Fixed #35594 -- Added unique nulls distinct validation for expressions.

Thanks Mark Gensler for the report.

1 files changed, 8 insertions, 4 deletions

diff --git a/django/db/models/constraints.py b/django/db/models/constraints.py
index 9bb407274c..0a63e38d83 100644
--- a/django/db/models/constraints.py
+++ b/django/db/models/constraints.py
@@ -8,7 +8,7 @@ from django.db import connections
 from django.db.models.constants import LOOKUP_SEP
 from django.db.models.expressions import Exists, ExpressionList, F, RawSQL
 from django.db.models.indexes import IndexExpression
-from django.db.models.lookups import Exact
+from django.db.models.lookups import Exact, IsNull
 from django.db.models.query_utils import Q
 from django.db.models.sql.query import Query
 from django.db.utils import DEFAULT_DB_ALIAS
@@ -642,12 +642,16 @@ class UniqueConstraint(BaseConstraint):
                     meta=model._meta, exclude=exclude
                 ).items()
             }
-            expressions = []
+            filters = []
             for expr in self.expressions:
                 if hasattr(expr, "get_expression_for_validation"):
                     expr = expr.get_expression_for_validation()
-                expressions.append(Exact(expr, expr.replace_expressions(replacements)))
-            queryset = queryset.filter(*expressions)
+                rhs = expr.replace_expressions(replacements)
+                condition = Exact(expr, rhs)
+                if self.nulls_distinct is False:
+                    condition = Q(condition) | Q(IsNull(expr, True), IsNull(rhs, True))
+                filters.append(condition)
+            queryset = queryset.filter(*filters)
         model_class_pk = instance._get_pk_val(model._meta)
         if not instance._state.adding and model_class_pk is not None:
             queryset = queryset.exclude(pk=model_class_pk)