Validate input fields have unique names

src/Language/GraphQL/AST/Document.hs

@@ -236,7 +236,7 @@ data ConstValue
 -- | Key-value pair.
 --
 -- A list of 'ObjectField's represents a GraphQL object type.
-data ObjectField a = ObjectField Name a
+data ObjectField a = ObjectField Name a Location
     deriving (Eq, Show)
 
 -- ** Variables

src/Language/GraphQL/AST/Encoder.hs

@@ -220,8 +220,8 @@ fromConstValue (ConstEnum x) = Enum x
 fromConstValue (ConstList x) = List $ fromConstValue <$> x
 fromConstValue (ConstObject x) = Object $ fromConstObjectField <$> x
   where
-    fromConstObjectField (ObjectField key value') =
-        ObjectField key $ fromConstValue value'
+    fromConstObjectField (ObjectField key value' location) =
+        ObjectField key (fromConstValue value') location
 
 booleanValue :: Bool -> Lazy.Text
 booleanValue True  = "true"
@@ -290,7 +290,7 @@ objectValue formatter = intercalate $ objectField formatter
         . fmap f
 
 objectField :: Formatter -> ObjectField Value -> Lazy.Text
-objectField formatter (ObjectField name value') =
+objectField formatter (ObjectField name value' _) =
     Lazy.Text.fromStrict name <> colon formatter <> value formatter value'
 
 -- | Converts a 'Type' a type into a string.

src/Language/GraphQL/AST/Parser.hs

@@ -487,11 +487,12 @@ nullValue :: Parser Text
 nullValue = symbol "null" <?> "NullValue"
 
 objectField :: Parser a -> Parser (ObjectField a)
-objectField valueParser = ObjectField
-    <$> name
-    <* colon
-    <*> valueParser
-    <?> "ObjectField"
+objectField valueParser = label "ObjectField" $ do
+    location <- getLocation
+    fieldName <- name
+    colon
+    fieldValue <- valueParser
+    pure $ ObjectField fieldName fieldValue location
 
 variableDefinitions :: Parser [VariableDefinition]
 variableDefinitions = listOptIn parens variableDefinition