pre-commit-docker-flake8

What is this?

This is a proof-of-concept of providing a pre-commit hook for flake8 via docker. It is suggested to instead use flake8 as provided by pre-commit-hooks as you'll have slightly better performance and more control over the python executable.

How does this work?

pre-commit by convention mounts the user's code at /src inside the container. The executable is fed relative path filename arguments. The hook may make changes to the files as the source is mounted read-write and the executables are run as the user.

A few key lines in the Dockerfile make this work:

RUN virtualenv /venv -ppython3 && /venv/bin/pip install flake8
ENV PATH=/venv/bin:$PATH

This creates a virtual environment inside the docker image and puts the virtualenv on the PATH so executables (such as flake8) can be run.

Lastly, the metadata in hooks.yaml hooks this up:

    entry: flake8
    language: docker

Here flake8 is the executable inside the container and we tell pre-commit that the language is docker.

How would I use this repository with pre-commit?

Well, you probably wouldn't (and the hook has been labeled as such) but if you really wanted to you could add this to your .pre-commit-config.yaml:

-   repo: https://github.com/pre-commit/pre-commit-docker-flake8
    rev: ''  # Fill this in with a current revision
    hooks:
    -   id: flake8-docker-not-for-production

You'll also need to use at least version 0.10.0 of pre-commit.