[3.1.x] Refs #32096 -- Fixed crash of ArrayAgg/StringAgg/JSONBAgg with ordering over JSONField key transforms.

Regression in 6789ded0a6ab797f0dcdfa6ad5d1cfa46e23abcd.

Thanks Igor Jerosimić for the report.

Backport of 1f31027bb3ad460864fbcbbb89eeb328c0a2f184 from master

3 files changed, 28 insertions, 2 deletions

diff --git a/django/contrib/postgres/aggregates/mixins.py b/django/contrib/postgres/aggregates/mixins.py
index 2ab9052467..f2ba5c4439 100644
--- a/django/contrib/postgres/aggregates/mixins.py
+++ b/django/contrib/postgres/aggregates/mixins.py
@@ -24,7 +24,7 @@ class OrderableAggMixin:
             ordering_params = []
             ordering_expr_sql = []
             for expr in self.ordering:
-                expr_sql, expr_params = expr.as_sql(compiler, connection)
+                expr_sql, expr_params = compiler.compile(expr)
                 ordering_expr_sql.append(expr_sql)
                 ordering_params.extend(expr_params)
             sql, sql_params = super().as_sql(compiler, connection, ordering=(
diff --git a/docs/releases/3.1.3.txt b/docs/releases/3.1.3.txt
index 38062d4eed..8bc4877a0c 100644
--- a/docs/releases/3.1.3.txt
+++ b/docs/releases/3.1.3.txt
@@ -20,3 +20,8 @@ Bugfixes
   :class:`forms.JSONField <django.forms.JSONField>` and read-only
   :class:`models.JSONField <django.db.models.JSONField>` values in the admin
   (:ticket:`32080`).
+
+* Fixed a regression in Django 3.1 that caused a crash of
+  :class:`~django.contrib.postgres.aggregates.ArrayAgg` and
+  :class:`~django.contrib.postgres.aggregates.StringAgg` with ``ordering``
+  on key transforms for :class:`~django.db.models.JSONField` (:ticket:`32096`).
diff --git a/tests/postgres_tests/test_aggregates.py b/tests/postgres_tests/test_aggregates.py
index 8963ddbcf1..12f2a38e71 100644
--- a/tests/postgres_tests/test_aggregates.py
+++ b/tests/postgres_tests/test_aggregates.py
@@ -1,7 +1,7 @@
 import json
 
 from django.db.models import CharField, F, OuterRef, Q, Subquery, Value
-from django.db.models.fields.json import KeyTransform
+from django.db.models.fields.json import KeyTextTransform, KeyTransform
 from django.db.models.functions import Cast, Concat, Substr
 from django.test.utils import Approximate
 
@@ -106,6 +106,16 @@ class TestGeneralAggregate(PostgreSQLTestCase):
         )
         self.assertEqual(values, {'arrayagg': ['pl', 'en']})
 
+    def test_array_agg_jsonfield_ordering(self):
+        values = AggregateTestModel.objects.aggregate(
+            arrayagg=ArrayAgg(
+                KeyTransform('lang', 'json_field'),
+                filter=Q(json_field__lang__isnull=False),
+                ordering=KeyTransform('lang', 'json_field'),
+            ),
+        )
+        self.assertEqual(values, {'arrayagg': ['en', 'pl']})
+
     def test_array_agg_filter(self):
         values = AggregateTestModel.objects.aggregate(
             arrayagg=ArrayAgg('integer_field', filter=Q(integer_field__gt=0)),
@@ -220,6 +230,17 @@ class TestGeneralAggregate(PostgreSQLTestCase):
                 )
                 self.assertEqual(values, {'stringagg': expected_output})
 
+    def test_string_agg_jsonfield_ordering(self):
+        values = AggregateTestModel.objects.aggregate(
+            stringagg=StringAgg(
+                KeyTextTransform('lang', 'json_field'),
+                delimiter=';',
+                ordering=KeyTextTransform('lang', 'json_field'),
+                output_field=CharField(),
+            ),
+        )
+        self.assertEqual(values, {'stringagg': 'en;pl'})
+
     def test_string_agg_filter(self):
         values = AggregateTestModel.objects.aggregate(
             stringagg=StringAgg(