django-migration-fixer 0.0.2

Resolve migration errors

django-migration-fixer

Problem

Maintain a linear migration history when conflicts occur as a result of changes made using different versions of the default branch.

Example

Branch: main

migrations
  ├── 0001_initial.py
  ├── 0002_auto_20210521_2328.py 

Branch: feature/test-a

migrations
  ├── 0001_initial.py
  ├── 0002_auto_20210521_2328.py
  ├── 0003_auto_20210522_1128.py 

Branch:feature/test-b

migrations
  ├── 0001_initial.py
  ├── 0002_auto_20210521_2328.py
  ├── 0003_auto_20210522_1228.py 

Both feature/test-a and feature/test-b share the last migration on main (0002_auto_20210521_2328.py)

Once feature/test-a is merged into main you run into the problem of resolving migrations on feature/test-b which was dependent on 0002_auto_20210521_2328.py

Branch: main

migrations
  ├── 0001_initial.py
  ├── 0002_auto_20210521_2328.py
  ├── 0003_auto_20210522_1128.py 

Branch: feature/test-b

migrations
  ├── 0001_initial.py
  ├── 0002_auto_20210521_2328.py
  ├── 0003_auto_20210522_1128.py \___________________ Both dependent on 0002_auto_20210521_2328.py
  ├── 0003_auto_20210522_1228.py /

Error running makemigrations

CommandError: Conflicting migrations detected; multiple leaf nodes in the migration graph: (0003_auto_20210522_1128, 0003_auto_20210522_1228 in my_app).
To fix them run 'python manage.py makemigrations --merge'

Using the default --merge option creates a new migration file which might not be desired.

Solution

django-migration-fixer identifies changes between the default branch main, and the feature branch feature/test-b and maintains a linear dependency history as shown below:

Run

$ python manage.py makemigrations --fix

Branch: feature/test-b

migrations
  ├── 0001_initial.py
  ├── 0002_auto_20210521_2328.py
  ├── 0003_auto_20210522_1128.py
  ├── 0004_auto_20210522_1228.py

NOTE: This also works when there are conflicts detected on the default branch. i.e You can run ... makemigrations --fix on the main branch.

Assumptions

The final migration on the default branch would be used as the base for all subsequent migrations.

Installation

$ pip install django-migration-fixer

Add migration_fixer to your INSTALLED_APPS

INSTALLED_APPS = [
    ...,
    "migration_fixer",
    ...,
]

Usage

$ python manage.py makemigrations --fix 

Specifying a different default branch name

Use:

$ python manage.py makemigrations -b master --fix 

Features

• Resolves migration conflicts on both the default branch or feature/PR branches
• Supports numbered migration files i.e (0001_....py)
• Supports non-numbered migration files i.e (custom_migration.py)
• Re-index all migrations using the last migration on the default branch i.e main