having followup transactions during observation makes weird observer …

…timings

Modules/Example Todolist/src/main/scala/todo/TaskData.scala

@@ -121,8 +121,9 @@ class TaskReferences(toggleAll: Event[dom.Event], storePrefix: String) {
     GlobalRegistry.publish(taskID, crdt)
     GlobalRegistry.unbuffer(taskID)
 
-    val taskData =
-      crdt.map(x => x.state.data.read.getOrElse(TaskData(desc = "LWW Empty")))
+    val taskData = Signal {
+      crdt.value.state.data.read.getOrElse(TaskData(desc = "LWW Empty"))
+    }
 
     val removeButton =
       Event.fromCallback(button(`class` := "destroy", onclick := Event.handle))

Modules/Reactives/shared/src/main/scala/reactives/core/Core.scala

@@ -166,6 +166,8 @@ trait Transaction[State[_]] {
 
   def observe(obs: Observation): Unit
 
+  def followup(obs: Observation): Unit = observe(obs)
+
   def initializer: Initializer[State]
 
   private[reactives] def discover(source: ReSource.of[State], sink: Derived.of[State]): Unit = {

Modules/Reactives/shared/src/main/scala/reactives/core/ScopeSearches.scala

@@ -59,7 +59,7 @@ object PlanTransactionScope {
   case class StaticInTransaction[State[_]](tx: Transaction[State], scheduler: Scheduler[State])
       extends PlanTransactionScope[State] {
     override def planTransaction(inintialWrites: ReSource.of[State]*)(admission: AdmissionTicket[State] => Unit): Unit =
-      tx.observe { () =>
+      tx.followup { () =>
         scheduler.forceNewTransaction(inintialWrites*)(admission)
       }
   }
@@ -68,7 +68,7 @@ object PlanTransactionScope {
       extends PlanTransactionScope[State] {
     override def planTransaction(inintialWrites: ReSource.of[State]*)(admission: AdmissionTicket[State] => Unit): Unit =
       dynamicScope.maybeTransaction match
-        case Some(tx) => tx.observe { () =>
+        case Some(tx) => tx.followup { () =>
             scheduler.forceNewTransaction(inintialWrites*)(admission)
           }
         case None =>

Modules/Reactives/shared/src/main/scala/reactives/scheduler/Twoversion.scala

@@ -171,6 +171,7 @@ trait Twoversion {
 
     val toCommit      = ListBuffer[ReSource]()
     val observers     = ListBuffer[Observation]()
+    val followups     = ListBuffer[Observation]()
     var commitStarted = false
 
     override def schedule(commitable: ReSource): Unit = { toCommit += commitable; () }
@@ -180,7 +181,17 @@ trait Twoversion {
         s"Added observation to transaction (${this}), but it is too late in its lifecycle. " +
         s"This may happen due to capturing a transaction reference such that it survives outside of its dynamic scope."
       )
-      observers += f; ()
+      observers += f
+      ()
+    }
+
+    override def followup(obs: Observation): Unit = {
+      if (commitStarted) throw new IllegalStateException(
+        s"Added observation to transaction (${this}), but it is too late in its lifecycle. " +
+        s"This may happen due to capturing a transaction reference such that it survives outside of its dynamic scope."
+      )
+      followups += obs
+      ()
     }
 
     override def commitPhase(): Unit = {
@@ -200,6 +211,12 @@ trait Twoversion {
       // we should probably aggregate all of the exceptions,
       // but this is not the place to invent exception aggregation
       if (failure != null) throw failure
+
+      followups.foreach { n =>
+        try n.execute()
+        catch { case NonFatal(e) => failure = e }
+      }
+      if (failure != null) throw failure
     }
 
     final def commitDependencyDiff(node: Derived, current: Set[ReSource])(updated: Set[ReSource]): Unit = {