Fix additionalItems behavior when items is not in tuple form.

Author: gazpachoking

jsonschema.py

@@ -447,6 +447,8 @@ def validate_items(self, items, instance, schema):
     def validate_additionalItems(self, aI, instance, schema):
         if not self.is_type(instance, "array"):
             return
+        if not self.is_type(schema.get("items"), "array"):
+            return
 
         if self.is_type(aI, "object"):
             for item in instance[len(schema):]:
@@ -455,7 +457,7 @@ def validate_additionalItems(self, aI, instance, schema):
         elif not aI and len(instance) > len(schema.get("items", [])):
             error = "Additional items are not allowed (%s %s unexpected)"
             yield ValidationError(
-                error % _extras_msg(instance[len(schema) - 1:])
+                error % _extras_msg(instance[len(schema.get("items", [])):])
             )
 
     def validate_minimum(self, minimum, instance, schema):

tests.py

@@ -320,6 +320,9 @@ def test_additionalItems_allowed_by_default(self):
     def test_additionalItems_ignores_nonarrays(self):
         validate(None, {"additionalItems" : False})
 
+    def test_additionalItems_ignored_when_items_is_not_tuple(self):
+        validate([1, 2], {"additionalItems" : False})
+
     @parametrized(
         ("false_by_default", "valid", {}, {}),
         ("false_explicit", "valid", {"required" : False}, {}),
@@ -676,11 +679,13 @@ def test_dependencies_failure_has_single_element_not_list(self):
         self.assertEqual(message, "%r is a dependency of %r" % (on, depend))
 
     def test_additionalItems_single_failure(self):
-        message = self.message_for([2], {"additionalItems" : False})
+        message = self.message_for([2],
+            {"items" : [], "additionalItems" : False})
         self.assertIn("(2 was unexpected)", message)
 
     def test_additionalItems_multiple_failures(self):
-        message = self.message_for([1, 2, 3], {"additionalItems" : False})
+        message = self.message_for([1, 2, 3],
+            {"items" : [], "additionalItems" : False})
         self.assertIn("(1, 2, 3 were unexpected)", message)
 
     def test_additionalProperties_single_failure(self):