Fix splitByIndex diff

core/src/scalive/DiffBuilder.scala

@@ -41,19 +41,18 @@ object DiffBuilder:
       case Content.DynElementColl(dyn) => ???
       case Content.DynSplit(splitVar)  =>
         splitVar.render(trackUpdates) match
-          case Some((entries, keysCount)) =>
+          case Some((entries, keysCount, includeStatics)) =>
             val static =
-              entries.collectFirst { case (_, Some(el)) => el.static }.getOrElse(List.empty)
-            val includeStatic = !trackUpdates || keysCount == entries.count(_._2.isDefined)
+              if !trackUpdates || includeStatics then
+                entries.collectFirst { case (_, el) => el.static }.getOrElse(List.empty)
+              else List.empty
             List(
               Some(
                 Diff.Comprehension(
-                  static = if includeStatic then static else Seq.empty,
-                  entries = entries.map {
-                    case (key, Some(el)) =>
+                  static = static,
+                  entries = entries.map((key, el) =>
                     Diff.Dynamic(key.toString, build(Seq.empty, el.dynamicMods, trackUpdates))
-                    case (key, None) => Diff.Dynamic(key.toString, Diff.Deleted)
-                  },
+                  ),
                   count = keysCount
                 )
               )

core/src/scalive/Dyn.scala

@@ -99,10 +99,12 @@ private class SplitVar[I, O, Key](
   private val memoized: mutable.Map[Key, (Var[I], O)] =
     mutable.Map.empty
 
+  private var nonEmptySyncCount = 0
+
   private[scalive] def sync(): Unit =
     parent.sync()
     if parent.changed then
-      // We keep track of the key to set deleted ones to None
+      // We keep track of the keys to remove deleted ones afterwards
       val nextKeys = mutable.HashSet.empty[Key]
       parent.currentValue.foreach(input =>
         val entryKey = key(input)
@@ -122,16 +124,19 @@ private class SplitVar[I, O, Key](
         if !nextKeys.contains(k) then
           val _ = memoized.remove(k)
       )
+    if memoized.nonEmpty then nonEmptySyncCount += 1
 
   private[scalive] def render(trackUpdates: Boolean)
-    : Option[(changeList: List[(Key, Option[O])], keysCount: Int)] =
+    : Option[(changeList: List[(Int, O)], keysCount: Int, includeStatics: Boolean)] =
     if parent.changed || !trackUpdates then
       Some(
         (
-          memoized.collect {
-            case (k, (entryVar, output)) if !trackUpdates || entryVar.changed => (k, Some(output))
+          changeList = memoized.values.zipWithIndex.collect {
+            case ((entryVar, output), index) if !trackUpdates || entryVar.changed =>
+              (index, output)
           }.toList,
-          memoized.size
+          keysCount = memoized.size,
+          includeStatics = nonEmptySyncCount == 1
         )
       )
     else None

core/src/scalive/HtmlBuilder.scala

@@ -33,13 +33,11 @@ object HtmlBuilder:
           dyn.render(false).foreach(_.foreach(el => build(el.static, el.dynamicMods, strw)))
         case Content.DynElementColl(dyn) => ???
         case Content.DynSplit(splitVar)  =>
-          val (entries, _) = splitVar.render(false).getOrElse(List.empty -> 0)
-          val staticOpt    = entries.collectFirst { case (_, Some(el)) => el.static }
-          entries.foreach {
-            case (_, Some(entryEl)) =>
+          val (entries, _, _) = splitVar.render(false).getOrElse((List.empty, 0, true))
+          val staticOpt       = entries.collectFirst { case (_, el) => el.static }
+          entries.foreach((_, entryEl) =>
             build(staticOpt.getOrElse(Nil), entryEl.dynamicMods, strw)
-            case _ => ()
-          }
+          )
     strw.write(static.last)
 
 end HtmlBuilder

core/test/src/scalive/LiveViewSpec.scala

@@ -290,6 +290,48 @@ object LiveViewSpec extends TestSuite:
           )
         )
       }
+      test("diff add one to empty list") {
+        val model = Var(TestModel(items = List.empty))
+        val el    =
+          div(
+            ul(
+              model(_.items).splitByIndex((_, elem) =>
+                li(
+                  "Nom: ",
+                  elem(_.name),
+                  " Age: ",
+                  elem(_.age.toString)
+                )
+              )
+            )
+          )
+        el.syncAll()
+        el.setAllUnchanged()
+
+        model.update(_.copy(items = List(NestedModel("a", 20))))
+
+        assertEqualsDiff(
+          el,
+          Json.Obj(
+            "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("a"),
+                      "1" -> Json.Str("20")
+                    ),
+                    "kc" -> Json.Num(1)
+                  )
+                )
+          )
+        )
+      }
       test("diff with first item removed") {
         model.update(_.copy(items = initModel.items.tail))
         assertEqualsDiff(