Migration dependency not added when field is altered

[Erin Masatsugu]

If I have this a model in app A:

class AppAModel(models.Model):

    name = models.CharField(max_length=50, default="")

and this model in app B:

class AppBModel(models.Model):

    name = models.CharField(max_length=50, default="")

and a I add a foreign key to AppAModel in app C:

class AppCModel(models.Model):

    my_field = models.ForeignKey(AppAModel, on_delete=models.CASCADE)

the generated migration file correctly adds a dependency from app C to app A:

class Migration(migrations.Migration):

    dependencies = [

        ('app_a', 'XXXX_app_a_migration'),

        ('app_c', 'XXXX_app_c_migration'),

    ]

    operations = [

        migrations.CreateModel(

            name='AppCModel',

            fields=[

                ('id', models.AutoField(auto_created=True, primary_key=True, serialize=False, verbose_name='ID')),

                ('my_field', models.ForeignKey(on_delete=django.db.models.deletion.CASCADE, to='ncm.AppAModel')),

            ],

        ),

    ]

However, if I then update my_field to instead have a foreign key to AppBModel, django doesn't add a migration dependency from app C to app B:

class Migration(migrations.Migration):

    dependencies = [

        ('app_c', 'XXXX_app_c_migration'),

    ]

    operations = [

        migrations.AlterField(

            model_name='appcmodel',

            name='my_field',

            field=models.ForeignKey(on_delete=django.db.models.deletion.CASCADE, to='metals.AppBModel'),

        ),

    ]

I saw the response here https://groups.google.com/forum/#!searchin/django-users/migration$20dependency%7Csort:date/django-users/-h9LZxFomLU/ry_yeWGfDQAJ so I don't believe this is expected behavior, but can someone confirm?

Thank you!

Erin

[Durai pandian]

When you make any changes to the field, AlterField will be added rather than AddField.

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[Erin Masatsugu]

I understand that -- my question is why the AlterField operation in this case didn't add a migration dependency.

On Wednesday, May 27, 2020 at 6:44:16 PM UTC-10, Durai pandian wrote:

When you make any changes to the field, AlterField will be added rather than AddField.

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