Fix "variable is not used" error

src/Language/GraphQL/Validate/Rules.hs

@@ -618,6 +618,10 @@ noUndefinedVariablesRule =
         , "\"."
         ]
 
+-- Used to find the difference between defined and used variables. The first
+-- argument are variables defined in the operation, the second argument are
+-- variables used in the query. It should return the difference between these
+-- 2 sets.
 type UsageDifference
     = HashMap Full.Name [Full.Location]
     -> HashMap Full.Name [Full.Location]
@@ -664,11 +668,26 @@ variableUsageDifference difference errorMessage = OperationDefinitionRule $ \cas
         = filterSelections' selections
         >>= lift . mapReaderT (<> mapDirectives directives') . pure
     findDirectiveVariables (Full.Directive _ arguments _) = mapArguments arguments
-    mapArguments = Seq.fromList . mapMaybe findArgumentVariables
+
+    mapArguments = Seq.fromList . (>>= findArgumentVariables)
     mapDirectives = foldMap findDirectiveVariables
-    findArgumentVariables (Full.Argument _ Full.Node{ node = Full.Variable value', ..} _) =
-        Just (value', [location])
-    findArgumentVariables _ = Nothing
+
+    findArgumentVariables (Full.Argument _ Full.Node{node = value, ..} _) =
+        findValueVariables location value
+
+    findValueVariables location (Full.Variable value') = [(value', [location])]
+    findValueVariables location (Full.List values) =
+        values
+            >>= (\(Full.Node{node = value}) -> findValueVariables location value)
+    findValueVariables _ (Full.Object fields) =
+        fields
+            >>= ( \( Full.ObjectField
+                        { location = location
+                        , value = Full.Node{node = value}
+                        }
+                    ) -> findValueVariables location value
+                )
+    findValueVariables _ _ = []
     makeError operationName (variableName, locations') = Error
         { message = errorMessage operationName variableName
         , locations = locations'

tests/Language/GraphQL/Validate/RulesSpec.hs

@@ -18,7 +18,7 @@ import Language.GraphQL.Type
 import qualified Language.GraphQL.Type.In as In
 import qualified Language.GraphQL.Type.Out as Out
 import Language.GraphQL.Validate
-import Test.Hspec (Spec, context, describe, it, shouldBe, shouldContain)
+import Test.Hspec (Spec, context, describe, it, shouldBe, shouldContain, xit)
 import Text.Megaparsec (parse, errorBundlePretty)
 
 petSchema :: Schema IO
@@ -560,7 +560,7 @@ spec =
                         }
                  in validate queryString `shouldBe` [expected]
 
-        context "noUnusedVariablesRule" $
+        context "noUnusedVariablesRule" $ do
             it "rejects unused variables" $
                 let queryString = [gql|
                   query variableUnused($atOtherHomes: Boolean) {
@@ -577,6 +577,16 @@ spec =
                         }
                  in validate queryString `shouldBe` [expected]
 
+            xit "detects variables in properties of input objects" $
+                let queryString = [gql|
+                  query withVar ($name: String!) {
+                    findDog (complex: { name: $name }) {
+                      name
+                    }
+                  }
+                |]
+                 in validate queryString `shouldBe` []
+
         context "uniqueInputFieldNamesRule" $
             it "rejects duplicate fields in input objects" $
                 let queryString = [gql|