gh-90795: Fix error message incorrectly including "positional"

Lib/inspect.py

@@ -1381,7 +1381,7 @@ def convert(name, locals=locals,
         specs.append(formatvarkw(varkw) + formatvalue(locals[varkw]))
     return '(' + ', '.join(specs) + ')'
 
-def _missing_arguments(f_name, argnames, pos, values):
+def _missing_arguments(f_name, argnames, pos, values, *, has_posonly=False):
     names = [repr(name) for name in argnames if name not in values]
     missing = len(names)
     if missing == 1:
@@ -1392,10 +1392,18 @@ def _missing_arguments(f_name, argnames, pos, values):
         tail = ", {} and {}".format(*names[-2:])
         del names[-2:]
         s = ", ".join(names) + tail
-    raise TypeError("%s() missing %i required %s argument%s: %s" %
-                    (f_name, missing,
-                      "positional" if pos else "keyword-only",
-                      "" if missing == 1 else "s", s))
+
+    if pos:
+        qualifier = "positional" if has_posonly else ""
+    else:
+        qualifier = "keyword-only"
+    if qualifier:
+        raise TypeError("%s() missing %i required %s argument%s: %s" %
+                        (f_name, missing, qualifier,
+                         "" if missing == 1 else "s", s))
+    else:
+        raise TypeError("%s() missing %i required argument%s: %s" %
+                        (f_name, missing, "" if missing == 1 else "s", s))
 
 def _too_many(f_name, args, kwonly, varargs, defcount, given, values):
     atleast = len(args) - defcount
@@ -1429,7 +1437,9 @@ def getcallargs(func, /, *positional, **named):
     f_name = func.__name__
     arg2value = {}
 
-
+    num_posonly = 0
+    if hasattr(func, '__code__'):
+        num_posonly = func.__code__.co_posonlyargcount
     if ismethod(func) and func.__self__ is not None:
         # implicit 'self' (or 'cls' for classmethods) argument
         positional = (func.__self__,) + positional
@@ -1463,7 +1473,9 @@ def getcallargs(func, /, *positional, **named):
         req = args[:num_args - num_defaults]
         for arg in req:
             if arg not in arg2value:
-                _missing_arguments(f_name, req, True, arg2value)
+                missing_posonly = any(i < num_posonly for i, name in enumerate(args)
+                                    if name in req and name not in arg2value)
+                _missing_arguments(f_name, req, True, arg2value, has_posonly=missing_posonly)
         for i, arg in enumerate(args[num_args - num_defaults:]):
             if arg not in arg2value:
                 arg2value[arg] = defaults[i]
@@ -1475,7 +1487,7 @@ def getcallargs(func, /, *positional, **named):
             else:
                 missing += 1
     if missing:
-        _missing_arguments(f_name, kwonlyargs, False, arg2value)
+        _missing_arguments(f_name, kwonlyargs, False, arg2value, has_posonly=False)
     return arg2value
 
 ClosureVars = namedtuple('ClosureVars', 'nonlocals globals builtins unbound')

Lib/test/test_call.py

@@ -920,7 +920,7 @@ def check_raises_type_error(self, message):
         self.assertEqual(str(cm.exception), message)
 
     def test_missing_arguments(self):
-        msg = "A.method_two_args() missing 1 required positional argument: 'y'"
+        msg = "A.method_two_args() missing 1 required argument: 'y'"
         with self.check_raises_type_error(msg):
             A().method_two_args("x")
 

Lib/test/test_dataclasses/__init__.py

@@ -534,7 +534,7 @@ class C:
 
         with self.assertRaisesRegex(TypeError,
                                     r"__init__\(\) missing 1 required "
-                                    "positional argument: 'x'"):
+                                    "argument: 'x'"):
             C()
 
     def test_field_default(self):
@@ -935,7 +935,7 @@ class C:
             x: int=field(default=MISSING)
         with self.assertRaisesRegex(TypeError,
                                     r'__init__\(\) missing 1 required '
-                                    'positional argument'):
+                                    'argument'):
             C()
         self.assertNotIn('x', C.__dict__)
 
@@ -944,7 +944,7 @@ class D:
             x: int
         with self.assertRaisesRegex(TypeError,
                                     r'__init__\(\) missing 1 required '
-                                    'positional argument'):
+                                    'argument'):
             D()
         self.assertNotIn('x', D.__dict__)
 
