Fixed #30715 -- Fixed crash of ArrayField lookups on ArrayAgg annotations over AutoField.

django/contrib/postgres/fields/array.py

@@ -82,6 +82,10 @@ class ArrayField(CheckFieldDefaultMixin, Field):
         size = self.size or ''
         return '%s[%s]' % (self.base_field.db_type(connection), size)
 
+    def cast_db_type(self, connection):
+        size = self.size or ''
+        return '%s[%s]' % (self.base_field.cast_db_type(connection), size)
+
     def get_placeholder(self, value, compiler, connection):
         return '%s::{}'.format(self.db_type(connection))
 
@@ -193,7 +197,7 @@ class ArrayField(CheckFieldDefaultMixin, Field):
 class ArrayCastRHSMixin:
     def process_rhs(self, compiler, connection):
         rhs, rhs_params = super().process_rhs(compiler, connection)
-        cast_type = self.lhs.output_field.db_type(connection)
+        cast_type = self.lhs.output_field.cast_db_type(connection)
         return '%s::%s' % (rhs, cast_type), rhs_params
 
 

tests/postgres_tests/test_array.py

@@ -25,6 +25,7 @@ from .models import (
 )
 
 try:
+    from django.contrib.postgres.aggregates import ArrayAgg
     from django.contrib.postgres.fields import ArrayField
     from django.contrib.postgres.fields.array import IndexTransform, SliceTransform
     from django.contrib.postgres.forms import (
@@ -280,6 +281,27 @@ class TestQuerying(PostgreSQLTestCase):
             []
         )
 
+    def test_lookups_autofield_array(self):
+        qs = NullableIntegerArrayModel.objects.filter(
+            field__0__isnull=False,
+        ).values('field__0').annotate(
+            arrayagg=ArrayAgg('id'),
+        ).order_by('field__0')
+        tests = (
+            ('contained_by', [self.objs[1].pk, self.objs[2].pk, 0], [2]),
+            ('contains', [self.objs[2].pk], [2]),
+            ('exact', [self.objs[3].pk], [20]),
+            ('overlap', [self.objs[1].pk, self.objs[3].pk], [2, 20]),
+        )
+        for lookup, value, expected in tests:
+            with self.subTest(lookup=lookup):
+                self.assertSequenceEqual(
+                    qs.filter(
+                        **{'arrayagg__' + lookup: value},
+                    ).values_list('field__0', flat=True),
+                    expected,
+                )
+
     def test_index(self):
         self.assertSequenceEqual(
             NullableIntegerArrayModel.objects.filter(field__0=2),