Set up pre-commit

This step is entirely optional but is recommended.

Pre-commit

Pre-commit is a tool that runs git hooks on your code before you commit it. It's a great way to ensure your code is formatted correctly and passes some basic checks before you commit it.

It will run black, isort and flake8 on my code and check for missing migrations and also that requirements.txt is up to date before I commit it.

Install pre-commit

Add pre-commit to the development dependencies in Pipfile:

pipenv install --dev pre-commit

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If you already have pre-commit installed globally, you can skip this step.

Configure pre-commit

Create a .pre-commit-config.yaml file in the root of the project and add the following content:

repos:
  # These hooks make sure that the code is formatted correctly
  - repo: https://github.com/pycqa/isort
    rev: 5.12.0
    hooks:
      - id: isort
  - repo: https://github.com/psf/black
    rev: 23.7.0
    hooks:
      - id: black
  - repo: https://github.com/pycqa/flake8
    rev: 6.1.0
    hooks:
      - id: flake8

  # These hooks make sure that the requirements.txt file is up to date
  # with the latest changes to pipenv as well as making sure migrations
  # are up to date.
  - repo: local
    hooks:
      - id: check-dependencies
        name: Check dependencies
        entry: ./checks/dependencies.sh
        language: system
        types: [python]
        pass_filenames: false
        always_run: true
        stages: [pre-commit]
      - id: check-migrations
        name: Check migrations
        entry: ./checks/migrations.sh
        language: system
        types: [python]
        pass_filenames: false
        always_run: true
        stages: [commit]
      - id: check-static
        name: Check static files
        entry: ./checks/static.sh
        language: system
        types: [css, javascript]
        pass_filenames: false
        always_run: true
        stages: [pre-commit]

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Add the git hook entry points

Create a checks directory in the root of the project and add the following files:

mkdir checks
touch checks/dependencies.sh
touch checks/migrations.sh
touch checks/static.sh
chmod +x checks/*.sh

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Update the content of each file as follows:

File checks/dependencies.sh:

#!/bin/bash

# Get the contents of requirements.txt
requirements=$(cat requirements.txt)

# Get the output from pipenv requirements
pipenv_requirements=$(pipenv requirements)

# Compare the two outputs
if [ "$requirements" == "$pipenv_requirements" ]; then
  echo "Requirements are correct"
else
  echo "Requirements are different, please run pipenv requirements > requirements.txt and stage the changes"
  exit 1
fi

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File checks/migrations.sh:

#!/bin/bash

# Check if MySQL is already running
# so we can stop it after the checks if it was started here.
if docker-compose top | grep mysqld 2> /dev/null; then
    echo "MySQL is running."
    MYSQL_RUNNING=true
else
    echo "MySQL is not running."
    MYSQL_RUNNING=false
fi

if [ "$MYSQL_RUNNING" = false ]; then
    docker-compose up -d db
    echo "MySQL has been started."
fi

if pipenv run python manage.py makemigrations --check --dry-run; then
    # There are no changes to migrations
    if [ "$MYSQL_RUNNING" = false ]; then
        docker-compose stop db
        echo "MySQL has been stopped."
    fi
    exit 0
else
    # There are changes to migrations
    echo "Migrations are out of date. Please run 'pipenv run python manage.py makemigrations' and commit the changes."
    # If MySQL was not originally running, stop it before exiting
    if [ "$MYSQL_RUNNING" = false ]; then
        docker-compose stop db
        echo "MySQL has been stopped."
    fi
    exit 1
fi

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File checks/static.sh:

#!/bin/bash

# This script generates production-ready files for the scripts and styles
# It runs npm run build
# If files are changed then fails

# Exit on error
set -e

# Run npm run build
npm run build

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Use Pipenv to install some development dependencies

pipenv install --dev black==23.7.0 pre-commit==3.3.3 flake8==6.1.0 isort==5.12.0 tomli==2.0.1

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I've pinned the versions of the development dependencies to the same versions as the pre-commit hooks.

Install the pre-commit hooks

pipenv run pre-commit install

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You can use the pre-commit install command to initialize pre-commit. You can also run pre-commit uninstall to remove the hooks.

Run the pre-commit hooks

pipenv run pre-commit run --all-files

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If this is the first time running pre-commit you'll probably see some file changes have been made. You can commit these changes and then run the pre-commit hooks again to make sure everything is ok.

Commit the changes

git add .
git commit -m "add your commit message here"

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Having pre-commit installed means that every time you commit code, the pre-commit hooks will run and check your code.

If there are any errors, the commit will fail and you'll need to fix the errors before you can commit again.

Make sure you have stopped the npm server before you commit, the one you started with npm start.

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