@@ -957,7 +957,7 @@ class C:
             x: int=field(default_factory=MISSING)
         with self.assertRaisesRegex(TypeError,
                                     r'__init__\(\) missing 1 required '
-                                    'positional argument'):
+                                    'argument'):
             C()
         self.assertNotIn('x', C.__dict__)
 
@@ -966,7 +966,7 @@ class D:
             x: int=field(default=MISSING, default_factory=MISSING)
         with self.assertRaisesRegex(TypeError,
                                     r'__init__\(\) missing 1 required '
-                                    'positional argument'):
+                                    'argument'):
             D()
         self.assertNotIn('x', D.__dict__)
 
@@ -3260,7 +3260,7 @@ class C:
         #  also have a default value (of type
         #  types.MemberDescriptorType).
         with self.assertRaisesRegex(TypeError,
-                                    r"__init__\(\) missing 1 required positional argument: 'x'"):
+                                    r"__init__\(\) missing 1 required argument: 'x'"):
             C()
 
         # We can create an instance, and assign to x.
@@ -3784,7 +3784,7 @@ def __init_subclass__(cls, arg):
 
         with self.assertRaisesRegex(
             TypeError,
-            "missing 1 required positional argument: 'arg'",
+            "missing 1 required argument: 'arg'",
         ):
             @dataclass(slots=True)
             class WithWrongSuper(WrongSuper, arg=1):
@@ -4018,7 +4018,7 @@ def __set__(self, instance: Any, value: int) -> None:
         class C:
             i: D = D()
 
-        with self.assertRaisesRegex(TypeError, 'missing 1 required positional argument'):
+        with self.assertRaisesRegex(TypeError, 'missing 1 required argument'):
             c = C()
 
 class TestStringAnnotations(unittest.TestCase):
@@ -4227,7 +4227,7 @@ class Base2:
         C = make_dataclass('C',
                            [('y', int)],
                            bases=(Base1, Base2))
-        with self.assertRaisesRegex(TypeError, 'required positional'):
+        with self.assertRaisesRegex(TypeError, 'required argument'):
             c = C(2)
         c = C(1, 2)
         self.assertIsInstance(c, C)

Lib/test/test_extcall.py

@@ -111,17 +111,17 @@
     >>> g()
     Traceback (most recent call last):
       ...
-    TypeError: g() missing 1 required positional argument: 'x'
+    TypeError: g() missing 1 required argument: 'x'
 
     >>> g(*())
     Traceback (most recent call last):
       ...
-    TypeError: g() missing 1 required positional argument: 'x'
+    TypeError: g() missing 1 required argument: 'x'
 
     >>> g(*(), **{})
     Traceback (most recent call last):
       ...
-    TypeError: g() missing 1 required positional argument: 'x'
+    TypeError: g() missing 1 required argument: 'x'
 
     >>> g(1)
     1 () {}
@@ -505,27 +505,27 @@
     >>> f()
     Traceback (most recent call last):
       ...
-    TypeError: f() missing 1 required positional argument: 'a'
+    TypeError: f() missing 1 required argument: 'a'
     >>> def f(a, b): pass
     >>> f()
     Traceback (most recent call last):
       ...
-    TypeError: f() missing 2 required positional arguments: 'a' and 'b'
+    TypeError: f() missing 2 required arguments: 'a' and 'b'
     >>> def f(a, b, c): pass
     >>> f()
     Traceback (most recent call last):
       ...
-    TypeError: f() missing 3 required positional arguments: 'a', 'b', and 'c'
+    TypeError: f() missing 3 required arguments: 'a', 'b', and 'c'
     >>> def f(a, b, c, d, e): pass
     >>> f()
     Traceback (most recent call last):
       ...
-    TypeError: f() missing 5 required positional arguments: 'a', 'b', 'c', 'd', and 'e'
+    TypeError: f() missing 5 required arguments: 'a', 'b', 'c', 'd', and 'e'
     >>> def f(a, b=4, c=5, d=5): pass
     >>> f(c=12, b=9)
     Traceback (most recent call last):
       ...
-    TypeError: f() missing 1 required positional argument: 'a'
+    TypeError: f() missing 1 required argument: 'a'
 
 Same with keyword only args:
 

