Issue #1028: Tk returns invalid Unicode null in %A: UnicodeDecodeError.

With Tk < 8.5 _tkinter.c:PythonCmd() raised UnicodeDecodeError, caused IDLE to
exit.  Converted to valid Unicode null in PythonCmd().

Lib/idlelib/NEWS.txt

 What's New in IDLE 3.1.4?
 =========================
 
-*Release date: XX-XXX-XX*
+*Release date: 15-May-11*
+
+- Issue #1028: Ctrl-space binding to show completions was causing IDLE to exit.
+  Tk < 8.5 was sending invalid Unicode null; replaced with valid null.
 
 - <Home> toggle failing on Tk 8.5, causing IDLE exits and strange selection
   behavior. Issue 4676.  Improve selection extension behaviour.
-- <Home> toggle non-functional when NumLock set on Windows.  Issue 3851.
 
+- <Home> toggle non-functional when NumLock set on Windows.  Issue 3851.
 
 
 What's New in IDLE 3.1b1?
 =========================
 
-*Release date: XX-XXX-09*
+*Release date: 06-May-09*
 
 - Use of 'filter' in keybindingDialog.py was causing custom key assignment to
   fail.  Patch 5707 amaury.forgeotdarc.

Misc/NEWS

@@ -69,6 +69,10 @@ Core and Builtins
 Library
 -------
 
+- Issue #1028: Tk returns invalid Unicode null in %A: UnicodeDecodeError.
+  With Tk < 8.5 _tkinter.c:PythonCmd() raised UnicodeDecodeError, caused
+  IDLE to exit.  Converted to valid Unicode null in PythonCmd().
+
 - Issue #10419: Fix build_scripts command of distutils to handle correctly
   non-ASCII scripts. Open and write the script in binary mode, but ensure that
   the shebang is decodable from UTF-8 and from the encoding of the script.

Modules/_tkinter.c

@@ -2023,7 +2023,19 @@ PythonCmd(ClientData clientData, Tcl_Interp *interp, int argc, char *argv[])
 
     for (i = 0; i < (argc - 1); i++) {
         PyObject *s = PyUnicode_FromString(argv[i + 1]);
-        if (!s || PyTuple_SetItem(arg, i, s)) {
+        if (!s) {
+            /* Is Tk leaking 0xC080 in %A - a "modified" utf-8 null? */
+            if (PyErr_ExceptionMatches(PyExc_UnicodeDecodeError) &&
+                !strcmp(argv[i + 1], "\xC0\x80")) {
+                PyErr_Clear();
+                /* Convert to "strict" utf-8 null */
+                s = PyUnicode_FromString("\0");
+            } else {
+                Py_DECREF(arg);
+                return PythonCmd_Error(interp);
+            }
+        }
+        if (PyTuple_SetItem(arg, i, s)) {
             Py_DECREF(arg);
             return PythonCmd_Error(interp);
         }