UniqueConstraint rises fields.E310 error because of issue with backward compatibility with unique_together

[Pavel Garkin]

Hi all,

I'm trying to create migration with uniqueness of 2 fields: uid, source. 

Django 2.2.9

class Users(models.Model):
    uid = models.CharField(...)
    source = models.ForeignKey(...)

    class Meta:
       constraints = [models.UniqueConstraint(fields=['uid', 'source'], name='users_uniqueness')]
       indexes = [models.Index(fields=('uid', 'source'), name='users_indexes')]


When I start makemigrations command in manage.py it rises fields.E310 error

app_name.Users.field: (fields.E310) No subset of the fields 'uid', 'source' on model 'Users' is unique.
	HINT: Add unique=True on any of those fields or add at least a subset of them to a unique_together constraint.


When I change Meta options to unique_together constraint it works ok. Migrations passes with no errors

...
   class Meta:
        unique_together = [['uid', 'source']]

As mentioned in docs unique_together may be deprecated in the future so I wanted to avoid this kind of issue.


Thanks,
Pavel

[Simon Charette]

Hello Pavel,

This is likely a bug because UniqueConstraint was only recently introduced.

Please file a bug report about it. In the mean time you can add this check to

your SILENCED_SYSTEM_CHECKS setting to silence it.

Best,

Simon