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
36222	ExclusionConstraint.validate() crashes when exclude includes a field in condition.	Clifford Gama	JaeHyuckSa	"Discovered during work on #35676.

Failing test:

{{{#!diff
diff --git a/tests/postgres_tests/test_constraints.py b/tests/postgres_tests/test_constraints.py
index ab5bf2bab1..ae02fa22ff 100644
--- a/tests/postgres_tests/test_constraints.py
+++ b/tests/postgres_tests/test_constraints.py
@@ -797,6 +797,17 @@ class ExclusionConstraintTests(PostgreSQLTestCase):
             ),
             exclude={""datespan"", ""start"", ""end"", ""room""},
         )
+        # Excluded condition field.
+        constraint.validate(
+            HotelReservation,
+            HotelReservation(
+                datespan=(datetimes[1].date(), datetimes[2].date()),
+                start=datetimes[1],
+                end=datetimes[2],
+                room=room102,
+            ),
+            exclude={""cancelled""},
+        )
 
     def test_range_overlaps_custom(self):
         class TsTzRange(Func):
}}}
Results in two test failures. Here is the failure for one of the tests:
{{{#!python
======================================================================
ERROR: test_range_overlaps (postgres_tests.test_constraints.ExclusionConstraintTests.test_range_overlaps)
----------------------------------------------------------------------
Traceback (most recent call last):
  File ""/home/clifford/code/django/tests/postgres_tests/test_constraints.py"", line 839, in test_range_overlaps
    self._test_range_overlaps(constraint)
  File ""/home/clifford/code/django/tests/postgres_tests/test_constraints.py"", line 801, in _test_range_overlaps
    constraint.validate(
  File ""/home/clifford/code/django/django/contrib/postgres/constraints.py"", line 209, in validate
    if (self.condition & Exists(queryset.filter(self.condition))).check(
       ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
  File ""/home/clifford/code/django/django/db/models/query_utils.py"", line 137, in check
    query.add_q(Q(Coalesce(self, True, output_field=BooleanField())))
  File ""/home/clifford/code/django/django/db/models/sql/query.py"", line 1637, in add_q
    clause, _ = self._add_q(q_object, can_reuse)
                ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
  File ""/home/clifford/code/django/django/db/models/sql/query.py"", line 1669, in _add_q
    child_clause, needed_inner = self.build_filter(
                                 ^^^^^^^^^^^^^^^^^^
  File ""/home/clifford/code/django/django/db/models/sql/query.py"", line 1508, in build_filter
    condition = filter_expr.resolve_expression(
                ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
  File ""/home/clifford/code/django/django/db/models/expressions.py"", line 300, in resolve_expression
    expr.resolve_expression(query, allow_joins, reuse, summarize)
  File ""/home/clifford/code/django/django/db/models/query_utils.py"", line 91, in resolve_expression
    clause, joins = query._add_q(
                    ^^^^^^^^^^^^^
  File ""/home/clifford/code/django/django/db/models/sql/query.py"", line 1669, in _add_q
    child_clause, needed_inner = self.build_filter(
                                 ^^^^^^^^^^^^^^^^^^
  File ""/home/clifford/code/django/django/db/models/sql/query.py"", line 1517, in build_filter
    lookups, parts, reffed_expression = self.solve_lookup_type(arg, summarize)
                                        ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
  File ""/home/clifford/code/django/django/db/models/sql/query.py"", line 1324, in solve_lookup_type
    _, field, _, lookup_parts = self.names_to_path(lookup_splitted, self.get_meta())
                                ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
  File ""/home/clifford/code/django/django/db/models/sql/query.py"", line 1796, in names_to_path
    raise FieldError(
django.core.exceptions.FieldError: Cannot resolve keyword 'cancelled' into field. Choices are: _check
}}}

This works correctly for `UniqueConstraint` (see [https://github.com/django/django/blob/fc303551077c3e023fe4f9d01fc1b3026c816fa4/tests/constraints/tests.py#L1097 test]), but has been untested (or failure has been undocumented) for `ExclusionConstraint` since `Constraint` validation was added by #30581."	Bug	closed	Database layer (models, ORM)	dev	Normal	fixed	validate_constraints ExclusionConstraint exclude	Clifford Gama	Ready for checkin	1	0	0	0	0	0