Fix "NO FILE" Migrations in Rails

You may find yourself in the situation where running...

rails db:migrate:status

...and notice some entries that look like:

up     20230902123456  ********** NO FILE **********

It means that you switched to a branch with a migration in it, ran rails db:migrate, and then switched to another branch. The migration changed your database, but because you switched branches, the migration file is no longer in your code.

To correct this problem, you may try the following:

1. Find the branch that where the missing migration lives. Use this, replacing the timestamp in this example with the one from rails db:migrate:status.

git log --all -- '**/20230902123456*'

2. Switch to the branch that is returned with git checkout <branch>. (You may need to either commit or stash any unsaved local changes.)

3. Reverse the migration (if reversible) with the following (again, using the timestamp from status):

rails db:migrate:down VERSION=20230902123456

4. Abandon the change to the schema it just made with git checkout db\schema.rb.

5. Switch back to your original branch. If you used stash before, restore your stash with git stash pop.