add unique creation/deletion support to SchemaEditor.alter_field()

Author: timgraham

django_mongodb/features.py

@@ -90,15 +90,10 @@ class DatabaseFeatures(BaseDatabaseFeatures):
         # AlterField
         "schema.tests.SchemaTests.test_alter_auto_field_to_integer_field",
         "schema.tests.SchemaTests.test_alter_field_default_dropped",
-        "schema.tests.SchemaTests.test_alter_field_fk_to_o2o",
-        "schema.tests.SchemaTests.test_alter_field_o2o_to_fk",
         "schema.tests.SchemaTests.test_alter_null_to_not_null",
         "schema.tests.SchemaTests.test_alter_primary_key_the_same_name",
         "schema.tests.SchemaTests.test_autofield_to_o2o",
         "schema.tests.SchemaTests.test_remove_constraints_capital_letters",
-        # AlterField (unique)
-        "schema.tests.SchemaTests.test_indexes",
-        "schema.tests.SchemaTests.test_unique",
     }
     # $bitAnd, #bitOr, and $bitXor are new in MongoDB 6.3.
     _django_test_expected_failures_bitwise = {

django_mongodb/schema.py

@@ -86,6 +86,30 @@ def _alter_field(
         new_db_params,
         strict=False,
     ):
+        # Has unique been removed?
+        if old_field.unique and (
+            not new_field.unique or self._field_became_primary_key(old_field, new_field)
+        ):
+            # Find the unique constraint for this field
+            meta_constraint_names = {constraint.name for constraint in model._meta.constraints}
+            constraint_names = self._constraint_names(
+                model,
+                [old_field.column],
+                unique=True,
+                primary_key=False,
+                exclude=meta_constraint_names,
+            )
+            if strict and len(constraint_names) != 1:
+                raise ValueError(
+                    f"Found wrong number ({len(constraint_names)}) of unique "
+                    f"constraints for {model._meta.db_table}.{old_field.column}"
+                )
+            for constraint_name in constraint_names:
+                constraint = UniqueConstraint(
+                    fields=[old_field.name],
+                    name=constraint_name,
+                )
+                self.remove_constraint(model, constraint)
         # Removed an index? (no strict check, as multiple indexes are possible)
         # Remove indexes if db_index switched to False or a unique constraint
         # will now be used in lieu of an index. The following lines from the
@@ -122,6 +146,25 @@ def _alter_field(
             self.connection.database[model._meta.db_table].update_many(
                 {}, {"$rename": {old_field.column: new_field.column}}
             )
+            # Rename index
+            if old_field.db_index and new_field.db_index:
+                pass
+            # Rename unique
+            if old_field.unique and new_field.unique:
+                old_constraint = UniqueConstraint(
+                    fields=[old_field.name], name=f"{model._meta.db_table}_{old_field.column}_key"
+                )
+                self.add_constraint(model, old_constraint)
+                new_constraint = UniqueConstraint(
+                    fields=[new_field.name], name=f"{model._meta.db_table}_{new_field.column}_key"
+                )
+                self.add_constraint(model, new_constraint, field=new_field)
+        # Added a unique?
+        if self._unique_should_be_added(old_field, new_field):
+            constraint = UniqueConstraint(
+                fields=[new_field.name], name=f"{model._meta.db_table}_{new_field.column}_key"
+            )
+            self.add_constraint(model, constraint)
         # Added an index? Add an index if db_index switched to True or a unique
         # constraint will no longer be used in lieu of an index. The following
         # lines from the truth table show all True cases; the rest are False: