('WHEEL')
  File "/home/qwcode/p/pypa/pip/pip/_vendor/pkg_resources/__init__.py", line 1611, in get_metadata
    return self._get(self._fn(self.egg_info, name))
  File "/home/qwcode/p/pypa/pip/pip/_vendor/pkg_resources/__init__.py", line 1722, in _get
    with open(path, 'rb') as stream:
IOError: [Errno 2] No such file or directory: '/tmp/pip-build-ucnzjI/zc.recipe.egg/EGG-INFO/WHEEL'
```

AFAIU the problem is the following check in pkg_resources.find_on_path():

``` python
    if os.path.isdir(path_item) and os.access(path_item, os.R_OK):
        if path_item.lower().endswith('.egg'):
            # unpacked egg
```

This is wrong: the unpacked zc.recipe.egg _wheel_ has a top-level directory called `zc.recipe.egg`.

See https://github.com/pypa/pip/issues/3028 for more background.

---
- Bitbucket: https://bitbucket.org/pypa/setuptools/issue/462


Pull request description:
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

Should also close pypa/pip#3028

Patch:
diff --git a/.gitignore b/.gitignore
index b23ade08c..2e2f71b8f 100644
--- a/.gitignore
+++ b/.gitignore
@@ -7,6 +7,7 @@ lib
 distribute.egg-info
 setuptools.egg-info
 .coverage
+.eggs
 .tox
 *.egg
 *.py[cod]
diff --git a/CHANGES.rst b/CHANGES.rst
index 75f39d482..7baca6565 100644
--- a/CHANGES.rst
+++ b/CHANGES.rst
@@ -1,3 +1,9 @@
+v36.2.6
+-------
+
+* #462: Don't assume a directory is an egg by the ``.egg``
+  extension alone.
+
 v36.2.5
 -------
 
diff --git a/pkg_resources/__init__.py b/pkg_resources/__init__.py
index f6666968b..f13a69b30 100644
--- a/pkg_resources/__init__.py
+++ b/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'))
     )
 
 
diff --git a/setup.py b/setup.py
index 9571cfa97..7b29c53ee 100755
--- a/setup.py
+++ b/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",


Test patch:
diff --git a/pkg_resources/tests/test_find_distributions.py b/pkg_resources/tests/test_find_distributions.py
new file mode 100644
index 000000000..97999b335
--- /dev/null
+++ b/pkg_resources/tests/test_find_distributions.py
@@ -0,0 +1,65 @@
+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)
diff --git a/tests/requirements.txt b/tests/requirements.txt
index c9413b86d..4761505fc 100644
--- a/tests/requirements.txt
+++ b/tests/requirements.txt
@@ -1,5 +1,6 @@
 importlib; python_version<"2.7"
 mock
 pytest-flake8; python_version>="2.7"
+virtualenv>=13.0.0
 pytest-virtualenv>=1.2.7
 pytest>=3.0.2