Breaking change as a result of egg fragment mismatch changes

[andybak]

Related to: #3153

Last year I discovered that if my requirements.txt installs were from git branches:

-e git+https://github.com/Foo/bar.git@feature/baz@feature1#egg=bar

then I changed the branch:

-e git+https://github.com/Foo/bar.git@feature/baz@feature2#egg=bar

then a pip install -U failed to work correctly (apologies - I can't remember exactly what failed)

After a lot of hair pulling I figured out the fix (for me at least) was to ensure I always updated the egg name:

-e git+https://github.com/Foo/bar.git@feature/baz@feature1#egg=bar-feature1

and

-e git+https://github.com/Foo/bar.git@feature/baz@feature2#egg=bar-feature2

After 3153 and related PRs were merged I noticed the warnings about "egg_info for package X produced metadata for project name Y Fix your #eggfragments." but as it was only a warning I didn't delve into it at the time.

I've just discovered that packages with this warning don't uninstall - I have to manually delete remnants from src and site-packages. This is going to be a pain as it requires manually going through deployments to about 20 separate websites.

Now - my workaround wasn't documented and was probably incorrect - but I'm creating an issue just in case I wasn't alone in this and in case it is useful to the pip developers. If it's a case of "you shouldn't have done something so dumb" then feel free to close the ticket.

[xavfernandez]

This seems to be resolved:

(tmp-fd85baa2204aedc) $ pip install -e git+https://github.com/PyCQA/mccabe.git@bug/39#egg=mccabe --upgrade
Obtaining mccabe from git+https://github.com/PyCQA/mccabe.git@bug/39#egg=mccabe
  Updating ./src/mccabe clone (to bug/39)
Installing collected packages: mccabe
  Found existing installation: mccabe 0.6.1
    Uninstalling mccabe-0.6.1:
      Successfully uninstalled mccabe-0.6.1
  Running setup.py develop for mccabe
Successfully installed mccabe
(tmp-fd85baa2204aedc) $ pip install -e git+https://github.com/PyCQA/mccabe.git@master#egg=mccabe --upgrade
Obtaining mccabe from git+https://github.com/PyCQA/mccabe.git@master#egg=mccabe
  Updating ./src/mccabe clone (to master)
Installing collected packages: mccabe
  Found existing installation: mccabe 0.5.0
    Uninstalling mccabe-0.5.0:
      Successfully uninstalled mccabe-0.5.0
  Running setup.py develop for mccabe
Successfully installed mccabe