handle inserting no data correctly

with "insert into [table] default values"

src/PgQuery.hs

@@ -165,9 +165,11 @@ placeholders :: String -> SqlRow -> String
 placeholders symbol = intercalate ", " . map (const symbol) . getRow
 
 insertClause :: Schema -> Text -> SqlRow -> QuotedSql
+insertClause schema table (SqlRow []) =
+  ("insert into %I.%I default values returning *", [toSql schema, toSql table])
 insertClause schema table row =
-    ("insert into %I.%I (" ++ placeholders "%I" row ++ ")",
-     map toSql $ cs schema : table : sqlRowColumns row)
+  ("insert into %I.%I (" ++ placeholders "%I" row ++ ")",
+  map toSql $ cs schema : table : sqlRowColumns row)
   <> (" values (" ++ placeholders "?" row ++ ") returning *", sqlRowValues row)
 
 

test/Unit/PgQuerySpec.hs

@@ -53,6 +53,12 @@ spec = around dbWithSchema $ do
           ("nullable_string", toSql ("a string"::String))]) conn
           `shouldThrow` \e -> seState e == "23502"
 
+      it "generates a default values query if no data is provided" $ \c -> do
+        r <- insert "1" "items" (SqlRow []) c
+        let [row] = toList r
+        quickALQuery c "select * from \"1\".items where id = ?" [snd row]
+          `shouldReturn` [[row]]
+
   let {user = "jdoe"; pass = "secret"; role = "test_default_role"}
   describe "addUser" $ do
     it "adds a correct user to the right table" $ \conn -> do