Attempt to install editable packge defined in constraints should error

[nakato]

Currently if the local package you are trying to install is listed in
the constraint file it will silently fail to install the local package
while installing its dependencies.

This process was caused by the has_requirement returning true when a
constraint with that name was defined, resulting in the local package
not being processed.

Closes #2928

[rbtcollins]

I think this is still buggy. The error you look for says to me that the code is trying to install the constrained version. But the users requested actions are actually inconsistent: we can't both install the constrained version and install the editable version.

So I think we specifically want an error like the error that occurs if you put the following in a requirements file:

foo==1
foo==2

[rbtcollins]

(test)robertc@trusty-64:~/work/pip$ git checkout FETCH_HEAD
Previous HEAD position was 40242fe... Merge pull request #2934 from jamezpolley/user_implies_null_prefix
HEAD is now at e2c154a... Attempt to install editable packge defined in constraints should error
(test)robertc@trusty-64:~/work/pip$ pip install -e .
Obtaining file:///home/robertc/work/pip
Installing collected packages: pip
  Running setup.py develop for pip
Successfully installed pip-7.1.0.dev0
(test)robertc@trusty-64:~/work/pip$ pip install -c constraints.txt -e . 
Obtaining file:///home/robertc/work/pip
Collecting pip==7.0.3 (from -c constraints.txt (line 1))
/home/robertc/work/pip/pip/_vendor/requests/packages/urllib3/util/ssl_.py:90: InsecurePlatformWarning: A true SSLContext object is not available. This prevents urllib3 from configuring SSL appropriately and may cause certain SSL connections to fail. For more information, see https://urllib3.readthedocs.org/en/latest/security.html#insecureplatformwarning.
  InsecurePlatformWarning
  Using cached pip-7.0.3-py2.py3-none-any.whl
Installing collected packages: pip
  Found existing installation: pip 7.1.0.dev0
    Uninstalling pip-7.1.0.dev0:
      Successfully uninstalled pip-7.1.0.dev0
Successfully installed pip-7.1.0.dev0
(test)robertc@trusty-64:~/work/pip$ pip list | grep pip
pip (7.1.0.dev0)

So its -very- confused.

[rbtcollins]

rather than making a new one, use singlemodule.

Its in an index in data/packages/ versions 0.0.0 and 0.0.1 and it's source is in data/src/singlemodule. So you can constrain to version 0.0.0 and use -f data/packages --no-index -e src/singlemodule.

[nakato]

That's quite a bit cleaner than adding a new package. Done.

[rbtcollins]

Hey thats looking super close.

I wonder if its possible to make it support this test as well?

def test_constrained_to_url_install_same_url(script, data):
    to_install = data.src.join("singlemodule")
    script.scratch_path.join("constraints.txt").write(
        "file://%s#egg=singlemodule" % to_install
    )
    result = script.pip(
        'install', '--no-index', '-f', data.find_links, '-c',
        script.scratch_path / 'constraints.txt', to_install)
    assert 'Running setup.py install for singlemodule' in result.stdout

[rbtcollins]

\o/ this looks solid to me. @dstufft ?

[nakato]

I'm expecting this to fail.

[nakato]

Latest change is a rebase to top of develop. Just to get the updated dev-requirements.txt

[nakato]

After a discussion with lifeless this morning, I found out that putting the controversial patch in a separate branch and create a pull request for it and things will just work. So I've split that off to a new PR. As far as I'm concerned these two are all good to go.