From a1af7a775fed964d22d0760824c78601072b2b11 Mon Sep 17 00:00:00 2001
From: Isaries <leolove3very@gmail.com>
Date: Thu, 8 Oct 2026 14:37:13 +0800
Subject: [PATCH] fix(ProjectService): Empty lesson that transitions to itself
 overflows the stack

getLessonPaths() followed an empty lesson's transitions without checking
the path so far, so a lesson that transitions to itself recursed until
the stack overflowed. Parsing runs whenever a unit is opened for
authoring or preview, so one bad transition made the whole unit
unopenable, including the authoring view needed to repair it. Steps
already end the path on a loop; do the same for empty lessons.
---
 src/app/services/projectService.spec.ts     | 19 +++++++++++++++++++
 src/assets/wise5/services/projectService.ts |  4 ++++
 2 files changed, 23 insertions(+)

diff --git a/src/app/services/projectService.spec.ts b/src/app/services/projectService.spec.ts
index 9083c3302b0..ce46fc48886 100644
--- a/src/app/services/projectService.spec.ts
+++ b/src/app/services/projectService.spec.ts
@@ -354,6 +354,25 @@ function getAllPaths() {
       expect(allPaths2.length).toEqual(1);
       expect(allPaths2[0]).toEqual(['node5', 'node6', 'node7', 'node8']);
     });
+    it('should end the path at an empty lesson that transitions to itself', () => {
+      const project = copy(twoStepsProjectJSON);
+      project.nodes.find((node) => node.id === 'group0').ids.push('group3');
+      project.nodes.find((node) => node.id === 'group1').transitionLogic = {
+        transitions: [{ to: 'group3' }]
+      };
+      project.nodes.push({
+        id: 'group3',
+        type: 'group',
+        title: 'Empty Lesson',
+        startId: '',
+        ids: [],
+        transitionLogic: { transitions: [{ to: 'group3' }] }
+      });
+      service.setProject(project);
+      expect(service.getAllPaths([], service.getStartNodeId())).toEqual([
+        ['node1', 'node2', 'group3']
+      ]);
+    });
   });
 }
 
diff --git a/src/assets/wise5/services/projectService.ts b/src/assets/wise5/services/projectService.ts
index 2470e3fb0c8..0875809b4bb 100644
--- a/src/assets/wise5/services/projectService.ts
+++ b/src/assets/wise5/services/projectService.ts
@@ -1039,6 +1039,10 @@ export class ProjectService {
       const transitions = this.getTransitionsByFromNodeId(groupNode.id);
       if (transitions.length > 0) {
         for (const transition of transitions) {
+          if (pathSoFar.includes(transition.to)) {
+            allPaths.push([groupId]);
+            continue;
+          }
           const allPathsFromToNode = this.getAllPaths(pathSoFar, transition.to, includeGroups);
           for (const tempPath of allPathsFromToNode) {
             tempPath.unshift(groupId);