Fix splitBy ordering, properly this time

scalive/core/src/scalive/Dyn.scala

@@ -37,7 +37,7 @@ sealed trait Dyn[T]:
   private[scalive] def callOnEveryChild(f: T => Unit): Unit
 
 extension [T](parent: Dyn[List[T]])
-  def splitBy[Key: Ordering](key: T => Key)(project: (Key, Dyn[T]) => HtmlElement): Mod =
+  def splitBy[Key](key: T => Key)(project: (Key, Dyn[T]) => HtmlElement): Mod =
     Mod.Content.DynSplit(
       new SplitVar(
         parent,
@@ -90,13 +90,15 @@ private class DerivedVar[I, O] private[scalive] (parent: Var[I], f: I => O) exte
 
   private[scalive] def callOnEveryChild(f: O => Unit): Unit = f(currentValue)
 
-private class SplitVar[I, O, Key: Ordering](
+private class SplitVar[I, O, Key](
   parent: Dyn[List[I]],
   key: I => Key,
   project: (Key, Dyn[I]) => O):
 
   private val memoized: mutable.Map[Key, (Var[I], O)] =
-    mutable.TreeMap.empty
+    mutable.Map.empty
+
+  private var orderedKeys = List.empty[Key]
 
   private var previousKeysToIndex: Map[Key, Int] = Map.empty
 
@@ -105,9 +107,10 @@ private class SplitVar[I, O, Key: Ordering](
   private[scalive] def sync(): Unit =
     parent.sync()
     if parent.changed then
-      previousKeysToIndex = memoized.keys.zipWithIndex.toMap
+      previousKeysToIndex = orderedKeys.zipWithIndex.toMap
       // We keep track of the keys to remove deleted ones afterwards
       val nextKeys = mutable.HashSet.empty[Key]
+      orderedKeys = parent.currentValue.map(key)
       parent.currentValue.foreach(input =>
         val entryKey = key(input)
         nextKeys += entryKey
@@ -138,7 +141,8 @@ private class SplitVar[I, O, Key: Ordering](
     if parent.changed || !trackUpdates then
       Some(
         (
-          changeList = memoized.zipWithIndex
+          changeList = orderedKeys
+            .map(k => (k, memoized(k))).zipWithIndex
             .map { case ((key, (entryVar, output)), index) =>
               (index, previousKeysToIndex.get(key).filterNot(_ == index), entryVar, output)
             }

scalive/core/test/src/scalive/LiveViewSpec.scala

@@ -550,5 +550,91 @@ object LiveViewSpec extends TestSuite:
       }
     }
 
+    test("splitBy ordering") {
+      val initModel = TestModel(
+        items = List(
+          NestedModel("c", 20),
+          NestedModel("a", 10),
+          NestedModel("b", 15)
+        )
+      )
+      val model = Var(initModel)
+      val el    =
+        div(
+          ul(
+            model(_.items).splitBy(_.name)((_, elem) =>
+              li(
+                "Nom: ",
+                elem(_.name),
+                " Age: ",
+                elem(_.age.toString)
+              )
+            )
+          )
+        )
+
+      el.syncAll()
+      el.setAllUnchanged()
+
+      test("init should preserve list order") {
+        assertEqualsDiff(
+          el,
+          Json
+            .Obj(
+              "s" -> Json.Arr(Json.Str("<div><ul>"), Json.Str("</ul></div>")),
+              "0" -> Json.Obj(
+                "s" -> Json.Arr(
+                  Json.Str("<li>Nom: "),
+                  Json.Str(" Age: "),
+                  Json.Str("</li>")
+                ),
+                "k" -> Json.Obj(
+                  "0" -> Json.Obj(
+                    "0" -> Json.Str("c"),
+                    "1" -> Json.Str("20")
+                  ),
+                  "1" -> Json.Obj(
+                    "0" -> Json.Str("a"),
+                    "1" -> Json.Str("10")
+                  ),
+                  "2" -> Json.Obj(
+                    "0" -> Json.Str("b"),
+                    "1" -> Json.Str("15")
+                  ),
+                  "kc" -> Json.Num(3)
+                )
+              )
+            ),
+          trackChanges = false
+        )
+      }
+
+      test("reorder items") {
+        model.update(
+          _.copy(items =
+            List(
+              NestedModel("b", 15), // Should be at index 0
+              NestedModel("a", 10), // Should be at index 1
+              NestedModel("c", 20)  // Should be at index 2
+            )
+          )
+        )
+        assertEqualsDiff(
+          el,
+          Json.Obj(
+            "0" ->
+              Json
+                .Obj(
+                  "k" -> Json.Obj(
+                    "0"  -> Json.Num(2),
+                    "2"  -> Json.Num(0),
+                    "kc" -> Json.Num(3)
+                  )
+                )
+          )
+        )
+      }
+    }
+
   }
 end LiveViewSpec