gh-155258: Make the curses.complexstr signature introspectable

Author: fedonman

Lib/test/test_curses.py

@@ -696,6 +696,10 @@ def test_complexstr(self):
                           lambda: curses.complexstr([cc('A')], attr=B))
         self.assertRaises(TypeError,
                           lambda: curses.complexstr(['A'], pair=0))
+        # The signature is introspectable: attr and pair have a default that
+        # can be rendered.
+        self.assertEqual(str(inspect.signature(curses.complexstr)),
+                         '(cells, /, attr=None, pair=None)')
 
     def test_in_wchstr(self):
         # in_wchstr() returns a complexstr -- the styled-cell counterpart of

Modules/_cursesmodule.c

@@ -1412,9 +1412,9 @@ _curses.complexstr.__new__ as complexstr_new
     cells: object
         An iterable of cells, each a complexchar or a str.
     /
-    attr: object = NULL
+    attr: object(c_default="NULL") = None
         Attributes applied to every cell (only with a string).
-    pair: object = NULL
+    pair: object(c_default="NULL") = None
         Color pair applied to every cell (only with a string).
 
 An immutable string of styled wide-character cells.
@@ -1431,7 +1431,7 @@ rendition, and attr and pair must be omitted.
 static PyObject *
 complexstr_new_impl(PyTypeObject *type, PyObject *cells, PyObject *attr,
                     PyObject *pair)
-/*[clinic end generated code: output=ef8a53143d35a32a input=9b75aee973cc6565]*/
+/*[clinic end generated code: output=ef8a53143d35a32a input=f152717ac17b5b88]*/
 {
     cursesmodule_state *state = get_cursesmodule_state_by_cls(type);
     /* A string is split into cells (grouping combining characters), not