Support non-id primary key joins with columns not declared as ForeignKey but of ParentId type

src/Database/Esqueleto/Internal/Sql.hs

@@ -522,7 +522,12 @@ unsafeSqlBinOpList op sep (ERawList f1) (ERawList f2) = ERaw Never f
                   zip b1 b2
                 , vals1 <> vals2 )
 unsafeSqlBinOpList op _ a@(ERaw _ _) b@(ERaw _ _) = unsafeSqlBinOp op a b
-unsafeSqlBinOpList _ _ _ _ = error "unsafeSqlBinOpList: must operate against another composite key"
+unsafeSqlBinOpList op sep (ERaw p1 f1) b@(ERawList _) = unsafeSqlBinOpList op sep a b
+  where a = ERawList $ \info -> let (b1, vals1) = f1 info
+                                in ([parensM p1  b1], vals1)
+unsafeSqlBinOpList op sep a@(ERawList _) (ERaw p2 f2) = unsafeSqlBinOpList op sep a b
+  where b = ERawList $ \info -> let (b2, vals2) = f2 info
+                                in ([parensM p2  b2], vals2)
 {-# INLINE unsafeSqlBinOpList #-}
 
 -- | (Internal) A raw SQL value.  The same warning from

test/Test.hs

@@ -71,6 +71,10 @@ share [mkPersist sqlSettings, mkMigrate "migrateAll"] [persistUpperCase|
     frontcoverNumber Int
     Foreign Frontcover fkfrontcover frontcoverNumber
     deriving Eq Show
+  Article2
+    title String
+    frontcoverId FrontcoverId
+    deriving Eq Show
   Point
     x Int
     y Int
@@ -979,7 +983,7 @@ main = do
             pPk `shouldBe` thePk
       -}
 
-      it "can join with a non-id primary key and return one entity" $
+      it "can join a ForeignKey with a non-id primary key and return one entity" $
         run $ do
           let fc = Frontcover number ""
               article = Article "Esqueleto supports composite pks!" number
@@ -995,7 +999,7 @@ main = do
             retFc `shouldBe` fc
             fcPk `shouldBe` thePk
 
-      it "can join with a non-id primary key and return both entities" $
+      it "can join a ForeignKey with a non-id primary key and return both entities" $
         run $ do
           let fc = Frontcover number ""
               article = Article "Esqueleto supports composite pks!" number
@@ -1012,6 +1016,22 @@ main = do
             retArt `shouldBe` article
             fcPk `shouldBe` thePk
             articleFkfrontcover retArt `shouldBe` thePk
+
+      it "can join with a non-id primary key and return one entity" $
+        run $ do
+          let fc = Frontcover number ""
+              article = Article2 "Esqueleto supports composite pks!" thePk
+              number = 101
+              Right thePk = keyFromValues [PersistInt64 $ fromIntegral number]
+          fcPk <- insert fc
+          insert_ article
+          [Entity _ retFc] <- select $
+            from $ \(a `InnerJoin` f) -> do
+              on (f^.FrontcoverId ==. a^.Article2FrontcoverId)
+              return f
+          liftIO $ do
+            retFc `shouldBe` fc
+            fcPk `shouldBe` thePk
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