pylint and pre-commit hook unable to import

Question

My project structure looks like this:

project/
   app/
      main.py
   venv/
   .pylintrc
   .pre-commit-config.yaml

When I am trying to edit project/app/main.py and it fails with

Unable to import 'psycopg2' (import-error)

But when I am trying to pylint this file directly, it works.

.pre-commit-config.yaml looks like this:

-   repo: https://github.com/PyCQA/pylint
    rev: pylint-2.4.2
    hooks:
    -   id: pylint

score 29 · Answer 1 · answered Apr 15 '20 at 21:03

29

not sure if this made it into pylint proper but there's a disclaimer on the bottom of pre-commit/mirrors-pylint

pre-commit runs pylint from an isolated virtualenv. Many of pylint's checks perform dynamic analysis which will fail there. You may find configuring pylint as a local hook more useful.

if you have very few dependencies, additional_dependencies might be enough to make it work, but using local hooks for things which need to (~essentially) import your code is probably your best bet

disclaimer: I'm the author of pre-commit

answered Apr 15 '20 at 21:03

anthony sottile

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1

The issue applies at least to flake8, pylint and mypy. If one takes these out of the pre-commit set of hooks they will likely ask themselves why to use pre-commit at all. I do not imply they should, just that current design limits its practical use considerably. – sorin Jun 29 '21 at 08:21
1

flake8 does not need your installed dependencies -- and it's fairly easy to get mypy working by explicitly listing your typed dependencies. I don't use pylint personally so I don't have any experience there – anthony sottile Jun 30 '21 at 11:49

score -2 · Answer 2 · answered Jun 29 '21 at 08:34

One workaround that I used in the past was to force pre-commit to install current project. Be warned that while this works is not supported by the author of pre-commit in any way, in fact being actively discouraged, mainly because it prevents pre-commit from using immutable caches.

Once the virtualenv is created it will not be updated again and pre-commit does not have any command line option to tell to not trust local cache. If you get into errors your only option is to reset the entire pre-commit disk cache, this likely means removing gigabytes of data from ~/.cache./pre-commit when you run pre-commit clean. Doing that will slowdown running pre-commit on all other projects you have... :(

Ideally the tool should have an option to invalidate only the environments from the current project and not entire cache.

- repo: https://github.com/pre-commit/mirrors-pylint
  rev: v3.0.0a3
  hooks:
  - id: pylint
    additional_dependencies:
    - .  # <-- that makes it install current project
    - flaky

this does not work, `.` will install `mirrors-pylint` and not your project — anthony sottile, Jun 30 '21 at 11:51

pylint and pre-commit hook unable to import

2 Answers2

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