gh-127610: Added validation for more than one var-positional and var-keyword parameters in inspect.Signature (GH-127657)

2 files changed, 19 insertions, 0 deletions

diff --git a/Lib/inspect.py b/Lib/inspect.py
index e3f74e9f..b7d8271 100644
--- a/Lib/inspect.py
+++ b/Lib/inspect.py
@@ -2943,11 +2943,19 @@ class Signature:
                 params = OrderedDict()
                 top_kind = _POSITIONAL_ONLY
                 seen_default = False
+                seen_var_parameters = set()
 
                 for param in parameters:
                     kind = param.kind
                     name = param.name
 
+                    if kind in (_VAR_POSITIONAL, _VAR_KEYWORD):
+                        if kind in seen_var_parameters:
+                            msg = f'more than one {kind.description} parameter'
+                            raise ValueError(msg)
+
+                        seen_var_parameters.add(kind)
+
                     if kind < top_kind:
                         msg = (
                             'wrong parameter order: {} parameter before {} '
diff --git a/Lib/test/test_inspect/test_inspect.py b/Lib/test/test_inspect/test_inspect.py
index a92627a..1ecf18b 100644
--- a/Lib/test/test_inspect/test_inspect.py
+++ b/Lib/test/test_inspect/test_inspect.py
@@ -2992,6 +2992,17 @@ class TestSignatureObject(unittest.TestCase):
         with self.assertRaisesRegex(ValueError, 'follows default argument'):
             S((pkd, pk))
 
+        second_args = args.replace(name="second_args")
+        with self.assertRaisesRegex(ValueError, 'more than one variadic positional parameter'):
+            S((args, second_args))
+
+        with self.assertRaisesRegex(ValueError, 'more than one variadic positional parameter'):
+            S((args, ko, second_args))
+
+        second_kwargs = kwargs.replace(name="second_kwargs")
+        with self.assertRaisesRegex(ValueError, 'more than one variadic keyword parameter'):
+            S((kwargs, second_kwargs))
+
     def test_signature_object_pickle(self):
         def foo(a, b, *, c:1={}, **kw) -> {42:'ham'}: pass
         foo_partial = functools.partial(foo, a=1)