id summary reporter owner description type status component version severity resolution keywords cc stage has_patch needs_docs needs_tests needs_better_patch easy ui_ux 33902 UniqueConstraint's validation crashes with string expressions. Adam Zahradník Mariusz Felisiak "When using UniqueConstraint with field names in `expressions` in Django 4.1, an error is raised when the model is saved: {{{ Traceback (most recent call last): File ""/usr/local/lib/python3.10/site-packages/django/core/handlers/exception.py"", line 55, in inner response = get_response(request) File ""/usr/local/lib/python3.10/site-packages/django/core/handlers/base.py"", line 197, in _get_response response = wrapped_callback(request, *callback_args, **callback_kwargs) File ""/usr/local/lib/python3.10/site-packages/django/contrib/admin/options.py"", line 686, in wrapper return self.admin_site.admin_view(view)(*args, **kwargs) File ""/usr/local/lib/python3.10/site-packages/django/utils/decorators.py"", line 133, in _wrapped_view response = view_func(request, *args, **kwargs) File ""/usr/local/lib/python3.10/site-packages/django/views/decorators/cache.py"", line 62, in _wrapped_view_func response = view_func(request, *args, **kwargs) File ""/usr/local/lib/python3.10/site-packages/django/contrib/admin/sites.py"", line 242, in inner return view(request, *args, **kwargs) File ""/usr/local/lib/python3.10/site-packages/django/contrib/admin/options.py"", line 1890, in add_view return self.changeform_view(request, None, form_url, extra_context) File ""/usr/local/lib/python3.10/site-packages/django/utils/decorators.py"", line 46, in _wrapper return bound_method(*args, **kwargs) File ""/usr/local/lib/python3.10/site-packages/django/utils/decorators.py"", line 133, in _wrapped_view response = view_func(request, *args, **kwargs) File ""/usr/local/lib/python3.10/site-packages/django/contrib/admin/options.py"", line 1750, in changeform_view return self._changeform_view(request, object_id, form_url, extra_context) File ""/usr/local/lib/python3.10/site-packages/django/contrib/admin/options.py"", line 1796, in _changeform_view form_validated = form.is_valid() File ""/usr/local/lib/python3.10/site-packages/django/forms/forms.py"", line 205, in is_valid return self.is_bound and not self.errors File ""/usr/local/lib/python3.10/site-packages/django/forms/forms.py"", line 200, in errors self.full_clean() File ""/usr/local/lib/python3.10/site-packages/django/forms/forms.py"", line 439, in full_clean self._post_clean() File ""/usr/local/lib/python3.10/site-packages/django/forms/models.py"", line 492, in _post_clean self.instance.full_clean(exclude=exclude, validate_unique=False) File ""/usr/local/lib/python3.10/site-packages/django/db/models/base.py"", line 1491, in full_clean self.validate_constraints(exclude=exclude) File ""/usr/local/lib/python3.10/site-packages/django/db/models/base.py"", line 1442, in validate_constraints constraint.validate(model_class, self, exclude=exclude, using=using) File ""/usr/local/lib/python3.10/site-packages/django/db/models/constraints.py"", line 329, in validate for expr in expression.flatten(): AttributeError: 'F' object has no attribute 'flatten' }}} The culprit is most probably the new constraint validation (call to self.validate_constraints in the traceback). This is excerpt from the model in question: {{{ class Model: class Meta: constraints = ( UniqueConstraint( ""field1"", ""field2"", name=""some_constraint_name"", ), ) }}} Please note, that I am not using the `fields` keyword argument, but the positional `expressions`. I can confirm that the same model works in Django 4.0.7." Bug closed Database layer (models, ORM) 4.1 Release blocker fixed Gagaro Accepted 1 0 0 0 0 0