[Django] #36146: Double-squashed migration is omitted from migration plan

[Django]

#36146: Double-squashed migration is omitted from migration plan
-----------------------------+-------------------------------------------
Reporter: Jacob Walls | Type: Bug
Status: new | Component: Migrations
Version: dev | Severity: Release blocker
Keywords: | Triage Stage: Unreviewed
Has patch: 0 | Needs documentation: 0
Needs tests: 0 | Patch needs improvement: 0
Easy pickings: 0 | UI/UX: 0
-----------------------------+-------------------------------------------
Start with this `models.py` and generate three simple migrations:
{{{#!python
from django.db import models

class A(models.Model):
foo = models.BooleanField()
}}}

{{{
./manage.py makemigrations
}}}

{{{#!python
from django.db import models

class A(models.Model):
foo = models.BooleanField(default=True)
}}}

{{{
./manage.py makemigrations
}}}

{{{#!python
from django.db import models

class A(models.Model):
foo = models.BooleanField(default=False)
}}}

{{{
./manage.py makemigrations
}}}

Migrate.
Squash, migrate, double-squash, migrate.
Migrate back to zero.
{{{
./manage.py migrate
./manage.py squashmigrations new 0001 0002
./manage.py migrate
./manage.py squashmigrations new 0001_initial_squashed 0003
./manage.py migrate
./manage.py migrate new zero
}}}

Now notice the forward plan is missing a migration:
{{{
./manage.py migrate
Operations to perform:
Apply all migrations: new
Running migrations:
Applying new.0003_alter_a_foo... OK
}}}

And reverse migrate fails (failure would have been evident in the last
step if it hadn't been an SQL noop):
{{{
./manage.py migrate new zero
Operations to perform:
Unapply all migrations: new
Running migrations:
Rendering model states... DONE
Unapplying
new.0001_initial_squashed_0002_alter_a_foo_squashed_0003_alter_a_foo...Traceback
(most recent call last):
File "/Users/jwalls/django/django/db/backends/utils.py", line 103, in
_execute
return self.cursor.execute(sql)
~~~~~~~~~~~~~~~~~~~^^^^^
psycopg2.errors.UndefinedTable: table "new_a" does not exist
}}}
--
Ticket URL: <https://code.djangoproject.com/ticket/36146>
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