[5.0.x] Fixed #35329 -- Fixed migrations crash when adding partial unique constraints with nulls_distinct.

Bug in 595a2abb58e04caa4d55fb2589bb80fb2a8fdfa1.

Thanks Lucas Lemke Saunitti for the report.
Backport of b98271a6e42107233311d17f5d7bc74fbb47f22c from main

1 files changed, 32 insertions, 0 deletions

diff --git a/tests/schema/tests.py b/tests/schema/tests.py
index 465245e3e7..fff4982315 100644
--- a/tests/schema/tests.py
+++ b/tests/schema/tests.py
@@ -3596,6 +3596,38 @@ class SchemaTests(TransactionTestCase):
         constraints = self.get_constraints(Author._meta.db_table)
         self.assertNotIn(constraint.name, constraints)
 
+    @skipUnlessDBFeature(
+        "supports_nulls_distinct_unique_constraints",
+        "supports_partial_indexes",
+    )
+    def test_unique_constraint_nulls_distinct_condition(self):
+        with connection.schema_editor() as editor:
+            editor.create_model(Author)
+        constraint = UniqueConstraint(
+            fields=["height", "weight"],
+            name="un_height_weight_start_A",
+            condition=Q(name__startswith="A"),
+            nulls_distinct=False,
+        )
+        with connection.schema_editor() as editor:
+            editor.add_constraint(Author, constraint)
+        Author.objects.create(name="Adam", height=None, weight=None)
+        Author.objects.create(name="Avocado", height=1, weight=None)
+        Author.objects.create(name="Adrian", height=None, weight=1)
+        with self.assertRaises(IntegrityError):
+            Author.objects.create(name="Alex", height=None, weight=None)
+        Author.objects.create(name="Bob", height=None, weight=None)
+        with self.assertRaises(IntegrityError):
+            Author.objects.create(name="Alex", height=1, weight=None)
+        Author.objects.create(name="Bill", height=None, weight=None)
+        with self.assertRaises(IntegrityError):
+            Author.objects.create(name="Alex", height=None, weight=1)
+        Author.objects.create(name="Celine", height=None, weight=1)
+        with connection.schema_editor() as editor:
+            editor.remove_constraint(Author, constraint)
+        constraints = self.get_constraints(Author._meta.db_table)
+        self.assertNotIn(constraint.name, constraints)
+
     @skipIfDBFeature("supports_nulls_distinct_unique_constraints")
     def test_unique_constraint_nulls_distinct_unsupported(self):
         # UniqueConstraint is ignored on databases that don't support