Add ValidatorMixin.validator_for

Helps subclasses / mixersin be able to override where validators look for their
validator functions.

Author: Julian

jsonschema.py

@@ -267,6 +267,10 @@ def check_schema(cls, schema):
         for error in cls(cls.META_SCHEMA).iter_errors(schema):
             raise SchemaError.create_from(error)
 
+    def validator_for(self, validator):
+        validator_attr = "validate_%s" % (validator.lstrip("$"),)
+        return getattr(self, validator_attr, None)
+
     def iter_errors(self, instance, _schema=None):
         if _schema is None:
             _schema = self.schema
@@ -279,9 +283,7 @@ def iter_errors(self, instance, _schema=None):
                 validators = iteritems(_schema)
 
             for k, v in validators:
-                validator_attr = "validate_%s" % (k.lstrip("$"),)
-                validator = getattr(self, validator_attr, None)
-
+                validator = self.validator_for(k)
                 if validator is None:
                     continue
 

tests.py

@@ -834,6 +834,24 @@ class Validator(ValidatorMixin):
         self.assertTrue(Validator.validate_ref.called)
         self.assertFalse(Validator.validate_type.called)
 
+    def test_validator_for(self):
+        class Validator(ValidatorMixin):
+            validate_type = mock.Mock()
+        validator = Validator({})
+        self.assertEqual(
+            validator.validator_for("type"), validator.validate_type,
+        )
+
+    def test_redefined_validator_for(self):
+        v = mock.Mock(return_value=[])
+
+        class Validator(ValidatorMixin):
+            def validator_for(self, validator):
+                return v
+
+        Validator({"foo" : 12}).validate(42)
+        v.assert_called_once_with(12, 42, {"foo" : 12})
+
 
 class TestRefResolver(unittest.TestCase):