pylint-macos-issue

This repository demonstrated what seems like at least one bug with pylint and macOS.

TL;DR

No virtual environment necessary. Simply use the provided Makefile.

make bug_repro

make verify_resolutions

make test

Summary of the issues

1. Inconsistency of pylint behavior when running inside a docker, but once on a mounted folder and once in a docker local folder.
2. One of the resolutions to the failure isn't supposed to really solve it.

Background

I identify the issue when my code had a slightly complex import hierarchy.

Consider module module1 that exposes both Base and Derived via its __init__.py file (see the file structure in the repo). Derived class is using Base, importing it from the module itself (and not directly).

Essentially, this might be considered a circular import, but the code works and is legal Python structure.

What we found is that pylint works just fine running a macOS, but fails inside a linux docker.

Testing the issue locally, I found that pylint has an inconsistent behavior running inside the docker.

I created a docker with the code, but also mounted the code when running the docker. Essentially, we now have 2 identical folders, one is a docker local folder, and the other is a mounted folder.

Running pylint in the local folder fails but running it in the mounted folder succeeds. Everything is identical - the files, the environment variables etc. I also checked the "report" pylint produces what asked. The stats of files and lines checked are identical.

Still, in the mounted folder it passes, but fails in the docker local folder.

Resolutions

Demonstrated in

make verify_resolutions

1. Avoid the alleged circular dependency by importing Base directly from it's contained file.
2. Add empty __init__.py to the repository root.

Where resolution #1 indeed avoids the circular dependency, resolution #2 does not. So except for the inconsistency between the local and mounted folders, there's an unexpected resolution to the issue.

What bug-repro does?

1. Shows that pylint fails on the docker local code folder.
2. Shows that pylint succeeds on the mounted folder.
3. Shows that the mounted folder and the docker local folder are identical (to prove pylint was supposed to behave exactly the same).

What verify-resolutions does?

1. Double-check pylint is still failing on the docker local folder.
2. Issue resolution 1: shows that adding an empty __init__.py in the code root will make pylint succeeds on the local folder as well.
3. Issue resolution 2: "fix" the circular dependency to statisfy pylint on the local folder as well.