[3.8] bpo-37206: Unrepresentable default values no longer represented as None. (GH-13933) (GH-16141)

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.
(cherry picked from commit 279f446)

Co-authored-by: Serhiy Storchaka <[email protected]>

Author: serhiy-storchaka

Lib/test/clinic.test

@@ -92,7 +92,7 @@ test_objects_converter
 [clinic start generated code]*/
 
 PyDoc_STRVAR(test_objects_converter__doc__,
-"test_objects_converter($module, a, b=None, /)\n"
+"test_objects_converter($module, a, b=<unrepresentable>, /)\n"
 "--\n"
 "\n");
 
@@ -126,7 +126,7 @@ exit:
 
 static PyObject *
 test_objects_converter_impl(PyObject *module, PyObject *a, PyObject *b)
-/*[clinic end generated code: output=58009c0e42b4834e input=4cbb3d9edd2a36f3]*/
+/*[clinic end generated code: output=0e461f38d3b2bd08 input=4cbb3d9edd2a36f3]*/
 
 
 /*[clinic input]
@@ -1718,8 +1718,8 @@ test_str_converter
 [clinic start generated code]*/
 
 PyDoc_STRVAR(test_str_converter__doc__,
-"test_str_converter($module, a=None, b=\'ab\', c=\'cd\', d=\'cef\', e=\'gh\',\n"
-"                   f=\'ij\', g=\'kl\', h=\'mn\', /)\n"
+"test_str_converter($module, a=<unrepresentable>, b=\'ab\', c=\'cd\',\n"
+"                   d=\'cef\', e=\'gh\', f=\'ij\', g=\'kl\', h=\'mn\', /)\n"
 "--\n"
 "\n");
 
@@ -1765,7 +1765,7 @@ test_str_converter_impl(PyObject *module, const char *a, const char *b,
                         const char *f, Py_ssize_clean_t f_length,
                         const char *g, Py_ssize_clean_t g_length,
                         const char *h, Py_ssize_clean_t h_length)
-/*[clinic end generated code: output=8415d82c56154307 input=8afe9da8185cd38c]*/
+/*[clinic end generated code: output=ad868ad94a488e32 input=8afe9da8185cd38c]*/
 
 
 /*[clinic input]

Lib/test/test_inspect.py

@@ -2273,8 +2273,8 @@ def p(name): return signature.parameters[name].default
         test_callable(d.dump)
 
         # static method
-        test_callable(str.maketrans)
-        test_callable('abc'.maketrans)
+        test_callable(bytes.maketrans)
+        test_callable(b'abc'.maketrans)
 
         # class method
         test_callable(dict.fromkeys)

Misc/NEWS.d/next/Library/2019-06-09-22-25-03.bpo-37206.2WBg4q.rst

@@ -0,0 +1,2 @@
+Default values which cannot be represented as Python objects no longer
+improperly represented as ``None`` in function signatures.