gh-87106: Fix inspect.signature.bind handling of positional-only arguments with **kwargs

Lib/inspect.py

@@ -3179,6 +3179,8 @@ def _bind(self, args, kwargs, *, partial=False):
  parameters_ex = ()
  arg_vals = iter(args)
 
+ pos_only_param_in_kwargs = []
+
  while True:
  # Let's iterate through the positional arguments and corresponding
  # parameters
@@ -3199,10 +3201,10 @@ def _bind(self, args, kwargs, *, partial=False):
  break
  elif param.name in kwargs:
  if param.kind == _POSITIONAL_ONLY:
-msg = '{arg!r} parameter is positional only, ' \
- 'but was passed as a keyword'
-msg = msg.format(arg=param.name)
-raise TypeError(msg) from None
+# Raise a TypeError once we are sure there is no
+# **kwargs param later.
+pos_only_param_in_kwargs.append(param)
+continue
  parameters_ex = (param,)
  break
  elif (param.kind == _VAR_KEYWORD or
@@ -3284,20 +3286,22 @@ def _bind(self, args, kwargs, *, partial=False):
  format(arg=param_name)) from None
 
  else:
- if param.kind == _POSITIONAL_ONLY:
- # This should never happen in case of a properly built
- # Signature object (but let's have this check here
- # to ensure correct behaviour just in case)
- raise TypeError('{arg!r} parameter is positional only, '
- 'but was passed as a keyword'. \
- format(arg=param.name))
-
  arguments[param_name] = arg_val
 
  if kwargs:
  if kwargs_param is not None:
  # Process our '**kwargs'-like parameter
  arguments[kwargs_param.name] = kwargs
+ elif pos_only_param_in_kwargs:
+ raise TypeError(
+ 'got some positional-only arguments passed as '
+ 'keyword arguments:{arg!r}'.format(
+ arg=', '.join(
+ param.name
+ for param in pos_only_param_in_kwargs
+ ),
+ ),
+ )
  else:
  raise TypeError(
  'got an unexpected keyword argument{arg!r}'.format(

Lib/test/test_inspect/test_inspect.py

@@ -5072,15 +5072,30 @@ def test(a_po, b_po, c_po=3, /, foo=42, *, bar=50, **kwargs):
  self.assertEqual(self.call(test, 1, 2, foo=4, bar=5),
  (1, 2, 3, 4, 5,{}))
 
-with self.assertRaisesRegex(TypeError, "but was passed as a keyword"):
-self.call(test, 1, 2, foo=4, bar=5, c_po=10)
+ self.assertEqual(self.call(test, 1, 2, foo=4, bar=5, c_po=10),
+ (1, 2, 3, 4, 5, {'c_po': 10}))
 
-with self.assertRaisesRegex(TypeError, "parameter is positional only"):
-self.call(test, 1, 2, c_po=4)
+ self.assertEqual(self.call(test, 1, 2, 30, c_po=31, foo=4, bar=5),
+ (1, 2, 30, 4, 5,{'c_po': 31}))
 
- with self.assertRaisesRegex(TypeError, "parameter is positional only"):
+ self.assertEqual(self.call(test, 1, 2, 30, foo=4, bar=5, c_po=31),
+ (1, 2, 30, 4, 5,{'c_po': 31}))
+
+ 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"):
  self.call(test, a_po=1, b_po=2)
 
+ def without_var_kwargs(c_po=3, d_po=4, /):
+ return c_po, d_po
+
+ with self.assertRaisesRegex(
+ TypeError,
+ "positional-only arguments passed as keyword arguments: 'c_po, d_po'",
+ ):
+ self.call(without_var_kwargs, c_po=33, d_po=44)
+
  def test_signature_bind_with_self_arg(self):
  # Issue #17071: one of the parameters is named "self
  def test(a, self, b):

Misc/NEWS.d/next/Library/2023-04-10-00-04-37.gh-issue-87106.UyBnPQ.rst

@@ -0,0 +1,3 @@
+Fixed handling in :meth:`inspect.signature.bind` of keyword arguments having
+the same name as positional-only arguments when a variadic keyword argument
+(e.g. ``**kwargs``) is present.