Removing unique_together constraint from model fails

[Stephen Burrows]

This actually fails in two places. In both cases, it is because unique_together is being set to None, and things expect it to be a list.

First, in trying to create the migration.

# django/django/db/migrations/operations/models.py, line 251
# This fails
return "Alter %s for %s (%s constraint(s))" % (self.option_name, self.name, len(self.unique_together))

# Should be
return "Alter %s for %s (%s constraint(s))" % (self.option_name, self.name, len(self.unique_together) if self.unique_together is not None else 0)

Second, in trying to *run* the migration (if you fix the first issue or manually create a migration.

# django/django/db/migrations/state.py, line 276
# This fails
meta_contents["unique_together"] = list(meta_contents["unique_together"])

# Should be
meta_contents["unique_together"] = list(meta_contents["unique_together"]) if meta_contents["unique_together"] is not None else None

[Tim Graham]

Still need to add a test for changes to state.py

[Tim Graham]

Will try to finish tomorrow if no one beats me to it.

[Tim Graham]

​PR

[Tim Graham <timograham@…>]

In 015496539247b24c73b163f279ae8c8d3ccefc4c:

Fixed #23013 -- Fixed removing unique_together/index_together constraints in migrations.

Thanks melinath for the report.

[Tim Graham <timograham@…>]

In 01515ebaa45a7facc6b450f3fea77dcdbec85887:

[1.7.x] Fixed #23013 -- Fixed removing unique_together/index_together constraints in migrations.

Thanks melinath for the report.

Backport of 0154965392 from master