gh-118814: Fix the TypeVar constructor when name is passed by keyword (GH-122664)

Fix _PyArg_UnpackKeywordsWithVararg for the case when argument for
positional-or-keyword parameter is passed by keyword.
There was only one such case in the stdlib -- the TypeVar constructor.

Lib/test/test_clinic.py

@@ -3334,11 +3334,27 @@ class ClinicFunctionalTest(unittest.TestCase):
         self.assertEqual(ac_tester.vararg(1, 2, 3, 4), (1, (2, 3, 4)))
 
     def test_vararg_with_default(self):
-        with self.assertRaises(TypeError):
-            ac_tester.vararg_with_default()
-        self.assertEqual(ac_tester.vararg_with_default(1, b=False), (1, (), False))
-        self.assertEqual(ac_tester.vararg_with_default(1, 2, 3, 4), (1, (2, 3, 4), False))
-        self.assertEqual(ac_tester.vararg_with_default(1, 2, 3, 4, b=True), (1, (2, 3, 4), True))
+        fn = ac_tester.vararg_with_default
+        self.assertRaises(TypeError, fn)
+        self.assertRaises(TypeError, fn, 1, a=2)
+        self.assertEqual(fn(1, b=2), (1, (), True))
+        self.assertEqual(fn(1, 2, 3, 4), (1, (2, 3, 4), False))
+        self.assertEqual(fn(1, 2, 3, 4, b=5), (1, (2, 3, 4), True))
+        self.assertEqual(fn(a=1), (1, (), False))
+        self.assertEqual(fn(a=1, b=2), (1, (), True))
+
+    def test_vararg_with_default2(self):
+        fn = ac_tester.vararg_with_default2
+        self.assertRaises(TypeError, fn)
+        self.assertRaises(TypeError, fn, 1, a=2)
+        self.assertEqual(fn(1, b=2), (1, (), 2, None))
+        self.assertEqual(fn(1, b=2, c=3), (1, (), 2, 3))
+        self.assertEqual(fn(1, 2, 3), (1, (2, 3), None, None))
+        self.assertEqual(fn(1, 2, 3, b=4), (1, (2, 3), 4, None))
+        self.assertEqual(fn(1, 2, 3, b=4, c=5), (1, (2, 3), 4, 5))
+        self.assertEqual(fn(a=1), (1, (), None, None))
+        self.assertEqual(fn(a=1, b=2), (1, (), 2, None))
+        self.assertEqual(fn(a=1, b=2, c=3), (1, (), 2, 3))
 
     def test_vararg_with_only_defaults(self):
         self.assertEqual(ac_tester.vararg_with_only_defaults(), ((), None))

Lib/test/test_typing.py

@@ -579,6 +579,55 @@ class TypeVarTests(BaseTestCase):
         self.assertEqual(T.__name__, "T")
         self.assertEqual(T.__constraints__, ())
         self.assertIs(T.__bound__, None)
+        self.assertIs(T.__default__, typing.NoDefault)
+        self.assertIs(T.__covariant__, False)
+        self.assertIs(T.__contravariant__, False)
+        self.assertIs(T.__infer_variance__, False)
+
+        T = TypeVar(name="T", bound=type)
+        self.assertEqual(T.__name__, "T")
+        self.assertEqual(T.__constraints__, ())
+        self.assertIs(T.__bound__, type)
+        self.assertIs(T.__default__, typing.NoDefault)
+        self.assertIs(T.__covariant__, False)
+        self.assertIs(T.__contravariant__, False)
+        self.assertIs(T.__infer_variance__, False)
+
+        T = TypeVar(name="T", default=())
+        self.assertEqual(T.__name__, "T")
+        self.assertEqual(T.__constraints__, ())
+        self.assertIs(T.__bound__, None)
+        self.assertIs(T.__default__, ())
+        self.assertIs(T.__covariant__, False)
+        self.assertIs(T.__contravariant__, False)
+        self.assertIs(T.__infer_variance__, False)
+
+        T = TypeVar(name="T", covariant=True)
+        self.assertEqual(T.__name__, "T")
+        self.assertEqual(T.__constraints__, ())
+        self.assertIs(T.__bound__, None)
+        self.assertIs(T.__default__, typing.NoDefault)
+        self.assertIs(T.__covariant__, True)
+        self.assertIs(T.__contravariant__, False)
+        self.assertIs(T.__infer_variance__, False)
+
+        T = TypeVar(name="T", contravariant=True)
+        self.assertEqual(T.__name__, "T")
+        self.assertEqual(T.__constraints__, ())
+        self.assertIs(T.__bound__, None)
+        self.assertIs(T.__default__, typing.NoDefault)
+        self.assertIs(T.__covariant__, False)
+        self.assertIs(T.__contravariant__, True)
+        self.assertIs(T.__infer_variance__, False)
+
+        T = TypeVar(name="T", infer_variance=True)
+        self.assertEqual(T.__name__, "T")
+        self.assertEqual(T.__constraints__, ())
+        self.assertIs(T.__bound__, None)
+        self.assertIs(T.__default__, typing.NoDefault)
+        self.assertIs(T.__covariant__, False)
+        self.assertIs(T.__contravariant__, False)
+        self.assertIs(T.__infer_variance__, True)
 
 
 class TypeParameterDefaultsTests(BaseTestCase):

Misc/NEWS.d/next/Library/2024-08-04-14-07-18.gh-issue-118814.uiyks1.rst

@@ -0,0 +1 @@
+Fix the :class:`typing.TypeVar` constructor when name is passed by keyword.