Lib/test/test_positional_only_arg.py

@@ -142,7 +142,7 @@ def f(a, b, /):
     def test_positional_only_and_arg_invalid_calls(self):
         def f(a, b, /, c):
             pass
-        with self.assertRaisesRegex(TypeError, r"f\(\) missing 1 required positional argument: 'c'"):
+        with self.assertRaisesRegex(TypeError, r"f\(\) missing 1 required argument: 'c'"):
             f(1, 2)
         with self.assertRaisesRegex(TypeError, r"f\(\) missing 2 required positional arguments: 'b' and 'c'"):
             f(1)
@@ -170,7 +170,7 @@ def f(a, b, /, c, *, d, e):
             f(1, 2, 3, e=2)
         with self.assertRaisesRegex(TypeError, r"missing 2 required keyword-only arguments: 'd' and 'e'"):
             f(1, 2, 3)
-        with self.assertRaisesRegex(TypeError, r"f\(\) missing 1 required positional argument: 'c'"):
+        with self.assertRaisesRegex(TypeError, r"f\(\) missing 1 required argument: 'c'"):
             f(1, 2)
         with self.assertRaisesRegex(TypeError, r"f\(\) missing 2 required positional arguments: 'b' and 'c'"):
             f(1)
@@ -278,7 +278,7 @@ def g(x2,/,y2):
             return g
 
         self.assertEqual(f(1,2)(3,4), 10)
-        with self.assertRaisesRegex(TypeError, r"g\(\) missing 1 required positional argument: 'y2'"):
+        with self.assertRaisesRegex(TypeError, r"g\(\) missing 1 required argument: 'y2'"):
             f(1,2)(3)
         with self.assertRaisesRegex(TypeError, r"g\(\) takes 2 positional arguments but 3 were given"):
             f(1,2)(3,4,5)
@@ -296,7 +296,7 @@ def g(x2,/,y2):
             return g
 
         self.assertEqual(f(1,2)(3,4), 10)
-        with self.assertRaisesRegex(TypeError, r"g\(\) missing 1 required positional argument: 'y2'"):
+        with self.assertRaisesRegex(TypeError, r"g\(\) missing 1 required argument: 'y2'"):
             f(1,2)(3)
         with self.assertRaisesRegex(TypeError, r"g\(\) takes 2 positional arguments but 3 were given"):
             f(1,2)(3,4,5)

Misc/NEWS.d/next/Core_and_Builtins/2025-10-06-21-33-55.gh-issue-90795.Oz7t1l.rst

@@ -0,0 +1,2 @@
+Fix an error message that incorrectly specified a missing argument as
+"positional" in function calls.

Python/ceval.c

@@ -1322,13 +1322,22 @@ format_missing(PyThreadState *tstate, const char *kind,
     }
     if (name_str == NULL)
         return;
-    _PyErr_Format(tstate, PyExc_TypeError,
-                  "%U() missing %i required %s argument%s: %U",
-                  qualname,
-                  len,
-                  kind,
-                  len == 1 ? "" : "s",
-                  name_str);
+    if (kind[0] == '\0') {
+        _PyErr_Format(tstate, PyExc_TypeError,
+                      "%U() missing %i required argument%s: %U",
+                      qualname,
+                      len,
+                      len == 1 ? "" : "s",
+                      name_str);
+    } else {
+        _PyErr_Format(tstate, PyExc_TypeError,
+                      "%U() missing %i required %s argument%s: %U",
+                      qualname,
+                      len,
+                      kind,
+                      len == 1 ? "" : "s",
+                      name_str);
+    }
     Py_DECREF(name_str);
 }
 
@@ -1340,9 +1349,33 @@ missing_arguments(PyThreadState *tstate, PyCodeObject *co,
     Py_ssize_t i, j = 0;
     Py_ssize_t start, end;
     int positional = (defcount != -1);
-    const char *kind = positional ? "positional" : "keyword-only";
+    const char *kind = "";
     PyObject *missing_names;
 
+    if (positional) {
+        int has_posonly_missing = 0;
+
+        start = 0;
+        end = co->co_argcount - defcount;
+
+        for (i = start; i < end; i++) {
+            if (PyStackRef_IsNull(localsplus[i])) {
+                if (i < co->co_posonlyargcount) {
+                    has_posonly_missing = 1;
+                    break;
+                }
+            }
+        }
+
+        if (has_posonly_missing) {
+            kind = "positional";
+        } else {
+            kind = "";
+        }
+    } else {
+        kind = "keyword-only";
+    }
+
     /* Compute the names of the arguments that are missing. */
     missing_names = PyList_New(missing);
     if (missing_names == NULL)