Migration's ModelState has varying type for unique_together and index_together options causing autodetector crash

[Markus Holtermann]

When leveraging the MigrationAutodetector to get the changes between two project states, the following exception is raised (on 5.2, but the same applies to the current master at commit b1ffa9a9d78b0c2c5ad6ed5a1d84e380d5cfd010):

Traceback (most recent call last):
  File "<frozen runpy>", line 198, in _run_module_as_main
  File "<frozen runpy>", line 88, in _run_code
  File "src/manage.py", line 67, in <module>
    management.execute_from_command_line(sys.argv)
    ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~^^^^^^^^^^
  File ".venv/lib/python3.13/site-packages/django/core/management/__init__.py", line 442, in execute_from_command_line
    utility.execute()
    ~~~~~~~~~~~~~~~^^
  File ".venv/lib/python3.13/site-packages/django/core/management/__init__.py", line 436, in execute
    self.fetch_command(subcommand).run_from_argv(self.argv)
    ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~^^^^^^^^^^^
  File ".venv/lib/python3.13/site-packages/django/core/management/base.py", line 420, in run_from_argv
    self.execute(*args, **cmd_options)
    ~~~~~~~~~~~~^^^^^^^^^^^^^^^^^^^^^^
  File ".venv/lib/python3.13/site-packages/django/core/management/base.py", line 464, in execute
    output = self.handle(*args, **options)
  File "src/core/management/commands/some_command.py", line 94, in handle
    self._get_migrations_and_operations(section)
    ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~^^^^^^^^^
  File "src/core/management/commands/some_command.py", line 238, in _get_migrations_and_operations
    new_migrations = autodetector.changes(self.graph, trim_to_apps={"affiliates"})
  File ".venv/lib/python3.13/site-packages/django/db/migrations/autodetector.py", line 67, in changes
    changes = self._detect_changes(convert_apps, graph)
  File ".venv/lib/python3.13/site-packages/django/db/migrations/autodetector.py", line 213, in _detect_changes
    self.generate_removed_altered_unique_together()
    ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~^^
  File ".venv/lib/python3.13/site-packages/django/db/migrations/autodetector.py", line 1718, in generate_removed_altered_unique_together
    self._generate_removed_altered_foo_together(operations.AlterUniqueTogether)
    ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
  File ".venv/lib/python3.13/site-packages/django/db/migrations/autodetector.py", line 1699, in _generate_removed_altered_foo_together
    ) in self._get_altered_foo_together_operations(operation.option_name):
         ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~^^^^^^^^^^^^^^^^^^^^^^^
  File ".venv/lib/python3.13/site-packages/django/db/migrations/autodetector.py", line 1668, in _get_altered_foo_together_operations
    new_value = set(new_value) if new_value else set()
                ~~~^^^^^^^^^^^
TypeError: unhashable type: 'list'

Reason:

The migration ModelState tracks the changes for all options (order_with_respect_to, unique_together, indexes, ...) in its options attribute, which is a simple dict. For most keys inside the dict, the value is just a list of something. However, for unique_together and index_together, the value should be a set of tuples (​see the ModelState.from_model() method).

Unfortunately, there are situations inside the ProjectState's mutation functions (​e.g. rename_field()) where the data type for model_state.options["unique_together"] is changed to list[list[str]]:

        for option in ("index_together", "unique_together"):
            if option in options:
                options[option] = [
                    [new_name if n == old_name else n for n in together]
                    for together in options[option]
                ]