Fixed #35103 -- Used provided error code and message when fields is set without a condition on UniqueConstraint.

1 files changed, 12 insertions, 4 deletions

diff --git a/django/db/models/constraints.py b/django/db/models/constraints.py
index 3859a60e2f..788e2b635b 100644
--- a/django/db/models/constraints.py
+++ b/django/db/models/constraints.py
@@ -690,11 +690,19 @@ class UniqueConstraint(BaseConstraint):
             queryset = queryset.exclude(pk=model_class_pk)
         if not self.condition:
             if queryset.exists():
-                if self.fields:
-                    # When fields are defined, use the unique_error_message() for
-                    # backward compatibility.
+                if (
+                    self.fields
+                    and self.violation_error_message
+                    == self.default_violation_error_message
+                ):
+                    # When fields are defined, use the unique_error_message() as
+                    # a default for backward compatibility.
+                    validation_error_message = instance.unique_error_message(
+                        model, self.fields
+                    )
                     raise ValidationError(
-                        instance.unique_error_message(model, self.fields),
+                        validation_error_message,
+                        code=validation_error_message.code,
                     )
                 raise ValidationError(
                     self.get_violation_error_message(),