[2.0.x] Refs #23260 -- Tested nested generator input to unordered_list template filter.

Backport of b21b1b10af from master

tests/template_tests/filter_tests/test_unordered_list.py

@@ -110,6 +110,20 @@ class FunctionTests(SimpleTestCase):
             '\t<li>ulitem-a</li>\n\t<li>ulitem-b</li>\n\t<li>ulitem-&lt;a&gt;c&lt;/a&gt;</li>',
         )
 
+    def test_nested_generators(self):
+        def inner_generator():
+            yield from ('B', 'C')
+
+        def item_generator():
+            yield 'A'
+            yield inner_generator()
+            yield 'D'
+
+        self.assertEqual(
+            unordered_list(item_generator()),
+            '\t<li>A\n\t<ul>\n\t\t<li>B</li>\n\t\t<li>C</li>\n\t</ul>\n\t</li>\n\t<li>D</li>',
+        )
+
     def test_ulitem_autoescape_off(self):
         class ULItem:
             def __init__(self, title):