pkg_resources.find_on_path() thinks the zc.recipe.egg wheel is an egg

Originally reported by: mgedmin (Bitbucket: mgedmin, GitHub: mgedmin)

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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:

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():

    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 pypa/pip#3028 for more background.

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

Original comment by mgedmin (Bitbucket: mgedmin, GitHub: mgedmin):

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Proposed fix: change the inner check to

        if path_item.lower().endswith('.egg') and os.path.isdir(os.path.join(path_item, 'EGG-INFO')):

Original comment by iElectric (Bitbucket: iElectric, GitHub: Unknown):

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I've tried that and zc.recipe.egg will still claim to be unsupported wheel.

Original comment by iElectric (Bitbucket: iElectric, GitHub: Unknown):

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Note that it occurs at multiple places:

    substituteInPlace pkg_resources/__init__.py \
      --replace "if path_item.lower().endswith('.egg'):" "if path_item.lower().endswith('.egg') and os.path.isdir(os.path.join(path_item, 'EGG-INFO')):" \
      --replace "if subitem.endswith('.egg'):" "if subitem.endswith('.egg') and os.path.isdir(os.path.join(subitem, 'EGG-INFO')):" \
      --replace "if path.lower().endswith('.egg'):" "if path.lower().endswith('.egg') and os.path.isdir(os.path.join(path, 'EGG-INFO')):" \
      --replace "lower.endswith('.egg')" "lower.endswith('.egg') and os.path.isdir(os.path.join(lower, 'EGG-INFO'))"

Original comment by jaraco (Bitbucket: jaraco, GitHub: jaraco):

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If making these changes addresses the issue, I have a patch staged and will try to push tomorrow.

Original comment by jaraco (Bitbucket: jaraco, GitHub: jaraco):

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Only detect a path as an unpacked egg if it also has an EGG-INFO directory. Fixes #462.

Original comment by jaraco (Bitbucket: jaraco, GitHub: jaraco):

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Extract function for detecting unpacked egg. Ref #462.

Original comment by jaraco (Bitbucket: jaraco, GitHub: jaraco):

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Back out 435b1b762fba. The change breaks detection of zip eggs. Reopens #462.

Original comment by jaraco (Bitbucket: jaraco, GitHub: jaraco):

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It seems that some of those tests for endswith('.egg') are also expected to match when the target is a zipped egg, and when that detection fails, it causes problems when installing zipped eggs (setuptools tests themselves fail to run).

Original comment by datakurre (Bitbucket: datakurre, GitHub: datakurre):

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Are zipped eggs just files? If so, maybe

#!python

and (os.path.isfile(path)  # is zipped egg
     or os.path.isdir(os.path.join(path, 'EGG-INFO'))

[tseaver]

The stable build of the Zope RTD docs just now failed due to this bug.

[pradyunsg]

@jaraco Would updating just a bunch of conditionals be enough to fix this?