From 4a3b4cb16d7da9c356b514ab48bdc0e527acd377 Mon Sep 17 00:00:00 2001
From: Eugen Wissner <belka@caraus.de>
Date: Fri, 6 Nov 2020 08:33:51 +0100
Subject: Fix singleFieldSubscriptionsRule fragment lookup

singleFieldSubscriptionsRule picks up a wrong fragment definition.
---
 src/Language/GraphQL/Validate/Rules.hs | 33 ++++++++++++++++++---------------
 1 file changed, 18 insertions(+), 15 deletions(-)

(limited to 'src/Language/GraphQL')

diff --git a/src/Language/GraphQL/Validate/Rules.hs b/src/Language/GraphQL/Validate/Rules.hs
index b794b64..c67df1c 100644
--- a/src/Language/GraphQL/Validate/Rules.hs
+++ b/src/Language/GraphQL/Validate/Rules.hs
@@ -50,6 +50,7 @@ import Data.HashSet (HashSet)
 import qualified Data.HashSet as HashSet
 import Data.List (groupBy, sortBy, sortOn)
 import Data.Maybe (isNothing, mapMaybe)
+import Data.List.NonEmpty (NonEmpty)
 import Data.Ord (comparing)
 import Data.Sequence (Seq(..), (|>))
 import qualified Data.Sequence as Seq
@@ -127,10 +128,10 @@ singleFieldSubscriptionsRule = OperationDefinitionRule $ \case
             1 -> lift mempty
             _
                 | Just name <- name' -> pure $ Error
-                    { message = unwords
-                        [ "Subscription"
+                    { message = concat
+                        [ "Subscription \""
                         , Text.unpack name
-                        , "must select only one top level field."
+                        , "\" must select only one top level field."
                         ]
                     , locations = [location']
                     }
@@ -172,10 +173,6 @@ singleFieldSubscriptionsRule = OperationDefinitionRule $ \case
     skip (Full.Directive "include" [Full.Argument "if" (Full.Node argumentValue _) _] _) =
         Full.Boolean False == argumentValue
     skip _ = False
-    findFragmentDefinition (Full.ExecutableDefinition executableDefinition) Nothing
-        | Full.DefinitionFragment fragmentDefinition <- executableDefinition =
-            Just fragmentDefinition
-    findFragmentDefinition _ accumulator = accumulator
     collectFromFragment typeCondition selectionSet accumulator = do
         types' <- lift $ asks $ Schema.types . schema
         schema' <- lift $ asks schema
@@ -189,7 +186,7 @@ singleFieldSubscriptionsRule = OperationDefinitionRule $ \case
     collectFromSpread fragmentName accumulator = do
         modify $ HashSet.insert fragmentName
         ast' <- lift $ asks ast
-        case foldr findFragmentDefinition Nothing ast' of
+        case findFragmentDefinition fragmentName ast' of
             Nothing -> pure accumulator
             Just (Full.FragmentDefinition _ typeCondition _ selectionSet _) ->
                 collectFromFragment typeCondition selectionSet accumulator
@@ -493,18 +490,24 @@ noFragmentCyclesRule = FragmentDefinitionRule $ \case
         (accumulator <>) <$> collectFields selections
     forField accumulator (Full.Field _ _ _ _ selections _) =
         (accumulator <>) <$> collectFields selections
-    findFragmentDefinition n (Full.ExecutableDefinition executableDefinition) Nothing
-        | Full.DefinitionFragment fragmentDefinition <- executableDefinition
-        , Full.FragmentDefinition fragmentName _ _ _ _ <- fragmentDefinition
-        , fragmentName == n = Just fragmentDefinition
-    findFragmentDefinition _ _ accumulator = accumulator
-    collectFromSpread _fragmentName accumulator = do
+    collectFromSpread fragmentName accumulator = do
         ast' <- lift $ asks ast
-        case foldr (findFragmentDefinition _fragmentName) Nothing ast' of
+        case findFragmentDefinition fragmentName ast' of
             Nothing -> pure accumulator
             Just (Full.FragmentDefinition _ _ _ selections _) ->
                 (accumulator <>) <$> collectFields selections
 
+findFragmentDefinition :: Text
+    -> NonEmpty Full.Definition
+    -> Maybe Full.FragmentDefinition
+findFragmentDefinition fragmentName = foldr compareDefinition Nothing
+  where
+    compareDefinition (Full.ExecutableDefinition executableDefinition) Nothing
+        | Full.DefinitionFragment fragmentDefinition <- executableDefinition
+        , Full.FragmentDefinition anotherName _ _ _ _ <- fragmentDefinition
+        , anotherName == fragmentName = Just fragmentDefinition
+    compareDefinition _ accumulator = accumulator
+
 -- | Fields and directives treat arguments as a mapping of argument name to
 -- value. More than one argument with the same name in an argument set is
 -- ambiguous and invalid.
-- 
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