server: fix MySQL connection pool settings getting swapped on parse

PR-URL: https://github.com/hasura/graphql-engine-mono/pull/6063
GitOrigin-RevId: 90f6f8485aa6a9d073edc56dcba5530f5cf787c4

server/graphql-engine.cabal

@@ -988,6 +988,7 @@ test-suite graphql-engine-tests
     Hasura.Backends.DataConnector.API.V0.TableSpec
     Hasura.Backends.MSSQL.ErrorSpec
     Hasura.Backends.MySQL.DataLoader.ExecuteTests
+    Hasura.Backends.MySQL.TypesSpec
     Hasura.Backends.Postgres.Execute.PrepareSpec
     Hasura.Backends.Postgres.RQLGenerator
     Hasura.Backends.Postgres.RQLGenerator.GenAnnSelectG

server/src-lib/Hasura/Backends/MySQL/Types/Instances.hs

@@ -199,8 +199,8 @@ instance Semigroup Top where
 instance J.FromJSON ConnPoolSettings where
   parseJSON = J.withObject "MySQL pool settings" $ \o ->
     ConnPoolSettings
-      <$> o J..:? "max_connections" J..!= _cscMaxConnections defaultConnPoolSettings
-      <*> o J..:? "idle_timeout" J..!= _cscIdleTimeout defaultConnPoolSettings
+      <$> o J..:? "idle_timeout" J..!= _cscIdleTimeout defaultConnPoolSettings
+      <*> o J..:? "max_connections" J..!= _cscMaxConnections defaultConnPoolSettings
 
 $(J.deriveToJSON hasuraJSON ''ConnPoolSettings)
 

server/src-test/Hasura/Backends/MySQL/TypesSpec.hs

@@ -0,0 +1,30 @@
+{-# LANGUAGE QuasiQuotes #-}
+
+module Hasura.Backends.MySQL.TypesSpec (spec) where
+
+import Data.Aeson (parseJSON, toJSON)
+import Data.Aeson.QQ (aesonQQ)
+import Data.Aeson.Types (parseEither)
+import Hasura.Backends.MySQL.Types (ConnPoolSettings (..))
+import Hasura.Prelude
+import Test.Hspec
+
+spec :: Spec
+spec = do
+  describe "MySQL" do
+    describe "ConnPoolSettings" do
+      it "should parse idle timeout and max connections" do
+        let input =
+              [aesonQQ|
+                { "idle_timeout": 100,
+                  "max_connections": 10
+                }
+              |]
+        let decoded = parseEither parseJSON input
+        let expected = ConnPoolSettings {_cscIdleTimeout = 100, _cscMaxConnections = 10}
+        decoded `shouldBe` Right expected
+
+      it "should round-trip" do
+        let expected = ConnPoolSettings {_cscIdleTimeout = 100, _cscMaxConnections = 10}
+        let actual = parseEither parseJSON $ toJSON expected
+        actual `shouldBe` Right expected