RenameModel requires camel case model names

[Neil Parsons]

The migrations.RenameModel class appears to accept all lowercase model names but when the makemigrations command is run afterwards it will generate an AlterField migration every time. This occurs when there exists a model that has a ForeignKey that relies on the renamed model.

When the model names are changed to camel case the makemigrations command works as expected and no longer generates AlterField migrations.

Migration that will cause the error case:

migrations.RenameModel(
    old_name='originalmodel',  # Note: Not using CamelCase!
    new_name='renamedmodel',
),

The generated migration in the error case:

migrations.AlterField(
    model_name='anothermodel',
    name='foreign_key_field',
    field=models.ForeignKey(on_delete=django.db.models.deletion.CASCADE, to='an_app.RenamedModel'),
),

This behaviour can be seen in this demo project: ​https://github.com/npars/django-bad-migrations

[Tim Graham]

Probably the same cause as #23916.