[Python-checkins] [3.12] gh-130164: Fix inspect.Signature.bind() handling of positional-only args without defaults (GH-130192) (GH-132259)

[serhiy-storchaka]

https://github.com/python/cpython/commit/40f81e1060aa9c8034b568e8003cd6a0d32ff285
commit: 40f81e1060aa9c8034b568e8003cd6a0d32ff285
branch: 3.12
author: Miss Islington (bot) <31488909+miss-isling...@users.noreply.github.com>
committer: serhiy-storchaka <storch...@gmail.com>
date: 2025-04-08T09:39:45Z
summary:

[3.12] gh-130164: Fix inspect.Signature.bind() handling of positional-only args 
without defaults (GH-130192) (GH-132259)

Follow-up to 9c15202.
(cherry picked from commit dab456dcefd886bde44eb204dc6f1b2f14de0e9d)

Co-authored-by: Jacob Walls <jacobtylerwa...@gmail.com>

files:
A Misc/NEWS.d/next/Library/2025-02-16-08-56-48.gh-issue-130164.vvoaU2.rst
M Lib/inspect.py
M Lib/test/test_inspect/test_inspect.py

diff --git a/Lib/inspect.py b/Lib/inspect.py
index b630cb2835957b..2a8d9b053cc5d1 100644
--- a/Lib/inspect.py
+++ b/Lib/inspect.py
@@ -3161,6 +3161,9 @@ def _bind(self, args, kwargs, *, partial=False):
                         break
                     elif param.name in kwargs:
                         if param.kind == _POSITIONAL_ONLY:
+                            if param.default is _empty:
+                                msg = f'missing a required positional-only 
argument: {param.name!r}'
+                                raise TypeError(msg)
                             # Raise a TypeError once we are sure there is no
                             # **kwargs param later.
                             pos_only_param_in_kwargs.append(param)
diff --git a/Lib/test/test_inspect/test_inspect.py 
b/Lib/test/test_inspect/test_inspect.py
index eae8e46b9cb9b2..792a8fa90f593c 100644
--- a/Lib/test/test_inspect/test_inspect.py
+++ b/Lib/test/test_inspect/test_inspect.py
@@ -4701,7 +4701,11 @@ class TestSignatureBind(unittest.TestCase):
     def call(func, *args, **kwargs):
         sig = inspect.signature(func)
         ba = sig.bind(*args, **kwargs)
-        return func(*ba.args, **ba.kwargs)
+        # Prevent unexpected success of assertRaises(TypeError, ...)
+        try:
+            return func(*ba.args, **ba.kwargs)
+        except TypeError as e:
+            raise AssertionError from e
 
     def test_signature_bind_empty(self):
         def test():
@@ -4901,7 +4905,7 @@ def test(a_po, b_po, c_po=3, /, foo=42, *, bar=50, 
**kwargs):
         self.assertEqual(self.call(test, 1, 2, c_po=4),
                          (1, 2, 3, 42, 50, {'c_po': 4}))
 
-        with self.assertRaisesRegex(TypeError, "missing 2 required positional 
arguments"):
+        with self.assertRaisesRegex(TypeError, "missing a required 
positional-only argument: 'a_po'"):
             self.call(test, a_po=1, b_po=2)
 
         def without_var_kwargs(c_po=3, d_po=4, /):
diff --git 
a/Misc/NEWS.d/next/Library/2025-02-16-08-56-48.gh-issue-130164.vvoaU2.rst 
b/Misc/NEWS.d/next/Library/2025-02-16-08-56-48.gh-issue-130164.vvoaU2.rst
new file mode 100644
index 00000000000000..a4a47cb02dfcad
--- /dev/null
+++ b/Misc/NEWS.d/next/Library/2025-02-16-08-56-48.gh-issue-130164.vvoaU2.rst
@@ -0,0 +1,3 @@
+Fixed failure to raise :exc:`TypeError` in :meth:`inspect.Signature.bind`
+for positional-only arguments provided by keyword when a variadic keyword
+argument (e.g. ``**kwargs``) is present.

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