Validate all variables are defined

src/Language/GraphQL/AST/Document.hs

@@ -24,6 +24,7 @@ module Language.GraphQL.AST.Document
     , Location(..)
     , Name
     , NamedType
+    , Node(..)
     , NonNullType(..)
     , ObjectField(..)
     , OperationDefinition(..)
@@ -70,6 +71,9 @@ instance Ord Location where
         | thisLine > thatLine = GT
         | otherwise = compare thisColumn thatColumn
 
+-- | Contains some tree node with a location.
+data Node a = Node a Location deriving (Eq, Show)
+
 -- ** Document
 
 -- | GraphQL document.
@@ -190,7 +194,7 @@ data FragmentSpread = FragmentSpread Name [Directive] Location
 -- @
 --
 --  Here "id" is an argument for the field "user" and its value is 4.
-data Argument = Argument Name Value Location deriving (Eq,Show)
+data Argument = Argument Name (Node Value) Location deriving (Eq, Show)
 
 -- ** Fragments
 

src/Language/GraphQL/AST/Encoder.hs

@@ -159,7 +159,7 @@ arguments :: Formatter -> [Argument] -> Lazy.Text
 arguments formatter = parensCommas formatter $ argument formatter
 
 argument :: Formatter -> Argument -> Lazy.Text
-argument formatter (Argument name value' _)
+argument formatter (Argument name (Node value' _) _)
     = Lazy.Text.fromStrict name
     <> colon formatter
     <> value formatter value'

src/Language/GraphQL/AST/Parser.hs

@@ -402,7 +402,7 @@ argument = label "Argument" $ do
     location <- getLocation
     name' <- name
     colon
-    value' <- value
+    value' <- valueNode
     pure $ Argument name' value' location
 
 fragmentSpread :: Parser FragmentSpread
@@ -439,6 +439,12 @@ fragmentName = but (symbol "on") *> name <?> "FragmentName"
 typeCondition :: Parser TypeCondition
 typeCondition = symbol "on" *> name <?> "TypeCondition"
 
+valueNode :: Parser (Node Value)
+valueNode = do
+    location <- getLocation
+    value' <- value
+    pure $ Node value' location
+
 value :: Parser Value
 value = Variable <$> variable
     <|> Float <$> try float