bpo-37206: Unrepresentable default values no longer represented as None. (GH-13933)

In ArgumentClinic, value "NULL" should now be used only for unrepresentable default values
(like in the optional third parameter of getattr). "None" should be used if None is accepted
as argument and passing None has the same effect as not passing the argument at all.

1 files changed, 6 insertions, 7 deletions

diff --git a/Tools/clinic/clinic.py b/Tools/clinic/clinic.py
index cec7c5392d..c5edc7c933 100755
--- a/Tools/clinic/clinic.py
+++ b/Tools/clinic/clinic.py
@@ -43,9 +43,6 @@ NoneType = type(None)
 
 version = '1'
 
-_empty = inspect._empty
-_void = inspect._void
-
 NoneType = type(None)
 
 class Unspecified:
@@ -2175,7 +2172,7 @@ class Function:
     def __init__(self, parameters=None, *, name,
                  module, cls=None, c_basename=None,
                  full_name=None,
-                 return_converter, return_annotation=_empty,
+                 return_converter, return_annotation=inspect.Signature.empty,
                  docstring=None, kind=CALLABLE, coexist=False,
                  docstring_only=False):
         self.parameters = parameters or collections.OrderedDict()
@@ -2253,8 +2250,8 @@ class Parameter:
     Mutable duck type of inspect.Parameter.
     """
 
-    def __init__(self, name, kind, *, default=_empty,
-                 function, converter, annotation=_empty,
+    def __init__(self, name, kind, *, default=inspect.Parameter.empty,
+                 function, converter, annotation=inspect.Parameter.empty,
                  docstring=None, group=0):
         self.name = name
         self.kind = kind
@@ -3231,6 +3228,8 @@ class str_converter(CConverter):
             # sorry, clinic can't support preallocated buffers
             # for es# and et#
             self.c_default = "NULL"
+        if NoneType in accept and self.c_default == "Py_None":
+            self.c_default = "NULL"
 
     def cleanup(self):
         if self.encoding:
@@ -4433,7 +4432,7 @@ class DSLParser:
                 # mild hack: explicitly support NULL as a default value
                 if isinstance(expr, ast.Name) and expr.id == 'NULL':
                     value = NULL
-                    py_default = 'None'
+                    py_default = '<unrepresentable>'
                     c_default = "NULL"
                 elif (isinstance(expr, ast.BinOp) or
                     (isinstance(expr, ast.UnaryOp) and