Modules/_testclinic.c

@@ -1033,6 +1033,25 @@ vararg_with_default_impl(PyObject *module, PyObject *a, PyObject *args,
 }
 
 
+/*[clinic input]
+vararg_with_default2
+
+    a: object
+    *args: object
+    b: object = None
+    c: object = None
+
+[clinic start generated code]*/
+
+static PyObject *
+vararg_with_default2_impl(PyObject *module, PyObject *a, PyObject *args,
+                          PyObject *b, PyObject *c)
+/*[clinic end generated code: output=a0fb7c37796e2129 input=59fb22f5f0a8925f]*/
+{
+    return pack_arguments_newref(4, a, args, b, c);
+}
+
+
 /*[clinic input]
 vararg_with_only_defaults
 
@@ -1907,6 +1926,7 @@ static PyMethodDef tester_methods[] = {
     VARARG_AND_POSONLY_METHODDEF
     VARARG_METHODDEF
     VARARG_WITH_DEFAULT_METHODDEF
+    VARARG_WITH_DEFAULT2_METHODDEF
     VARARG_WITH_ONLY_DEFAULTS_METHODDEF
     GH_32092_OOB_METHODDEF
     GH_32092_KW_PASS_METHODDEF

Modules/clinic/_testclinic.c.h

@@ -2742,6 +2742,78 @@ exit:
     return return_value;
 }
 
+PyDoc_STRVAR(vararg_with_default2__doc__,
+"vararg_with_default2($module, /, a, *args, b=None, c=None)\n"
+"--\n"
+"\n");
+
+#define VARARG_WITH_DEFAULT2_METHODDEF    \
+    {"vararg_with_default2", _PyCFunction_CAST(vararg_with_default2), METH_FASTCALL|METH_KEYWORDS, vararg_with_default2__doc__},
+
+static PyObject *
+vararg_with_default2_impl(PyObject *module, PyObject *a, PyObject *args,
+                          PyObject *b, PyObject *c);
+
+static PyObject *
+vararg_with_default2(PyObject *module, PyObject *const *args, Py_ssize_t nargs, PyObject *kwnames)
+{
+    PyObject *return_value = NULL;
+    #if defined(Py_BUILD_CORE) && !defined(Py_BUILD_CORE_MODULE)
+
+    #define NUM_KEYWORDS 3
+    static struct {
+        PyGC_Head _this_is_not_used;
+        PyObject_VAR_HEAD
+        PyObject *ob_item[NUM_KEYWORDS];
+    } _kwtuple = {
+        .ob_base = PyVarObject_HEAD_INIT(&PyTuple_Type, NUM_KEYWORDS)
+        .ob_item = { _Py_LATIN1_CHR('a'), _Py_LATIN1_CHR('b'), _Py_LATIN1_CHR('c'), },
+    };
+    #undef NUM_KEYWORDS
+    #define KWTUPLE (&_kwtuple.ob_base.ob_base)
+
+    #else  // !Py_BUILD_CORE
+    #  define KWTUPLE NULL
+    #endif  // !Py_BUILD_CORE
+
+    static const char * const _keywords[] = {"a", "b", "c", NULL};
+    static _PyArg_Parser _parser = {
+        .keywords = _keywords,
+        .fname = "vararg_with_default2",
+        .kwtuple = KWTUPLE,
+    };
+    #undef KWTUPLE
+    PyObject *argsbuf[4];
+    Py_ssize_t noptargs = Py_MIN(nargs, 1) + (kwnames ? PyTuple_GET_SIZE(kwnames) : 0) - 1;
+    PyObject *a;
+    PyObject *__clinic_args = NULL;
+    PyObject *b = Py_None;
+    PyObject *c = Py_None;
+
+    args = _PyArg_UnpackKeywordsWithVararg(args, nargs, NULL, kwnames, &_parser, 1, 1, 0, 1, argsbuf);
+    if (!args) {
+        goto exit;
+    }
+    a = args[0];
+    __clinic_args = args[1];
+    if (!noptargs) {
+        goto skip_optional_kwonly;
+    }
+    if (args[2]) {
+        b = args[2];
+        if (!--noptargs) {
+            goto skip_optional_kwonly;
+        }
+    }
+    c = args[3];
+skip_optional_kwonly:
+    return_value = vararg_with_default2_impl(module, a, __clinic_args, b, c);
+
+exit:
+    Py_XDECREF(__clinic_args);
+    return return_value;
+}
+
 PyDoc_STRVAR(vararg_with_only_defaults__doc__,
 "vararg_with_only_defaults($module, /, *args, b=None)\n"
 "--\n"
@@ -3418,4 +3490,4 @@ _testclinic_TestClass_get_defining_class_arg(PyObject *self, PyTypeObject *cls,
 exit:
     return return_value;
 }
-/*[clinic end generated code: output=0d0ceed6c46547bb input=a9049054013a1b77]*/
+/*[clinic end generated code: output=cf3b04bd2ecf6e26 input=a9049054013a1b77]*/

Python/getargs.c

@@ -2601,7 +2601,7 @@ _PyArg_UnpackKeywordsWithVararg(PyObject *const *args, Py_ssize_t nargs,
          *
          * Otherwise, we leave a place at `buf[vararg]` for vararg tuple
          * so the index is `i + 1`. */
-        if (nargs < vararg && i != vararg) {
+        if (i < vararg) {
             buf[i] = current_arg;
         }
         else {