Fix oneOf validator parser to correctly process uniqueItems errors

Signed-off-by: Joffrey F <joffrey@docker.com>

compose/config/validation.py

@@ -325,7 +325,6 @@ def _parse_oneof_validator(error):
     """
     types = []
     for context in error.context:
-
         if context.validator == 'oneOf':
             _, error_msg = _parse_oneof_validator(context)
             return path_string(context.path), error_msg
@@ -337,6 +336,13 @@ def _parse_oneof_validator(error):
             invalid_config_key = parse_key_from_error_msg(context)
             return (None, "contains unsupported option: '{}'".format(invalid_config_key))
 
+        if context.validator == 'uniqueItems':
+            return (
+                path_string(context.path) if context.path else None,
+                "contains non-unique items, please remove duplicates from {}".format(
+                    context.instance),
+            )
+
         if context.path:
             return (
                 path_string(context.path),
@@ -345,13 +351,6 @@ def _parse_oneof_validator(error):
                     _parse_valid_types_from_validator(context.validator_value)),
             )
 
-        if context.validator == 'uniqueItems':
-            return (
-                None,
-                "contains non unique items, please remove duplicates from {}".format(
-                    context.instance),
-            )
-
         if context.validator == 'type':
             types.append(context.validator_value)
 

tests/unit/config/config_test.py

@@ -581,6 +581,20 @@ class ConfigTest(unittest.TestCase):
 
             assert 'Invalid service name \'mong\\o\'' in excinfo.exconly()
 
+    def test_config_duplicate_cache_from_values_validation_error(self):
+        with pytest.raises(ConfigurationError) as exc:
+            config.load(
+                build_config_details({
+                    'version': '2.3',
+                    'services': {
+                        'test': {'build': {'context': '.', 'cache_from': ['a', 'b', 'a']}}
+                    }
+
+                })
+            )
+
+        assert 'build.cache_from contains non-unique items' in exc.exconly()
+
     def test_load_with_multiple_files_v1(self):
         base_file = config.ConfigFile(
             'base.yaml',
@@ -2751,11 +2765,12 @@ class PortsTest(unittest.TestCase):
 
     def check_config(self, cfg):
         config.load(
-            build_config_details(
-                {'web': dict(image='busybox', **cfg)},
-                'working_dir',
-                'filename.yml'
-            )
+            build_config_details({
+                'version': '2.3',
+                'services': {
+                    'web': dict(image='busybox', **cfg)
+                },
+            }, 'working_dir', 'filename.yml')
         )