Fixed #27654 -- Propagated alters_data attribute to callables overridden in subclasses.

Thanks Shai Berger and Adam Johnson for reviews and the implementation
idea.

tests/template_tests/test_callables.py

@@ -1,5 +1,6 @@
 from unittest import TestCase
 
+from django.db.models.utils import AltersData
 from django.template import Context, Engine
 
 
@@ -63,6 +64,68 @@ class CallableVariablesTests(TestCase):
         # template rendering.
         self.assertEqual(my_doodad.num_calls, 0)
 
+    def test_alters_data_propagation(self):
+        class GrandParentLeft(AltersData):
+            def my_method(self):
+                return 42
+
+            my_method.alters_data = True
+
+        class ParentLeft(GrandParentLeft):
+            def change_alters_data_method(self):
+                return 63
+
+            change_alters_data_method.alters_data = True
+
+            def sub_non_callable_method(self):
+                return 64
+
+            sub_non_callable_method.alters_data = True
+
+        class ParentRight(AltersData):
+            def other_method(self):
+                return 52
+
+            other_method.alters_data = True
+
+        class Child(ParentLeft, ParentRight):
+            def my_method(self):
+                return 101
+
+            def other_method(self):
+                return 102
+
+            def change_alters_data_method(self):
+                return 103
+
+            change_alters_data_method.alters_data = False
+
+            sub_non_callable_method = 104
+
+        class GrandChild(Child):
+            pass
+
+        child = Child()
+        self.assertIs(child.my_method.alters_data, True)
+        self.assertIs(child.other_method.alters_data, True)
+        self.assertIs(child.change_alters_data_method.alters_data, False)
+
+        grand_child = GrandChild()
+        self.assertIs(grand_child.my_method.alters_data, True)
+        self.assertIs(grand_child.other_method.alters_data, True)
+        self.assertIs(grand_child.change_alters_data_method.alters_data, False)
+
+        c = Context({"element": grand_child})
+
+        t = self.engine.from_string("{{ element.my_method }}")
+        self.assertEqual(t.render(c), "")
+        t = self.engine.from_string("{{ element.other_method }}")
+        self.assertEqual(t.render(c), "")
+        t = self.engine.from_string("{{ element.change_alters_data_method }}")
+        self.assertEqual(t.render(c), "103")
+        t = self.engine.from_string("{{ element.sub_non_callable_method }}")
+        self.assertEqual(t.render(c), "104")
+
     def test_do_not_call(self):
         class Doodad:
             do_not_call_in_templates = True