fix: Return 204 No Content without Content-Type for RPCs returning VOID

Resolves #2001

BREAKING CHANGE: Previously, those RPCs would return "null" as a body with Content-Type: application/json.

src/PostgREST/App.hs

@@ -469,9 +469,12 @@ handleInvoke invMethod proc context@RequestContext{..} = do
       RangeQuery.rangeStatusHeader iTopLevelRange queryTotal tableTotal
 
   failNotSingular iAcceptContentType queryTotal $
-    response status
-      (contentTypeHeaders context ++ [contentRange])
-      (if invMethod == InvHead then mempty else LBS.fromStrict body)
+    if Proc.procReturnsVoid proc then
+      response HTTP.status204 [contentRange] mempty
+    else
+      response status
+        (contentTypeHeaders context ++ [contentRange])
+        (if invMethod == InvHead then mempty else LBS.fromStrict body)
 
 handleOpenApi :: Bool -> Schema -> RequestContext -> DbHandler Wai.Response
 handleOpenApi headersOnly tSchema (RequestContext conf@AppConfig{..} dbStructure apiRequest ctxPgVersion) = do

src/PostgREST/DbStructure.hs

@@ -202,6 +202,7 @@ decodeProcs =
                   <$> column HD.text
                   <*> column HD.text
                   <*> column HD.bool
+                  <*> column HD.bool
                   <*> column HD.bool)
               <*> (parseVolatility <$> column HD.char)
               <*> column HD.bool
@@ -209,10 +210,11 @@ decodeProcs =
     addKey :: ProcDescription -> (QualifiedIdentifier, ProcDescription)
     addKey pd = (QualifiedIdentifier (pdSchema pd) (pdName pd), pd)
 
-    parseRetType :: Text -> Text -> Bool -> Bool -> RetType
-    parseRetType schema name isSetOf isComposite
-      | isSetOf   = SetOf pgType
-      | otherwise = Single pgType
+    parseRetType :: Text -> Text -> Bool -> Bool -> Bool -> Maybe RetType
+    parseRetType schema name isSetOf isComposite isVoid
+      | isVoid    = Nothing
+      | isSetOf   = Just (SetOf pgType)
+      | otherwise = Just (Single pgType)
       where
         qi = QualifiedIdentifier schema name
         pgType
@@ -287,6 +289,7 @@ procsSqlQuery = [q|
      -- if any TABLE, INOUT or OUT arguments present, treat as composite
      or COALESCE(proargmodes::text[] && '{t,b,o}', false)
     ) AS rettype_is_composite,
+    ('pg_catalog.void'::regtype = t.oid) AS rettype_is_void,
     p.provolatile,
     p.provariadic > 0 as hasvariadic
   FROM pg_proc p

src/PostgREST/DbStructure/Proc.hs

@@ -10,6 +10,7 @@ module PostgREST.DbStructure.Proc
   , RetType(..)
   , procReturnsScalar
   , procReturnsSingle
+  , procReturnsVoid
   , procTableName
   ) where
 
@@ -42,7 +43,7 @@ data ProcDescription = ProcDescription
   , pdName        :: Text
   , pdDescription :: Maybe Text
   , pdParams      :: [ProcParam]
-  , pdReturnType  :: RetType
+  , pdReturnType  :: Maybe RetType
   , pdVolatility  :: ProcVolatility
   , pdHasVariadic :: Bool
   }
@@ -69,17 +70,22 @@ type ProcsMap = M.HashMap QualifiedIdentifier [ProcDescription]
 
 procReturnsScalar :: ProcDescription -> Bool
 procReturnsScalar proc = case proc of
-  ProcDescription{pdReturnType = (Single Scalar)} -> True
-  ProcDescription{pdReturnType = (SetOf Scalar)}  -> True
-  _                                               -> False
+  ProcDescription{pdReturnType = Just (Single Scalar)} -> True
+  ProcDescription{pdReturnType = Just (SetOf Scalar)}  -> True
+  _                                                    -> False
 
 procReturnsSingle :: ProcDescription -> Bool
 procReturnsSingle proc = case proc of
-  ProcDescription{pdReturnType = (Single _)} -> True
-  _                                          -> False
+  ProcDescription{pdReturnType = Just (Single _)} -> True
+  _                                               -> False
+
+procReturnsVoid :: ProcDescription -> Bool
+procReturnsVoid proc = case proc of
+  ProcDescription{pdReturnType = Nothing} -> True
+  _                                       -> False
 
 procTableName :: ProcDescription -> Maybe TableName
 procTableName proc = case pdReturnType proc of
-  SetOf  (Composite qi) -> Just $ qiName qi
-  Single (Composite qi) -> Just $ qiName qi
-  _                     -> Nothing
+  Just (SetOf  (Composite qi)) -> Just $ qiName qi
+  Just (Single (Composite qi)) -> Just $ qiName qi
+  _                            -> Nothing