How to pre-install pre commit into hooks into docker - pre-commit.com

Question

As I understand the documentation, whenever I add these lines to the config:
repos:
- repo: https://github.com/pre-commit/pre-commit-hooks
rev: v2.1.0
hooks:
- id: trailing-whitespace
it makes pre-commit to download the hooks code from this repo and execute it. Is it possible to pre-install all the hooks somehow into a Docker image. So when I call pre-commit run no network is used?
I found this section of the documentation describing how pre-commit caches all the repositories. They are stored in ~/.cache/pre-commit and this could be configured by updating PRE_COMMIT_HOME env variable.
However, the caching only works when I do pre-commit run. But I want to pre-install everything w/o running the checks. Is it possible?

Answer 1

you're looking for the pre-commit install-hooks command
at the least you need something like this to cache the pre-commit environments:
COPY .pre-commit-config.yaml .
RUN git init . && pre-commit install-hooks
disclaimer: I created pre-commit

Answer 2

Snippet provided by #anthony-sottile works like charm. It helps utilize docker cache. Here is a working variation for it from django world.
ARG PYTHON_VERSION=3.9-buster
# define an alias for the specfic python version used in this file.
FROM python:${PYTHON_VERSION} as python
# Python build stage
FROM python as python-build-stage
ARG BUILD_ENVIRONMENT=test
# Install apt packages
RUN apt-get update && apt-get install --no-install-recommends -y \
# dependencies for building Python packages
build-essential \
# psycopg2 dependencies
libpq-dev
# Requirements are installed here to ensure they will be cached.
COPY ./requirements .
# Create Python Dependency and Sub-Dependency Wheels.
RUN pip wheel --wheel-dir /usr/src/app/wheels \
-r ${BUILD_ENVIRONMENT}.txt
# Python 'run' stage
FROM python as python-run-stage
ARG BUILD_ENVIRONMENT=test
ARG APP_HOME=/app
ENV PYTHONUNBUFFERED 1
ENV PYTHONDONTWRITEBYTECODE 1
ENV BUILD_ENV ${BUILD_ENVIRONMENT}
WORKDIR ${APP_HOME}
# Install required system dependencies
RUN apt-get update && apt-get install --no-install-recommends -y \
# psycopg2 dependencies
libpq-dev \
# Translations dependencies
gettext \
# cleaning up unused files
&& apt-get purge -y --auto-remove -o APT::AutoRemove::RecommendsImportant=false \
&& rm -rf /var/lib/apt/lists/*
# All absolute dir copies ignore workdir instruction. All relative dir copies are wrt to the workdir instruction
# copy python dependency wheels from python-build-stage
COPY --from=python-build-stage /usr/src/app/wheels /wheels/
# use wheels to install python dependencies
RUN pip install --no-cache-dir --no-index --find-links=/wheels/ /wheels/* \
&& rm -rf /wheels/
COPY ./compose/test/django/entrypoint /entrypoint
RUN chmod +x /entrypoint
COPY .pre-commit-config.yaml .
RUN git init . && pre-commit install-hooks
# copy application code to WORKDIR
COPY . ${APP_HOME}
ENTRYPOINT ["/entrypoint"]
then you can fire pre-commit checks in similar fashion:
docker-compose -p project_name -f test.yml run --rm django pre-commit run --all-files