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

(cherry picked from commit b9a9e3dd62326b726ad2e8e8efd87ca6327b4019)

diff --git a/Lib/pydoc.py b/Lib/pydoc.py
index e770b299360ac6209e495acb73937535cd93cb63..bf855b45134631b382c7af7d47274f57cb22ad20 100755 (executable)
--- a/Lib/pydoc.py
+++ b/Lib/pydoc.py
@@ -1131,7 +1131,8 @@ class HTMLDoc(Doc):
                     # XXX lambda's won't usually have func_annotations['return']
                     # since the syntax doesn't support but it is possible.
                     # So removing parentheses isn't truly safe.
-                    argspec = argspec[1:-1] # remove parentheses
+                    if not object.__annotations__:
+                        argspec = argspec[1:-1] # remove parentheses
         if not argspec:
             argspec = '(...)'
 
@@ -1583,7 +1584,8 @@ location listed above.
                     # XXX lambda's won't usually have func_annotations['return']
                     # since the syntax doesn't support but it is possible.
                     # So removing parentheses isn't truly safe.
-                    argspec = argspec[1:-1] # remove parentheses
+                    if not object.__annotations__:
+                        argspec = argspec[1:-1] # remove parentheses
         if not argspec:
             argspec = '(...)'
         decl = asyncqualifier + title + argspec + note

diff --git a/Lib/test/test_pydoc/test_pydoc.py b/Lib/test/test_pydoc/test_pydoc.py
index b1aa9671a97ee667c9aa9697af87abb4b1219ca8..a35257c8ffc784726da8ffa2d4d3038f5c8c52be 100644 (file)
--- 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:

diff --git a/Misc/NEWS.d/next/Library/2023-08-02-01-17-32.gh-issue-107155.Mj1K9L.rst b/Misc/NEWS.d/next/Library/2023-08-02-01-17-32.gh-issue-107155.Mj1K9L.rst
new file mode 100644 (file)
index 0000000..8362dc0
--- /dev/null
+++ b/Misc/NEWS.d/next/Library/2023-08-02-01-17-32.gh-issue-107155.Mj1K9L.rst
@@ -0,0 +1,3 @@
+Fix incorrect output of ``help(x)`` where ``x`` is a :keyword:`lambda`
+function, which has an ``__annotations__`` dictionary attribute with a
+``"return"`` key.