CreateModel allows duplicate field names

[w0rp]

I hit this bug while manually editing a migration file after squashing files. If you define the same field twice in a list of fields for CreateModel, then migrate will take the second field definition without reporting any errors.

class Migration(migrations.Migration):
    operations = [
        migrations.CreateModel(
            name='Foo',
            fields=[
                ('id', models.AutoField(verbose_name='ID', serialize=False, auto_created=True, primary_key=True)),
                ('created', models.DateTimeField(auto_now_add=True, db_index=True)),
                # This one will be used.
                ('created', models.DateField(auto_now_add=True, db_index=True)),
            ],
        ),
    ]

I think the migration code should check for duplicate fields, and then report an error if you have mistakenly defined the same field twice for the fields array.

[Tim Graham]

Probably wouldn't hurt.

[Tim Graham]

​PR

[Markus Holtermann]

I don't know if we really need this check, but if we do that, the manager names need to be unique and so do the base classes.

[Simon Charette <charettes@…>]

In 417e083e:

Fixed #26521 -- Validated CreateModel bases, fields and managers for duplicates.

[Simon Charette <charettes@…>]

In a877a2f8:

Refs #26521 -- Added the duplicated value to CreateModel validation messages.

Thanks Tim for the suggestion.

[Collin Anderson]

I think this broke non-model base classes:

  File "/home/collin/comcenter/../comcenter/category/migrations/0001_initial.py", line 9, in <module>
    class Migration(migrations.Migration):
  File "/home/collin/comcenter/../comcenter/category/migrations/0001_initial.py", line 35, in Migration
    bases=(models.Model, comcenter.product.models.WhiteBlackListMixin),
  File "/home/collin/comcenter/django/db/migrations/operations/models.py", line 62, in __init__
    for base in self.bases
  File "/home/collin/comcenter/django/db/migrations/operations/models.py", line 17, in _check_for_duplicates
    for val in objs:
  File "/home/collin/comcenter/django/db/migrations/operations/models.py", line 63, in <genexpr>
    if base is not models.Model)
AttributeError: type object 'WhiteBlackListMixin' has no attribute 'lower'

[Simon Charette]

Will take care of this. I'm a bit surprised CreateModel is untested with mixins.

[Simon Charette <charettes@…>]

In f951bb78:

Refs #26521 -- Adjusted CreateModel bases validation to account for mixins.

Thanks Collin for the report.