Handle $ref defined types errors

We use $ref in the schema to allow us to specify multiple type, eg
command, it can be a string or a list of strings.

It required some extra parsing to retrieve a helpful type to display
in our error message rather than 'string or string'. Which while
correct, is not helpful. We value helpful.

Signed-off-by: Mazz Mosley <mazz@houseofmnowster.com>

compose/config/validation.py

@@ -55,6 +55,16 @@ def process_errors(errors):
     def _clean_error_message(message):
         return message.replace("u'", "'")
 
+    def _parse_valid_types_from_schema(schema):
+        """
+        Our defined types using $ref in the schema require some extra parsing
+        retrieve a helpful type for error message display.
+        """
+        if '$ref' in schema:
+            return schema['$ref'].replace("#/definitions/", "").replace("_", " ")
+        else:
+            return str(schema['type'])
+
     root_msgs = []
     invalid_keys = []
     required = []
@@ -93,9 +103,11 @@ def process_errors(errors):
                     required.append(_clean_error_message(error.message))
             elif error.validator == 'oneOf':
                 config_key = error.path[0]
-                valid_types = [context.validator_value for context in error.context]
+
+                valid_types = [_parse_valid_types_from_schema(schema) for schema in error.schema['oneOf']]
                 valid_type_msg = " or ".join(valid_types)
-                type_errors.append("Service '{}' configuration key '{}' contains an invalid type, it should be either {}".format(
+
+                type_errors.append("Service '{}' configuration key '{}' contains an invalid type, valid types are {}".format(
                     service_name, config_key, valid_type_msg)
                 )
             elif error.validator == 'type':

tests/unit/config_test.py

@@ -160,6 +160,19 @@ class ConfigTest(unittest.TestCase):
                 )
             )
 
+    def test_invalid_list_of_strings_format(self):
+        expected_error_msg = "'command' contains an invalid type, valid types are string or list of strings"
+        with self.assertRaisesRegexp(ConfigurationError, expected_error_msg):
+            config.load(
+                config.ConfigDetails(
+                    {
+                        'web': {'build': '.', 'command': [1]}
+                    },
+                    'tests/fixtures/extends',
+                    'filename.yml'
+                )
+            )
+
 
 class InterpolationTest(unittest.TestCase):
     @mock.patch.dict(os.environ)