[3.12] gh-107155: Fix help() for lambda function with return annotation (GH-115612)

(cherry picked from commit b9a9e3dd62326b726ad2e8e8efd87ca6327b4019)

1 files changed, 24 insertions, 0 deletions

diff --git a/Lib/test/test_pydoc/test_pydoc.py b/Lib/test/test_pydoc/test_pydoc.py
index b1aa967..a35257c 100644
--- a/Lib/test/test_pydoc/test_pydoc.py
+++ b/Lib/test/test_pydoc/test_pydoc.py
@@ -691,6 +691,30 @@ class PydocDocTest(unittest.TestCase):
         finally:
             pydoc.getpager = getpager_old
 
+    def test_lambda_with_return_annotation(self):
+        func = lambda a, b, c: 1
+        func.__annotations__ = {"return": int}
+        with captured_output('stdout') as help_io:
+            pydoc.help(func)
+        helptext = help_io.getvalue()
+        self.assertIn("lambda (a, b, c) -> int", helptext)
+
+    def test_lambda_without_return_annotation(self):
+        func = lambda a, b, c: 1
+        func.__annotations__ = {"a": int, "b": int, "c": int}
+        with captured_output('stdout') as help_io:
+            pydoc.help(func)
+        helptext = help_io.getvalue()
+        self.assertIn("lambda (a: int, b: int, c: int)", helptext)
+
+    def test_lambda_with_return_and_params_annotation(self):
+        func = lambda a, b, c: 1
+        func.__annotations__ = {"a": int, "b": int, "c": int, "return": int}
+        with captured_output('stdout') as help_io:
+            pydoc.help(func)
+        helptext = help_io.getvalue()
+        self.assertIn("lambda (a: int, b: int, c: int) -> int", helptext)
+
     def test_namedtuple_fields(self):
         Person = namedtuple('Person', ['nickname', 'firstname'])
         with captured_stdout() as help_io: