pythongh-108494: AC supports pos-only args in limited C API

AC now checks for "#define Py_LIMITED_API" pattern to use the limited
C API.

Lib/test/test_clinic.py

@@ -3542,6 +3542,17 @@ def test_my_int_func(self):
         with self.assertRaises(TypeError):
             _testclinic_limited.my_int_func("xyz")
 
+    def test_my_int_sum(self):
+        with self.assertRaises(TypeError):
+            _testclinic_limited.my_int_sum()
+        with self.assertRaises(TypeError):
+            _testclinic_limited.my_int_sum(1)
+        self.assertEqual(_testclinic_limited.my_int_sum(1, 2), 3)
+        with self.assertRaises(TypeError):
+            _testclinic_limited.my_int_sum(1.0, 2)
+        with self.assertRaises(TypeError):
+            _testclinic_limited.my_int_sum(1, "str")
+
 
 
 class PermutationTests(unittest.TestCase):

Modules/_testclinic_limited.c

@@ -45,9 +45,27 @@ my_int_func_impl(PyObject *module, int arg)
 }
 
 
+/*[clinic input]
+my_int_sum -> int
+
+    x: int
+    y: int
+    /
+
+[clinic start generated code]*/
+
+static int
+my_int_sum_impl(PyObject *module, int x, int y)
+/*[clinic end generated code: output=3e52db9ab5f37e2f input=0edb6796813bf2d3]*/
+{
+    return x + y;
+}
+
+
 static PyMethodDef tester_methods[] = {
     TEST_EMPTY_FUNCTION_METHODDEF
     MY_INT_FUNC_METHODDEF
+    MY_INT_SUM_METHODDEF
     {NULL, NULL}
 };
 

Tools/clinic/clinic.py

@@ -78,6 +78,7 @@
     "noptargs",
     "return_value",
 }
+LIMITED_CAPI_REGEX = re.compile(r'#define +Py_LIMITED_API')
 
 
 class Sentinels(enum.Enum):
@@ -1249,6 +1250,22 @@ def parser_body(
             parser_prototype = self.PARSER_PROTOTYPE_VARARGS
             parser_definition = parser_body(parser_prototype, '    {option_group_parsing}')
 
+        elif not requires_defining_class and pos_only == len(parameters) - pseudo_args and clinic.limited_capi:
+            # positional-only for the limited C API
+            flags = "METH_VARARGS"
+
+            parser_prototype = self.PARSER_PROTOTYPE_VARARGS
+            parser_code = [normalize_snippet("""
+                if (!PyArg_ParseTuple(args, "{format_units}:{name}",
+                    {parse_arguments}))
+                    goto exit;
+            """, indent=4)]
+            argname_fmt = 'args[%d]'
+            declarations = ""
+
+            parser_definition = parser_body(parser_prototype, *parser_code,
+                                            declarations=declarations)
+
         elif not requires_defining_class and pos_only == len(parameters) - pseudo_args:
             if not new_or_init:
                 # positional-only, but no option groups
@@ -2581,10 +2598,6 @@ def parse_file(
 ) -> None:
     verify = not ns.force
     limited_capi = ns.limited_capi
-    # XXX Temporary solution
-    if os.path.basename(filename) == '_testclinic_limited.c':
-        print(f"{filename} uses limited C API")
-        limited_capi = True
     if not output:
         output = filename
 
@@ -2605,6 +2618,9 @@ def parse_file(
     if not find_start_re.search(raw):
         return
 
+    if LIMITED_CAPI_REGEX.search(raw):
+        limited_capi = True
+
     assert isinstance(language, CLanguage)
     clinic = Clinic(language,
                     verify=verify,