[3.1.x] Refs #32096 -- Fixed ExclusionConstraint crash with JSONField key transforms in expressions.

Regression in 6789ded0a6ab797f0dcdfa6ad5d1cfa46e23abcd.

Backport of ee0abac169c2dcc6818d583247903c2a8ef55f7c from master.

5 files changed, 30 insertions, 4 deletions

diff --git a/django/contrib/postgres/constraints.py b/django/contrib/postgres/constraints.py
index aea1f9bb3d..038840990b 100644
--- a/django/contrib/postgres/constraints.py
+++ b/django/contrib/postgres/constraints.py
@@ -45,14 +45,15 @@ class ExclusionConstraint(BaseConstraint):
         self.deferrable = deferrable
         super().__init__(name=name)
 
-    def _get_expression_sql(self, compiler, connection, query):
+    def _get_expression_sql(self, compiler, schema_editor, query):
         expressions = []
         for expression, operator in self.expressions:
             if isinstance(expression, str):
                 expression = F(expression)
             expression = expression.resolve_expression(query=query)
-            sql, params = expression.as_sql(compiler, connection)
-            expressions.append('%s WITH %s' % (sql % params, operator))
+            sql, params = compiler.compile(expression)
+            sql = sql % tuple(schema_editor.quote_value(p) for p in params)
+            expressions.append('%s WITH %s' % (sql, operator))
         return expressions
 
     def _get_condition_sql(self, compiler, schema_editor, query):
@@ -65,7 +66,7 @@ class ExclusionConstraint(BaseConstraint):
     def constraint_sql(self, model, schema_editor):
         query = Query(model, alias_cols=False)
         compiler = query.get_compiler(connection=schema_editor.connection)
-        expressions = self._get_expression_sql(compiler, schema_editor.connection, query)
+        expressions = self._get_expression_sql(compiler, schema_editor, query)
         condition = self._get_condition_sql(compiler, schema_editor, query)
         return self.template % {
             'name': schema_editor.quote_name(self.name),
diff --git a/docs/releases/3.1.3.txt b/docs/releases/3.1.3.txt
index e6c13fff40..8c7b533b48 100644
--- a/docs/releases/3.1.3.txt
+++ b/docs/releases/3.1.3.txt
@@ -33,3 +33,9 @@ Bugfixes
 * Fixed a regression in Django 3.1 that caused a crash of
   :class:`~django.db.models.ExpressionWrapper` with key transforms for
   :class:`~django.db.models.JSONField` (:ticket:`32096`).
+
+* Fixed a regression in Django 3.1 that caused a migrations crash on PostgreSQL
+  when adding an
+  :class:`~django.contrib.postgres.constraints.ExclusionConstraint` with key
+  transforms for :class:`~django.db.models.JSONField` in ``expressions``
+  (:ticket:`32096`).
diff --git a/tests/postgres_tests/migrations/0002_create_test_models.py b/tests/postgres_tests/migrations/0002_create_test_models.py
index e334057d22..cd8b20ae01 100644
--- a/tests/postgres_tests/migrations/0002_create_test_models.py
+++ b/tests/postgres_tests/migrations/0002_create_test_models.py
@@ -303,6 +303,7 @@ class Migration(migrations.Migration):
                 ('start', models.DateTimeField()),
                 ('end', models.DateTimeField()),
                 ('cancelled', models.BooleanField(default=False)),
+                ('requirements', models.JSONField(blank=True, null=True)),
             ],
             options={
                 'required_db_vendor': 'postgresql',
diff --git a/tests/postgres_tests/models.py b/tests/postgres_tests/models.py
index a5bfc72fe7..56c81064f3 100644
--- a/tests/postgres_tests/models.py
+++ b/tests/postgres_tests/models.py
@@ -191,3 +191,4 @@ class HotelReservation(PostgreSQLModel):
     start = models.DateTimeField()
     end = models.DateTimeField()
     cancelled = models.BooleanField(default=False)
+    requirements = models.JSONField(blank=True, null=True)
diff --git a/tests/postgres_tests/test_constraints.py b/tests/postgres_tests/test_constraints.py
index 4c2e04705d..35bde7ba06 100644
--- a/tests/postgres_tests/test_constraints.py
+++ b/tests/postgres_tests/test_constraints.py
@@ -3,6 +3,7 @@ from unittest import mock
 
 from django.db import IntegrityError, connection, transaction
 from django.db.models import CheckConstraint, Deferrable, F, Func, Q
+from django.db.models.fields.json import KeyTextTransform
 from django.utils import timezone
 
 from . import PostgreSQLTestCase
@@ -397,6 +398,22 @@ class ExclusionConstraintTests(PostgreSQLTestCase):
             editor.remove_constraint(RangesModel, constraint)
         self.assertNotIn(constraint_name, self.get_constraints(RangesModel._meta.db_table))
 
+    def test_expressions_with_key_transform(self):
+        constraint_name = 'exclude_overlapping_reservations_smoking'
+        constraint = ExclusionConstraint(
+            name=constraint_name,
+            expressions=[
+                (F('datespan'), RangeOperators.OVERLAPS),
+                (KeyTextTransform('smoking', 'requirements'), RangeOperators.EQUAL),
+            ],
+        )
+        with connection.schema_editor() as editor:
+            editor.add_constraint(HotelReservation, constraint)
+        self.assertIn(
+            constraint_name,
+            self.get_constraints(HotelReservation._meta.db_table),
+        )
+
     def test_range_adjacent_initially_deferred(self):
         constraint_name = 'ints_adjacent_deferred'
         self.assertNotIn(constraint_name, self.get_constraints(RangesModel._meta.db_table))