Modified __lt__ in Marker class.

Marker class in /voluptuous/schema_builder.py needed to have the __lt__() function
modified in order to compare against regular strings as well.

This will allow the usage of Voluptuous Optional objects as keys in dicts alongside
strings and int.

CHANGELOG.md

@@ -8,6 +8,8 @@
   Treat Python 2 old-style classes like types when validating.
 - [324](https://github.com/alecthomas/voluptuous/pull/324):
   Default values MUST now pass validation just as any regular value. This is a backward incompatible change if a schema uses default values that don't pass validation against the specified schema.
+- [328](https://github.com/alecthomas/voluptuous/pull/328):
+  Modified __lt__ in Marker class to allow comparison with non Marker objects, such as str and int
 
 ## [0.10.5]
 

voluptuous/schema_builder.py

@@ -953,7 +953,9 @@ def __repr__(self):
         return repr(self.schema)
 
     def __lt__(self, other):
-        return self.schema < other.schema
+        if isinstance(other, Marker):
+            return self.schema < other.schema
+        return self.schema < other
 
     def __hash__(self):
         return hash(self.schema)

voluptuous/tests/tests.md

@@ -266,3 +266,8 @@ Ensure that subclasses of Invalid of are raised as is.
     ...   exc = e
     >>> exc.errors[0].__class__.__name__
     'SpecialInvalid'
+
+Ensure that Optional('Classification') < 'Name' will return True instead of throwing an AttributeError
+
+    >>> Optional('Classification') < 'Name'
+    True

voluptuous/tests/tests.py

@@ -1137,3 +1137,22 @@ def test_self_all():
 def test_SomeOf_on_bounds_assertion():
     with raises(AssertionError, 'when using "SomeOf" you should specify at least one of min_valid and max_valid'):
         SomeOf(validators=[])
+
+
+def test_sorting_dict_with_voluptuous_objects_and_str():
+    schema_with_voluptuous_object = {
+        'Name': 'Mo',
+        'ExecutionTimestamp': 'Today',
+        Optional('Classification'): [Any(['A+', 'B+'])]
+    }
+    schema_without_voluptuous_object = {
+        'Name': 'Mo',
+        'ExecutionTimestamp': 'Today',
+        'Classification': [Any(['A+', 'B+'])]
+    }
+
+    assert_true(sorted(schema_with_voluptuous_object), sorted(schema_without_voluptuous_object))
+
+
+def test_comparing_voluptuous_object_to_str():
+    assert_true(Optional('Classification') < 'Name')