From 88d540eb8e0b659c9621cc5c365bd626a000c1d7 Mon Sep 17 00:00:00 2001
From: =?UTF-8?q?Mateusz=20Burzy=C5=84ski?= <mateuszburzynski@gmail.com>
Date: Sat, 25 Jun 2022 10:00:44 +0200
Subject: [PATCH] Fixed an issue with targeted ancestor reentrancy (#3424)

---
 .changeset/unlucky-sloths-tell.md  |  5 +++++
 packages/core/src/StateNode.ts     | 21 +++++++++++----------
 packages/core/test/actions.test.ts | 28 ++++++++++++++++++++++++++++
 3 files changed, 44 insertions(+), 10 deletions(-)
 create mode 100644 .changeset/unlucky-sloths-tell.md

diff --git a/.changeset/unlucky-sloths-tell.md b/.changeset/unlucky-sloths-tell.md
new file mode 100644
index 0000000000..c2f71d04ee
--- /dev/null
+++ b/.changeset/unlucky-sloths-tell.md
@@ -0,0 +1,5 @@
+---
+'xstate': patch
+---
+
+Fixed an issue with targeted ancestors not being correctly reentered during external transitions.
diff --git a/packages/core/src/StateNode.ts b/packages/core/src/StateNode.ts
index 6cd9237b56..3377822d0c 100644
--- a/packages/core/src/StateNode.ts
+++ b/packages/core/src/StateNode.ts
@@ -956,8 +956,8 @@ class StateNode<
     const reentryNodes: StateNode<any, any, any, any, any>[] = [];
 
     if (!isInternal) {
-      allNextStateNodes.forEach((n1) => {
-        reentryNodes.push(...this.getExternalReentryNodes(n1));
+      nextStateNodes.forEach((targetNode) => {
+        reentryNodes.push(...this.getExternalReentryNodes(targetNode));
       });
     }
 
@@ -972,23 +972,24 @@ class StateNode<
   }
 
   private getExternalReentryNodes(
-    childStateNode: StateNode<TContext, any, TEvent, any, any, any>
+    targetNode: StateNode<TContext, any, TEvent, any, any, any>
   ): Array<StateNode<TContext, any, TEvent, any, any, any>> {
     const nodes: Array<StateNode<TContext, any, TEvent, any, any, any>> = [];
-    let marker:
-      | StateNode<TContext, any, TEvent, any, any, any>
-      | undefined = childStateNode;
+    let [marker, possibleAncestor]: [
+      StateNode<TContext, any, TEvent, any, any, any> | undefined,
+      StateNode<TContext, any, TEvent, any, any, any>
+    ] = targetNode.order > this.order ? [targetNode, this] : [this, targetNode];
 
-    while (marker && marker !== this) {
+    while (marker && marker !== possibleAncestor) {
       nodes.push(marker);
       marker = marker.parent;
     }
-    if (marker !== this) {
-      // we never got to `this`, therefore the `childStateNode` "escapes" it
+    if (marker !== possibleAncestor) {
+      // we never got to `possibleAncestor`, therefore the initial `marker` "escapes" it
       // it's in a different part of the tree so no states will be reentered for such an external transition
       return [];
     }
-    nodes.push(this);
+    nodes.push(possibleAncestor);
     return nodes;
   }
 
diff --git a/packages/core/test/actions.test.ts b/packages/core/test/actions.test.ts
index ca28ba1ac3..c7528c6a5a 100644
--- a/packages/core/test/actions.test.ts
+++ b/packages/core/test/actions.test.ts
@@ -383,6 +383,34 @@ describe('entry/exit actions', () => {
       expect(stateA.actions.map((action) => action.type)).toEqual(['D2 Exit']);
     });
 
+    it("should reenter targeted ancestor (as it's a descendant of the transition domain)", () => {
+      const actual: string[] = [];
+      const machine = createMachine({
+        initial: 'loaded',
+        states: {
+          loaded: {
+            id: 'loaded',
+            entry: () => actual.push('loaded entry'),
+            initial: 'idle',
+            states: {
+              idle: {
+                on: {
+                  UPDATE: '#loaded'
+                }
+              }
+            }
+          }
+        }
+      });
+
+      const service = interpret(machine).start();
+
+      actual.length = 0;
+      service.send('UPDATE');
+
+      expect(actual).toEqual(['loaded entry']);
+    });
+
     describe('should ignore same-parent state actions (sparse)', () => {
       const fooBar = {
         initial: 'foo',