fix: max-affected preference not failing for rpc with strict handling

src/PostgREST/Error.hs

@@ -96,6 +96,7 @@ data ApiRequestError
   | MaxAffectedViolationError Integer
   | InvalidResourcePath
   | OpenAPIDisabled
+  | MaxAffectedRpcViolation
   deriving Show
 
 data QPError = QPError Text Text
@@ -138,6 +139,7 @@ instance PgrstError ApiRequestError where
   status MaxAffectedViolationError{} = HTTP.status400
   status InvalidResourcePath         = HTTP.status404
   status OpenAPIDisabled             = HTTP.status404
+  status MaxAffectedRpcViolation     = HTTP.status400
 
   headers _ = mempty
 
@@ -184,6 +186,7 @@ instance ErrorBody ApiRequestError where
   code InvalidResourcePath         = "PGRST125"
   code OpenAPIDisabled             = "PGRST126"
   code NotImplemented{}            = "PGRST127"
+  code MaxAffectedRpcViolation     = "PGRST128"
 
   -- MESSAGE: Text
   message (QueryParamError (QPError msg _)) = msg
@@ -209,6 +212,7 @@ instance ErrorBody ApiRequestError where
   message InvalidResourcePath            = "Invalid path specified in request URL"
   message OpenAPIDisabled                = "Root endpoint metadata is disabled"
   message (NotImplemented _)             = "Feature not implemented"
+  message MaxAffectedRpcViolation        = "Function must return SETOF or TABLE when max-affected preference is used with handling=strict"
 
   -- DETAILS: Maybe JSON.Value
   details (QueryParamError (QPError _ dets)) = Just $ JSON.String dets

src/PostgREST/Plan.hs

@@ -72,7 +72,8 @@ import PostgREST.SchemaCache.Routine         (MediaHandler (..),
                                               RoutineParam (..),
                                               funcReturnsCompositeAlias,
                                               funcReturnsScalar,
-                                              funcReturnsSetOfScalar)
+                                              funcReturnsSetOfScalar,
+                                              funcReturnsSingle)
 import PostgREST.SchemaCache.Table           (Column (..), Table (..),
                                               TablesMap,
                                               tableColumnsList,
@@ -172,7 +173,7 @@ mutateReadPlan  mutation apiRequest@ApiRequest{iPreferences=Preferences{..},..}
   return $ MutateReadPlan rPlan mPlan SQL.Write handler mediaType mutation qi
 
 callReadPlan :: QualifiedIdentifier -> AppConfig -> SchemaCache -> ApiRequest -> InvokeMethod -> Either Error CallReadPlan
-callReadPlan identifier conf sCache apiRequest@ApiRequest{iPreferences=Preferences{preferHandling, invalidPrefs},..} invMethod = do
+callReadPlan identifier conf sCache apiRequest@ApiRequest{iPreferences=Preferences{preferHandling, invalidPrefs, preferMaxAffected},..} invMethod = do
   let paramKeys = case invMethod of
         InvRead _ -> S.fromList $ fst <$> qsParams'
         Inv       -> iColumns
@@ -192,10 +193,15 @@ callReadPlan identifier conf sCache apiRequest@ApiRequest{iPreferences=Preferenc
       cPlan = callPlan proc apiRequest paramKeys args rPlan
   (handler, mediaType)  <- mapLeft ApiRequestError $ negotiateContent conf apiRequest relIdentifier iAcceptMediaType (dbMediaHandlers sCache) (hasDefaultSelect rPlan)
   if not (null invalidPrefs) && preferHandling == Just Strict then Left $ ApiRequestError $ InvalidPreferences invalidPrefs else Right ()
+  failMaxAffectedRpcReturnsSingle (preferMaxAffected, preferHandling) proc
   return $ CallReadPlan rPlan cPlan txMode proc handler mediaType invMethod identifier
   where
     qsParams' = QueryParams.qsParams iQueryParams
 
+    failMaxAffectedRpcReturnsSingle :: (Maybe PreferMaxAffected, Maybe PreferHandling) -> Routine -> Either Error ()
+    failMaxAffectedRpcReturnsSingle (Just (PreferMaxAffected _), Just Strict) rout = if funcReturnsSingle rout then Left $ ApiRequestError MaxAffectedRpcViolation else Right ()
+    failMaxAffectedRpcReturnsSingle _ _ = Right ()
+
 hasDefaultSelect :: ReadPlanTree -> Bool
 hasDefaultSelect (Node ReadPlan{select=[CoercibleSelectField{csField=CoercibleField{cfName}}]} []) = cfName == "*"
 hasDefaultSelect _ = False