fix: clear references to a task key after deleting a task

A small helper function which iterates through `workflow.tasks` and deletes references to a given task key. It's called after deleting a task, so that other tasks no longer link to the deleted task.

app/pages/lab/helpers/removeTaskKeyFromWorkflow.js

@@ -0,0 +1,14 @@
+export default function removeTaskKeyFromWorkflow(workflow, taskKey) {
+    const changes = {};
+    Object.entries(workflow.tasks).forEach(([key, task]) => {
+      if (task.next === taskKey) {
+        changes[`tasks.${key}.next`] = '';
+      }
+      task.answers?.forEach((answer, index) => {
+        if (answer.next === taskKey) {
+          changes[`tasks.${key}.answers.${index}.next`] = '';
+        }
+      });
+    });
+    return workflow.update(changes);
+}

app/pages/lab/helpers/removeTaskKeyFromWorkflow.spec.js

@@ -0,0 +1,43 @@
+import { expect } from 'chai';
+import sinon from 'sinon';
+import removeTaskKeyFromWorkflow from './removeTaskKeyFromWorkflow.js';
+
+describe('removeTaskKeyFromWorkflow', function () {
+  let workflow;
+
+  beforeEach(function () {
+    workflow = {
+      tasks: {
+        'T1': {
+          type: 'single',
+          answers: [
+            { label: 'Yes', next: 'T3' },
+            { label: 'No', next: 'T2' }
+          ]
+        },
+        'T2': {
+          type: 'multiple',
+          next: 'T3',
+          answers: [
+            { label: 'Blue' },
+            { label: 'Green' }
+          ]
+        },
+        'T3': {
+          type: 'text',
+          next: ''
+        }
+      },
+      update: sinon.stub(),
+      save: sinon.stub()
+    };
+  });
+
+  it('should delete the selected key from each task', function () {
+    removeTaskKeyFromWorkflow(workflow, 'T3');
+    expect(workflow.update).to.have.been.calledWith({
+      'tasks.T1.answers.0.next': '',
+      'tasks.T2.next': ''
+    });
+  });
+});

app/pages/lab/workflow.jsx

@@ -21,6 +21,7 @@ import Tutorials from './workflow-components/tutorials.jsx';
 import TaskOptions from './workflow-components/task-options.jsx';
 import TaskPicker from './workflow-components/task-picker.jsx';
 import TaskEditor from './workflow-components/task-editor.jsx';
+import removeTaskFromWorkflow from './helpers/removeTaskKeyFromWorkflow.js';
 
 const DEMO_SUBJECT_SET_ID = process.env.NODE_ENV === 'production'
 ? '6' // Cats
@@ -807,8 +808,9 @@ class EditWorkflowPage extends Component {
         changes[`tasks.${taskKey}`] = undefined;
         this.props.workflow.update(changes);
       }
+      removeTaskFromWorkflow(this.props.workflow, taskKey);
 
-      return this.updateFirstTask();
+      return this.updateFirstTask().save();
     }
   }
 }