Create a standard pre-commit hook to require safe attribute

[tim-schilling]

We wrote a simple regex pre-commit hook that's extremely crude. It works well enough for us, but the library should probably have something a bit better.

"""
Search our application's migrations are using django_safemigrate.

This is fairly rudimentary and won't work if the class doesn't explicitly inherit
from ``Migration``.
"""

import os
import re
import sys

MIGRATION_PATTERN = re.compile(r"class\s+(?P<MigrationClass>\w+)\s?\(.*Migration\):")
MIGRATION_FILE_PATTERN = re.compile(r"^\d{4}_.+\.py$")

MISSING_SAFE_MESSAGE = (
    "{file_path}: {migration_class} is missing the 'safe' attribute.\n"
)
FAILURE_MESSAGE = (
    "\n"
    "Add the following to the migration class:\n"
    "from django_safemigrate import Safe"
    "class Migration(migrations.Migration):\n"
    "    safe = Safe.before_deploy\n"
    "\n"
    "You can also use the following:\n"
    "    safe = Safe.always\n"
    "    safe = Safe.after_deploy\n"
)


def find_migration_files(directory):
    for root, _, files in os.walk(directory):
        for file in files:
            file_is_migration = MIGRATION_FILE_PATTERN.match(file)
            if file_is_migration and file.endswith(".py"):
                yield os.path.join(root, file)


def validate_migrations():
    success = True
    for file_path in find_migration_files("."):
        # Strip the leading ./ it's a byproduct of os.walk on the current directory
        file_path = file_path[2:] if file_path.startswith("./") else file_path
        with open(file_path, "r") as f:
            content = f.read()

        match = MIGRATION_PATTERN.search(content)
        if match:
            migration_class = match.group("MigrationClass")
            if "safe = Safe." not in content:
                success = False
                sys.stdout.write(
                    MISSING_SAFE_MESSAGE.format(
                        file_path=file_path, migration_class=migration_class
                    )
                )
    if not success:
        sys.stdout.write(FAILURE_MESSAGE)
    return success


if __name__ == "__main__":
    if not validate_migrations():
        sys.exit(1)

Then in the yaml:

repos:
  - repo: local
    hooks:
    -   id: require-safe-migrations
        name: Require migrations to use django_safemigrate
        entry: python -m devops.linters.require_safe_migrations
        language: system
        pass_filenames: false

[ryanhiebert]

This is great, and I think that this would be worthwhile to include even in its crude state. It's sufficient for my purposes. If people find it too finnicky, we'll be happy for contributions to fix that up, otherwise it'll solve a very common problem in an obvious way.