Fixed jump to next discussion button not working

Fixes the jump to next discusion which could be caused by
the discussion not returning correctly

Closes https://gitlab.com/gitlab-org/gitlab/-/issues/232802

app/assets/javascripts/merge_request_tabs.js

@@ -166,8 +166,6 @@ export default class MergeRequestTabs {
         if (this.setUrl) {
           this.setCurrentAction(action);
         }
-
-        this.eventHub.$emit('MergeRequestTabChange', this.getCurrentAction());
       }
     }
   }
@@ -251,6 +249,8 @@ export default class MergeRequestTabs {
         }
       }
     }
+
+    this.eventHub.$emit('MergeRequestTabChange', action);
   }
 
   scrollToElement(container) {

app/assets/javascripts/notes/mixins/discussion_navigation.js

@@ -78,7 +78,7 @@ function handleDiscussionJump(self, fn, discussionId = self.currentDiscussionId)
   const isDiffView = window.mrTabs.currentAction === 'diffs';
   const targetId = fn(discussionId, isDiffView);
   const discussion = self.getDiscussion(targetId);
-  const discussionFilePath = discussion.diff_file?.file_path;
+  const discussionFilePath = discussion?.diff_file?.file_path;
 
   if (discussionFilePath) {
     self.scrollToFile(discussionFilePath);

app/assets/javascripts/notes/stores/getters.js

@@ -194,7 +194,9 @@ export const findUnresolvedDiscussionIdNeighbor = (state, getters) => ({
   diffOrder,
   step,
 }) => {
-  const ids = getters.unresolvedDiscussionsIdsOrdered(diffOrder);
+  const diffIds = getters.unresolvedDiscussionsIdsOrdered(diffOrder);
+  const dateIds = getters.unresolvedDiscussionsIdsOrdered(false);
+  const ids = diffIds.length ? diffIds : dateIds;
   const index = ids.indexOf(discussionId) + step;
 
   if (index < 0 && step < 0) {

spec/features/merge_request/user_jumps_to_discussion_spec.rb

+# frozen_string_literal: true
+
+require 'spec_helper'
+
+RSpec.describe 'User jumps to the next unresolved discussion', :js do
+  let(:project) { create(:project, :repository) }
+  let(:merge_request) do
+    create(:merge_request_with_diffs, source_project: project, target_project: project, source_branch: 'merge-test')
+  end
+
+  let(:user) { create(:user) }
+
+  before do
+    create(:discussion_note, noteable: merge_request, project: project, author: user)
+
+    project.add_maintainer(user)
+    sign_in(user)
+
+    visit(diffs_project_merge_request_path(project, merge_request))
+
+    wait_for_requests
+  end
+
+  it 'jumps to overview tab' do
+    find('.discussion-next-btn').click
+
+    expect(page).to have_css('.notes-tab.active')
+  end
+end