[Django] #32697: Older versions of Django insist on converting BigAutoField back to AutoField

[Django]

#32697: Older versions of Django insist on converting BigAutoField back to
AutoField
---------------------------------------------+------------------------
Reporter: Alexander Todorov | Owner: nobody
Type: Bug | Status: new
Component: Migrations | Version: 3.2
Severity: Normal | Keywords:
Triage Stage: Unreviewed | Has patch: 0
Needs documentation: 0 | Needs tests: 0
Patch needs improvement: 0 | Easy pickings: 0
UI/UX: 0 |
---------------------------------------------+------------------------
I've added the following change to django-attachments:

{{{
class AttachmentsConfig(AppConfig):
+ default_auto_field = 'django.db.models.BigAutoField'
name = "attachments"
verbose_name = _("Attachments")
diff --git a/attachments/migrations/0006_alter_pk_to_BigAutoField.py
b/attachments/migrations/0006_alter_pk_to_BigAutoField.py
new file mode 100644
index 0000000..ab840dd
--- /dev/null
+++ b/attachments/migrations/0006_alter_pk_to_BigAutoField.py
@@ -0,0 +1,18 @@
+# Generated by Django 3.2 on 2021-04-27 20:18
+
+from django.db import migrations, models
+
+
+class Migration(migrations.Migration):
+
+ dependencies = [
+ ('attachments', '0005_object_id_charfield'),
+ ]
+
+ operations = [
+ migrations.AlterField(
+ model_name='attachment',
+ name='id',
+ field=models.BigAutoField(auto_created=True,
primary_key=True, serialize=False, verbose_name='ID'),
+
}}}

Since the release notes point out that in the future BigAutoField is to be
the default and that new apps are already generated with BigAutoField I've
decided to use that as the default value. The new migration will take care
of existing installations. Or so I thought.

In our test suite when running with Django < 3.2 (e.g. 3.1.8)
`makemigrations` insists on reverting this field back to AutoField and it
creates the following 3rd migration -
`attachments/migrations/0007_auto_20210429_0400.py`:

{{{
# Generated by Django 3.1.8 on 2021-04-29 04:00

from django.db import migrations, models

class Migration(migrations.Migration):

dependencies = [
('attachments', '0006_alter_pk_to_BigAutoField'),
]

operations = [
migrations.AlterField(
model_name='attachment',
name='id',
field=models.AutoField(auto_created=True, primary_key=True,
serialize=False, verbose_name='ID'),
),
]
}}}

I wasn't able to figure out how to prevent this from happening or what's
causing it but I see this as a problem.

For example a downstream app which is using django-attachments will call
`makemigrations` to adjust their own migrations at some point in time,
which will result in unwanted (and maybe even undetected) migrations for
django-attachments.

--
Ticket URL: <https://code.djangoproject.com/ticket/32697>
Django <https://code.djangoproject.com/>
The Web framework for perfectionists with deadlines.

[Django]

#32697: Older versions of Django insist on converting BigAutoField back to
AutoField

-----------------------------------+--------------------------------------

Reporter: Alexander Todorov | Owner: nobody

Type: Bug | Status: closed
Component: Migrations | Version: 3.2
Severity: Normal | Resolution: invalid

Keywords: | Triage Stage: Unreviewed
Has patch: 0 | Needs documentation: 0
Needs tests: 0 | Patch needs improvement: 0
Easy pickings: 0 | UI/UX: 0

-----------------------------------+--------------------------------------
Changes (by Mariusz Felisiak):

* status: new => closed
* resolution: => invalid

Comment:

> Since the release notes point out that in the future BigAutoField is to

be the default ...

First of all I would like to ensure you that this will not happen in the
nearest future (maybe never). I can not imagine that we would change that
before dropping support for all versions prior to 3.2.

> In our test suite when running with Django < 3.2 (e.g. 3.1.8)
makemigrations insists on reverting this field back to AutoField and it
creates the following 3rd migration -

attachments/migrations/0007_auto_20210429_0400.py:

That's because `AppConfig.default_auto_field` doesn't exist in Django <
3.1, so it cannot be taken into account.

I would recommend to keep `default_auto_field =
'django.db.models.AutoField'` until Django 3.2 becomes the minimal Django
supported by your package.

--
Ticket URL: <https://code.djangoproject.com/ticket/32697#comment:1>