fix: 🐛 index of actions will be changed in another coroutine

core/src/main/kotlin/tw/xcc/gumtree/editscript/SimplifiedEditScriptGenerator.kt

@@ -14,6 +14,7 @@ import tw.xcc.gumtree.model.operations.SingleDeleteAction
 import tw.xcc.gumtree.model.operations.SingleInsertAction
 import tw.xcc.gumtree.model.operations.TreeDeleteAction
 import tw.xcc.gumtree.model.operations.TreeInsertAction
+import java.util.Optional
 
 /**
  * A second-stage edit script generator that simplifies the edit script generated by the [ChawatheScriptGenerator].
@@ -40,10 +41,10 @@ class SimplifiedEditScriptGenerator(
 
     /**
      * Replace single tree [Action] with another tree [Action]
-     * if the node and all of its descendents are also in the [actions] list.
+     * if the node and all of its descendents are also in the [flatActions] list.
      * */
     private suspend inline fun <T : Action, N : Action> simplifyWith(
-        actions: MutableList<Action>,
+        flatActions: MutableList<Optional<Action>>,
         nodeToIndexedSingleActions: Map<GumTree, Pair<Int, T>>,
         crossinline createTreeActionFrom: (origin: T) -> N
     ) = coroutineScope {
@@ -54,26 +55,28 @@ class SimplifiedEditScriptGenerator(
 
             if (nodeAsKeys.contains(nodeParent) && nodeAsKeys.containsAll(descendentsOf(nodeParent))) {
                 lock.withLock {
-                    actions.removeAt(indexInOriginActions)
+                    flatActions[indexInOriginActions] = Optional.empty()
                 }
             } else if (node.childCount() > 0 && nodeAsKeys.containsAll(descendentsOf(node))) {
                 val treeAction = createTreeActionFrom(originAction)
                 lock.withLock {
-                    actions.add(indexInOriginActions, treeAction)
-                    actions.removeAt(indexInOriginActions + 1)
+                    flatActions[indexInOriginActions] = Optional.of(treeAction)
                 }
             }
         }
     }
 
     override suspend fun generateActions(): List<Action> =
         coroutineScope {
-            val actions = baseGenerator.generateActions().toMutableList()
+            val actions =
+                baseGenerator.generateActions()
+                    .map { Optional.of(it) }
+                    .toMutableList()
 
             val simplifiableActions =
                 actions
                     .flatMapIndexed { originIdx, action ->
-                        when (action) {
+                        when (action.get()) {
                             is SingleInsertAction -> listOf(originIdx to action)
                             is SingleDeleteAction -> listOf(originIdx to action)
                             else -> emptyList()
@@ -110,6 +113,6 @@ class SimplifiedEditScriptGenerator(
                 }
 
             listOf(insertionSimplifyJob, deletionSimplifyJob).joinAll()
-            return@coroutineScope actions
+            return@coroutineScope actions.filter { it.isPresent }.map { it.get() }
         }
 }