6.0.0 has an undeclared dependency on importlib-metadata at python 3.6

[dimbleby]

pip-compile from pip-tools 6.0 doesn't work at python 3.6, throws an error about failing to find importlib.metadata

Environment Versions

pip-tools 6.0.0, python 3.6.8 are the important ones

Steps to replicate

[root@72c74788e4f9 /]# python3 -m venv /tmp/pip_tools

[root@72c74788e4f9 /]# source /tmp/pip_tools/bin/activate

(pip_tools) [root@72c74788e4f9 /]# python --version
Python 3.6.8

(pip_tools) [root@72c74788e4f9 /]# pip install pip-tools
Collecting pip-tools
  Downloading https://files.pythonhosted.org/packages/8d/81/15daf8485a9a508ee0fbbc3be328329a96efba8263863eeec331fd7972d9/pip_tools-6.0.0-py3-none-any.whl (43kB)
    100% |████████████████████████████████| 51kB 764kB/s
Collecting click>=7 (from pip-tools)
  Cache entry deserialization failed, entry ignored
  Cache entry deserialization failed, entry ignored
  Downloading https://files.pythonhosted.org/packages/d2/3d/fa76db83bf75c4f8d338c2fd15c8d33fdd7ad23a9b5e57eb6c5de26b430e/click-7.1.2-py2.py3-none-any.whl (82kB)
    100% |████████████████████████████████| 92kB 2.0MB/s
Collecting pip>=20.3 (from pip-tools)
  Cache entry deserialization failed, entry ignored
  Downloading https://files.pythonhosted.org/packages/fe/ef/60d7ba03b5c442309ef42e7d69959f73aacccd0d86008362a681c4698e83/pip-21.0.1-py3-none-any.whl (1.5MB)
    100% |████████████████████████████████| 1.5MB 879kB/s
Installing collected packages: click, pip, pip-tools
  Found existing installation: pip 9.0.3
    Uninstalling pip-9.0.3:
      Successfully uninstalled pip-9.0.3
Successfully installed click-7.1.2 pip-21.0.1 pip-tools-6.0.0

(pip_tools) [root@72c74788e4f9 /]# pip-compile --help

Expected result

Usage: pip-compile [OPTIONS] [SRC_FILES]...

  Compiles requirements.txt from requirements.in specs.

...

Actual result

Traceback (most recent call last):
  File "/tmp/pip_tools/lib64/python3.6/site-packages/pip/_vendor/pep517/meta.py", line 10, in <module>
    import importlib.metadata as imp_meta
ModuleNotFoundError: No module named 'importlib.metadata'

During handling of the above exception, another exception occurred:

Traceback (most recent call last):
  File "/tmp/pip_tools/bin/pip-compile", line 7, in <module>
    from piptools.scripts.compile import cli
  File "/tmp/pip_tools/lib64/python3.6/site-packages/piptools/scripts/compile.py", line 12, in <module>
    from pip._vendor.pep517 import meta
  File "/tmp/pip_tools/lib64/python3.6/site-packages/pip/_vendor/pep517/meta.py", line 12, in <module>
    import importlib_metadata as imp_meta
ModuleNotFoundError: No module named 'importlib_metadata'

[wizpig64]

I have the same issue on my 3.6 projects when they pip-compile.

But, if the import is coming from within pip, wouldn't this be pip's fault, for not depending on this properly when it vendored pep517?

edit: it looks like pep517 requires importlib_metadata for python<3.8

[dimbleby]

pip is not broken, and I expect that pip maintainers would say: if pip-tools chooses to rely on the internals of pip, then it is pip-tools problem to make that work.

(I don't know why pip-tools doesn't depend on pep517 directly, probably there's a good reason)

[dimbleby]

I see there was discussion on whether or not to use pip's private vendored copy of pep517 at #1311 (comment)

FWIW I'm on team prefer-public-APIs, and I think this issue supports that. But, maintainer's choice!

[atugushev]

Hello @dimbleby,

Thanks for the report! Huh, that was overlooked somehow. The fix is on the way.

[Cheukting]

I have the same issue, it breaks my 3.6 and 3.7 builds. The patch 6.0.1 is not on PyPI yet, guess I will have to roll back to the previous version for now?

[vphilippon]

FYI I'm attempting to get the 6.0.1 fix out right now, but the GH Actions seems to have a rather long queue time and having issues starting the job.
I'll keep you posted as soon as I get it through.

[Cheukting]

Thanks. My GH action is not deploying my library as well.. guess GH action is down at the moment? Don't worry, I am back to 5.5.0 at the moment but is happy to use the new version when it's back up again.

[vphilippon]

There we go, pip-tools 6.0.1 is now released and available on PyPI! 🎉

[Cheukting]

Amazing! Thanks @vphilippon