Remove regex implementation and adjust for comments

Remove conditional for calling updateDetailsState

Add guard for different node lengths in issue_description

Explicilty set open asttribute to true to avoid possible issues

app/assets/javascripts/issue_show/stores/index.js

+import _ from 'underscore';
 import { convertObjectPropsToCamelCase } from '~/lib/utils/common_utils';
+import updateDescription from '../utils/update_description';
 
 export default class Store {
   constructor(initialState) {
@@ -19,8 +21,15 @@ export default class Store {
     }
 
     Object.assign(this.state, convertObjectPropsToCamelCase(data));
+    // find if there is an open details node inside of the issue description.
+    const descriptionSection = document.body.querySelector(
+      '.detail-page-description.content-block',
+    );
+    const details =
+      !_.isNull(descriptionSection) && descriptionSection.getElementsByTagName('details');
+
+    this.state.descriptionHtml = updateDescription(data.description, details);
     this.state.titleHtml = data.title;
-    this.state.descriptionHtml = data.description;
     this.state.lock_version = data.lock_version;
   }
 

app/assets/javascripts/issue_show/utils/update_description.js

+import _ from 'underscore';
+
+/**
+ * Function that replaces the open attribute for the <details> element.
+ *
+ * @param {String} descriptionHtml - The html string passed back from the server as a result of polling
+ * @param {Array} details - All detail nodes inside of the issue description.
+ */
+
+const updateDescription = (descriptionHtml = '', details) => {
+  let detailNodes = details;
+
+  if (_.isEmpty(details)) {
+    detailNodes = [];
+  }
+
+  const placeholder = document.createElement('div');
+  placeholder.innerHTML = descriptionHtml;
+
+  const newDetails = placeholder.getElementsByTagName('details');
+
+  if (newDetails.length !== detailNodes.length) {
+    return descriptionHtml;
+  }
+
+  Array.from(newDetails).forEach((el, i) => {
+    /*
+     * <details> has an open attribute that can have a value, "", "true", "false"
+     * and will show the dropdown, which is why we are setting the attribute
+     * explicitly to true.
+     */
+    if (detailNodes[i].open) el.setAttribute('open', true);
+  });
+
+  return placeholder.innerHTML;
+};
+
+export default updateDescription;

changelogs/unreleased/61933-toggling-a-task-inside-a-collapsible-section-collapses-all-sections.yml

+---
+title: When user toggles task list item, keep details open until user closes the details
+  manually
+merge_request: 16153
+author:
+type: fixed

spec/frontend/issue_show/store_spec.js

+import Store from '~/issue_show/stores';
+import updateDescription from '~/issue_show/utils/update_description';
+
+jest.mock('~/issue_show/utils/update_description');
+
+describe('Store', () => {
+  let store;
+
+  beforeEach(() => {
+    store = new Store({
+      descriptionHtml: '<p>This is a description</p>',
+    });
+  });
+
+  describe('updateState', () => {
+    beforeEach(() => {
+      document.body.innerHTML = `
+            <div class="detail-page-description content-block">
+              <details open>
+                <summary>One</summary>
+              </details>
+              <details>
+                <summary>Two</summary>
+              </details>
+            </div>
+          `;
+    });
+
+    afterEach(() => {
+      document.getElementsByTagName('html')[0].innerHTML = '';
+    });
+
+    it('calls updateDetailsState', () => {
+      store.updateState({ description: '' });
+
+      expect(updateDescription).toHaveBeenCalledTimes(1);
+    });
+  });
+});

spec/frontend/issue_show/utils/update_description_spec.js

+import updateDescription from '~/issue_show/utils/update_description';
+
+describe('updateDescription', () => {
+  it('returns the correct value to be set as descriptionHtml', () => {
+    const actual = updateDescription(
+      '<details><summary>One</summary></details><details><summary>Two</summary></details>',
+      [{ open: true }, { open: false }], // mocking NodeList from the dom.
+    );
+
+    expect(actual).toEqual(
+      '<details open="true"><summary>One</summary></details><details><summary>Two</summary></details>',
+    );
+  });
+
+  describe('when description details returned from api is different then whats currently on the dom', () => {
+    it('returns the description from the api', () => {
+      const dataDescription = '<details><summary>One</summary></details>';
+
+      const actual = updateDescription(dataDescription, []);
+
+      expect(actual).toEqual(dataDescription);
+    });
+  });
+});

spec/javascripts/issue_show/components/app_spec.js

@@ -23,6 +23,14 @@ describe('Issuable output', () => {
   beforeEach(done => {
     setFixtures(`
       <div>
+        <div class="detail-page-description content-block">
+        <details open>
+          <summary>One</summary>
+        </details>
+        <details>
+          <summary>Two</summary>
+        </details>
+      </div>
         <div class="flash-container"></div>
         <span id="task_status"></span>
       </div>