django-migration-resolver-hook 0.1.4

Resolve migration conflicts.

django-migration-resolver-hook

Django Migration resolver ensures that migration files always stays ordered regardless of remote changes.

Problem:

With generated migration files using Django's manage.py makemigrations command you could run into issues where the generated migration files would potentially be out of sync with remote's master/default branch most CI servers are able to catch this error by running a test based on your local branch merge back into the base branch there by spotting duplicate migration nodes.

Solution:

This package aims to solve this problem by using a Doubly Linked List while traversing the app's migration file(s) to store and detect duplicate node(s) and potential conflicts.

When duplicate nodes are detected stat.st_mtime is used to sort files based on the last modified time.

:warning: This is not always accurate and might require a manual check to validate changes.

NOTE: This doesn't require Django's installed apps concept when using CLI commands since this is totally file based and should be executed within the root/app folders.

Table of Contents

1. Installation

2. Usage

   i. Use Case

   ii. Using Auto migration resolver

   iii. Using Static migration resolver

Installation

$ pip install django-migration-resolver-hook

Poetry

poetry add -D django-migration-resolver-hook

Usage

Use Case

Remote

|--- migrations
       |---- ...
       |---- 0007_auto_20200112_2328.py # Shared between remote and local repo
       |---- 0008_auto_20200113_4328.py # Only exists on remote
       |---- 0009_auto_20200114_4532.py
       |---- 0010_auto_20200115_1632.py

Local repo

|--- migrations
       |---- ...
       |---- 0007_auto_20200112_2328.py  # Shared between remote and local repo
       |---- 0008_auto_20200114_5438.py  # Only exists locally which raises duplicate migration nodes errors.

Since this is now out of sync with the remote branch to sync changes:

---

Using Auto migration resolver

---

CLI command: auto_migration_resolver

Auto detect and fix migration files by providing the following:

• --app-name: The app_name of the Django application.
• --strategy: The strategy used to resolve migration errors (options: "reseed"/"inline"). (Defaults to: "reseed")
• --exclude: The list of migration files that should be ignored.
• --commit: Perform a git commit for the changes after moving file old -> new.
• --verbose: Verbose command execution.

Usage:

$ auto_migration_resolver --app-name my_app --commit --verbose

Output

...

---

Using Static migration resolver

---

CLI command: migration_resolver

Fix migrations by providing the following:

• --app-name: The app_name of the Django application.
• --last: Last migration file of the remote that should be the seed of the conflicted migrations with or without the suffix.
• --conflict: The migration file which needs to be reseeded from the last migration file.
• --commit: Perform a git commit for the changes after moving file old -> new.
• --verbose: Verbose command execution.

Usage:

$ migration_resolver --app-name my_app --last 0010_auto_20200115_1632 --conflict 0008_auto_20200114_5438 --commit --verbose

Output

Fixing migrations...
Updating the conflicting migration file 0008_auto_20200114_5438.py
Succefully updated: 0008_auto_20200114_5438.py.
Renaming the migration file from 0008_auto_20200114_5438.py to 0011_auto_20200114_5438.py
Successfully renamed the migration file.
[my-test-branch c18fca41e] Resolved migration conflicts for 0008_auto_20200114_5438.py → 0011_auto_20200114_5438.py
1 file changed, 1 insertion(+), 1 deletion(-)
rename my_app/migrations/{0008_auto_20200114_5438.py => 0011_auto_20200114_5438.py} (99%)

For more options

$ migration_resolver --help

usage: migration_resolver [-h] [--auto-detect] [--verbose] --app-name APP_NAME --last LAST --conflict CONFLICT [--commit]

Resolve duplicate migration nodes.

optional arguments:
  -h, --help           show this help message and exit
  --auto-detect        Auto-detect and fix migration errors. (Not supported)
  --verbose            Verbose output
  --app-name APP_NAME  App Name
  --last LAST          The glob/full name of the final migration file.
  --conflict CONFLICT  The glob/full name of the final migration file with the conflict.
  --commit             Commit the changes made.

Using vsc (git/mercurial) when the remote has a migration files that conflict with previous migrations you have locally.

TODO:

• Auto detect and resolve errors with migration nodes.
• Speed up execution using async/await for handling reading nodes.
• Add support for database unapply migration for case of applied migrations.
• Add support to rollback any changes if there are failures in the chain of operation.
• VCS support right now only git is supported (extend to mercurial).
• Document Auto migration strategies.