bpo-30950: Convert round() to Argument Clinic.

Python/bltinmodule.c

@@ -2049,19 +2049,23 @@ builtin_repr(PyObject *module, PyObject *obj)
 }
 
 
-/* AC: cannot convert yet, as needs PEP 457 group support in inspect
- *     or a semantic change to accept None for "ndigits"
- */
+/*[clinic input]
+round as builtin_round
+
+    number: object
+    ndigits: object = NULL
+
+Round a number to a given precision in decimal digits.
+
+The return value is an integer if ndigits is omitted or None.  Otherwise
+the return value has the same type as the number.  ndigits may be negative.
+[clinic start generated code]*/
+
 static PyObject *
-builtin_round(PyObject *self, PyObject *args, PyObject *kwds)
+builtin_round_impl(PyObject *module, PyObject *number, PyObject *ndigits)
+/*[clinic end generated code: output=ff0d9dd176c02ede input=854bc3a217530c3d]*/
 {
-    PyObject *ndigits = NULL;
-    static char *kwlist[] = {"number", "ndigits", 0};
-    PyObject *number, *round, *result;
-
-    if (!PyArg_ParseTupleAndKeywords(args, kwds, "O|O:round",
-                                     kwlist, &number, &ndigits))
-        return NULL;
+    PyObject *round, *result;
 
     if (Py_TYPE(number)->tp_dict == NULL) {
         if (PyType_Ready(Py_TYPE(number)) < 0)
@@ -2085,13 +2089,6 @@ builtin_round(PyObject *self, PyObject *args, PyObject *kwds)
     return result;
 }
 
-PyDoc_STRVAR(round_doc,
-"round(number[, ndigits]) -> number\n\
-\n\
-Round a number to a given precision in decimal digits (default 0 digits).\n\
-This returns an int when called with one argument, otherwise the\n\
-same type as the number. ndigits may be negative.");
-
 
 /*AC: we need to keep the kwds dict intact to easily call into the
  * list.sort method, which isn't currently supported in AC. So we just use
@@ -2648,7 +2645,7 @@ static PyMethodDef builtin_methods[] = {
     BUILTIN_POW_METHODDEF
     {"print",           (PyCFunction)builtin_print,      METH_FASTCALL | METH_KEYWORDS, print_doc},
     BUILTIN_REPR_METHODDEF
-    {"round",           (PyCFunction)builtin_round,      METH_VARARGS | METH_KEYWORDS, round_doc},
+    BUILTIN_ROUND_METHODDEF
     BUILTIN_SETATTR_METHODDEF
     BUILTIN_SORTED_METHODDEF
     BUILTIN_SUM_METHODDEF

Python/clinic/bltinmodule.c.h

@@ -573,6 +573,40 @@ PyDoc_STRVAR(builtin_repr__doc__,
 #define BUILTIN_REPR_METHODDEF    \
     {"repr", (PyCFunction)builtin_repr, METH_O, builtin_repr__doc__},
 
+PyDoc_STRVAR(builtin_round__doc__,
+"round($module, /, number, ndigits=None)\n"
+"--\n"
+"\n"
+"Round a number to a given precision in decimal digits.\n"
+"\n"
+"The return value is an integer if ndigits is omitted or None.  Otherwise\n"
+"the return value has the same type as the number.  ndigits may be negative.");
+
+#define BUILTIN_ROUND_METHODDEF    \
+    {"round", (PyCFunction)builtin_round, METH_FASTCALL|METH_KEYWORDS, builtin_round__doc__},
+
+static PyObject *
+builtin_round_impl(PyObject *module, PyObject *number, PyObject *ndigits);
+
+static PyObject *
+builtin_round(PyObject *module, PyObject **args, Py_ssize_t nargs, PyObject *kwnames)
+{
+    PyObject *return_value = NULL;
+    static const char * const _keywords[] = {"number", "ndigits", NULL};
+    static _PyArg_Parser _parser = {"O|O:round", _keywords, 0};
+    PyObject *number;
+    PyObject *ndigits = NULL;
+
+    if (!_PyArg_ParseStackAndKeywords(args, nargs, kwnames, &_parser,
+        &number, &ndigits)) {
+        goto exit;
+    }
+    return_value = builtin_round_impl(module, number, ndigits);
+
+exit:
+    return return_value;
+}
+
 PyDoc_STRVAR(builtin_sum__doc__,
 "sum($module, iterable, start=0, /)\n"
 "--\n"
@@ -676,4 +710,4 @@ builtin_issubclass(PyObject *module, PyObject **args, Py_ssize_t nargs)
 exit:
     return return_value;
 }
-/*[clinic end generated code: output=09752daa8cdd6ec7 input=a9049054013a1b77]*/
+/*[clinic end generated code: output=d46a224ac804eef1 input=a9049054013a1b77]*/