Fix Printer Properties crash for None option values

options.py

@@ -63,6 +63,11 @@ def __str__ (self):
                                                    self.UNITS_DEFAULT))
 
 def OptionWidget(name, v, s, on_change):
+    if v is None:
+        # A queue default that is present but unset arrives with the IPP
+        # "no-value" tag, which pycups returns as None.  Treat it as empty so
+        # the conversions below take their existing unconvertible-value path.
+        v = ""
     if isinstance(v, list):
         # XXX
         if isinstance(s, list):

test_options.py

@@ -0,0 +1,74 @@
+#!/usr/bin/python3
+
+## system-config-printer
+
+## Copyright (C) 2015 Red Hat, Inc.
+## Author:
+##     Ayush Singh <ayushsinghceee@gmail.com>
+
+## This program is free software; you can redistribute it and/or modify
+## it under the terms of the GNU General Public License as published by
+## the Free Software Foundation; either version 2 of the License, or
+## (at your option) any later version.
+
+## This program is distributed in the hope that it will be useful,
+## but WITHOUT ANY WARRANTY; without even the implied warranty of
+## MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+## GNU General Public License for more details.
+
+## You should have received a copy of the GNU General Public License
+## along with this program; if not, write to the Free Software
+## Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA  02110-1301, USA.
+
+import os
+
+import gi
+gi.require_version('Gtk', '3.0')
+import pytest
+
+import options
+
+has_display = bool(os.environ.get('DISPLAY') or
+                   os.environ.get('WAYLAND_DISPLAY'))
+pytestmark = pytest.mark.skipif(not has_display,
+                                reason="needs a GTK display connection")
+
+NAME = "job-cancel-after"
+RANGE = (0, 2147483647)
+
+
+def on_change(option):
+    pass
+
+
+def test_value_from_cups():
+    option = options.OptionWidget(NAME, 10800, RANGE, on_change)
+    assert isinstance(option, options.OptionNumeric)
+    assert option.get_current_value() == 10800
+    assert not option.is_changed()
+
+
+def test_boundary_value():
+    option = options.OptionWidget(NAME, 0, RANGE, on_change)
+    assert isinstance(option, options.OptionNumeric)
+    assert option.get_current_value() == 0
+    assert not option.is_changed()
+
+
+def test_no_value_with_range_supported():
+    """A queue default sent with the IPP 'no-value' tag becomes None."""
+    option = options.OptionWidget(NAME, None, RANGE, on_change)
+    assert option.get_current_value() == ""
+    assert not option.is_changed()
+
+
+def test_no_value_without_supported():
+    option = options.OptionWidget(NAME, None, "", on_change)
+    assert isinstance(option, options.OptionText)
+    assert option.get_current_value() == ""
+    assert not option.is_changed()
+
+
+def test_no_value_with_supported_choices():
+    option = options.OptionWidget(NAME, None, ['none', 'day-time'], on_change)
+    assert isinstance(option, options.OptionSelectOne)