fix: bad M2M embed on RPC

src/PostgREST/Error.hs

@@ -209,7 +209,7 @@ compressedRel Relationship{..} =
     : case relCardinality of
         M2M Junction{..} -> [
             "cardinality" .= ("many-to-many" :: Text)
-          , "relationship" .= (qiName junTable <> " using " <> junConstraint1 <> fmtEls (snd <$> junColumns1) <> " and " <> junConstraint2 <> fmtEls (snd <$> junColumns2))
+          , "relationship" .= (qiName junTable <> " using " <> junConstraint1 <> fmtEls (snd <$> junColsSource) <> " and " <> junConstraint2 <> fmtEls (snd <$> junColsTarget))
           ]
         M2O cons relColumns -> [
             "cardinality" .= ("many-to-one" :: Text)

src/PostgREST/Plan.hs

@@ -399,7 +399,7 @@ mutatePlan mutation qi ApiRequest{..} sCache readReq = mapLeft ApiRequestError $
     returnings =
       if iPreferRepresentation == None
         then []
-        else returningCols readReq pkCols
+        else inferColsEmbedNeeds readReq pkCols
     pkCols = maybe mempty tablePKCols $ HM.lookup qi $ dbTables sCache
     logic = map snd qsLogic
     rootOrder = maybe [] snd $ find (\(x, _) -> null x) qsOrder
@@ -413,7 +413,7 @@ callPlan proc apiReq readReq = FunctionCall {
 , funCArgs = payRaw <$> iPayload apiReq
 , funCScalar = procReturnsScalar proc
 , funCMultipleCall = iPreferParameters apiReq == Just MultipleObjects
-, funCReturning = returningCols readReq []
+, funCReturning = inferColsEmbedNeeds readReq []
 }
   where
     paramsAsSingleObject = iPreferParameters apiReq == Just SingleObject
@@ -424,14 +424,15 @@ callPlan proc apiReq readReq = FunctionCall {
       prms  -> KeyParams $ specifiedParams prms
     specifiedParams = filter (\x -> ppName x `S.member` iColumns apiReq)
 
-returningCols :: ReadPlanTree -> [FieldName] -> [FieldName]
-returningCols rr@(Node _ forest) pkCols
+-- | Infers the columns needed for an embed to be successful after a mutation or a function call.
+inferColsEmbedNeeds :: ReadPlanTree -> [FieldName] -> [FieldName]
+inferColsEmbedNeeds (Node ReadPlan{select} forest) pkCols
   -- if * is part of the select, we must not add pk or fk columns manually -
   -- otherwise those would be selected and output twice
   | "*" `elem` fldNames = ["*"]
   | otherwise           = returnings
   where
-    fldNames = fstFieldNames rr
+    fldNames = (\((fld, _), _, _) -> fld) <$> select
     -- Without fkCols, when a mutatePlan to
     -- /projects?select=name,clients(name) occurs, the RETURNING SQL part would
     -- be `RETURNING name`(see QueryBuilder).  This would make the embedding
@@ -445,8 +446,8 @@ returningCols rr@(Node _ forest) pkCols
           Just $ fst <$> cols
         Node ReadPlan{relToParent=Just Relationship{relCardinality=O2O _ cols}} _ ->
           Just $ fst <$> cols
-        Node ReadPlan{relToParent=Just Relationship{relCardinality=M2M Junction{junColumns1, junColumns2}}} _ ->
-          Just $ (fst <$> junColumns1) ++ (fst <$> junColumns2)
+        Node ReadPlan{relToParent=Just Relationship{relCardinality=M2M Junction{junColsSource=cols}}} _ ->
+          Just $ fst <$> cols
         Node ReadPlan{relToParent=Just ComputedRelationship{}} _ ->
           Nothing
         Node ReadPlan{relToParent=Nothing} _ ->

src/PostgREST/Plan/ReadPlan.hs

@@ -1,8 +1,6 @@
-{-# LANGUAGE NamedFieldPuns #-}
 module PostgREST.Plan.ReadPlan
   ( ReadPlanTree
   , ReadPlan(..)
-  , fstFieldNames
   , JoinCondition(..)
   ) where
 
@@ -46,8 +44,3 @@ data ReadPlan = ReadPlan
   -- ^ used for aliasing
   }
   deriving (Eq)
-
--- First level FieldNames(e.g get a,b from /table?select=a,b,other(c,d))
-fstFieldNames :: ReadPlanTree -> [FieldName]
-fstFieldNames (Node ReadPlan{select} _) =
-  fst . (\(f, _, _) -> f) <$> select

src/PostgREST/SchemaCache/Relationship.hs

@@ -56,8 +56,8 @@ data Junction = Junction
   { junTable       :: QualifiedIdentifier
   , junConstraint1 :: FKConstraint
   , junConstraint2 :: FKConstraint
-  , junColumns1    :: [(FieldName, FieldName)]
-  , junColumns2    :: [(FieldName, FieldName)]
+  , junColsSource  :: [(FieldName, FieldName)]
+  , junColsTarget  :: [(FieldName, FieldName)]
   }
   deriving (Eq, Ord, Generic, JSON.ToJSON)