Merge branch '15081-wrong-login-tab-ldap-frontend' into 'master'

Fixed Wrong Tab Selected When Loggin Fails And Multiple Login Tabs Exists

## What does this MR do?
Fixes issue: 15081 Wrong Tab Selected When Loggin Fails And Multiple Login Tabs Exists
This is done by saving into a cookie when the active tab changes and by always selecting that tab when the page is loaded.
## Are there points in the code the reviewer needs to double check?
No
## Why was this MR needed?
In order to fix the issue: 15081
## Screenshots (if relevant)

## Does this MR meet the acceptance criteria?

- [x] [Changelog entry](https://docs.gitlab.com/ce/development/changelog.html) added
- [ ] [Documentation created/updated](https://gitlab.com/gitlab-org/gitlab-ce/blob/master/doc/development/doc_styleguide.md)
- [ ] API support added
- Tests
  - [x] Added for this feature/bug
  - [x] All builds are passing
- [x] Conform by the [merge request performance guides](http://docs.gitlab.com/ce/development/merge_request_performance_guidelines.html)
- [x] Conform by the [style guides](https://gitlab.com/gitlab-org/gitlab-ce/blob/master/CONTRIBUTING.md#style-guides)
- [x] Branch has no merge conflicts with `master` (if it does - rebase it please)
- [x] [Squashed related commits together](https://git-scm.com/book/en/Git-Tools-Rewriting-History#Squashing-Commits)

## What are the relevant issue numbers?


Closes #15081

See merge request !7314

.eslintrc

@@ -8,7 +8,8 @@
   "globals": {
     "_": false,
     "gl": false,
-    "gon": false
+    "gon": false,
+    "localStorage": false
   },
   "plugins": [
     "filenames"

app/assets/javascripts/dispatcher.js.es6

@@ -24,6 +24,7 @@
       switch (page) {
         case 'sessions:new':
           new UsernameValidator();
+          new ActiveTabMemoizer();
           break;
         case 'projects:boards:show':
         case 'projects:boards:index':

app/assets/javascripts/signin_tabs_memoizer.js.es6

+/* eslint no-param-reassign: ["error", { "props": false }]*/
+/* eslint no-new: "off" */
+((global) => {
+  /**
+   * Memorize the last selected tab after reloading a page.
+   * Does that setting the current selected tab in the localStorage
+   */
+  class ActiveTabMemoizer {
+    constructor({ currentTabKey = 'current_signin_tab', tabSelector = 'ul.nav-tabs' } = {}) {
+      this.currentTabKey = currentTabKey;
+      this.tabSelector = tabSelector;
+      this.bootstrap();
+    }
+
+    bootstrap() {
+      const tabs = document.querySelectorAll(this.tabSelector);
+      if (tabs.length > 0) {
+        tabs[0].addEventListener('click', (e) => {
+          if (e.target && e.target.nodeName === 'A') {
+            const anchorName = e.target.getAttribute('href');
+            this.saveData(anchorName);
+          }
+        });
+      }
+
+      this.showTab();
+    }
+
+    showTab() {
+      const anchorName = this.readData();
+      if (anchorName) {
+        const tab = document.querySelector(`${this.tabSelector} a[href="${anchorName}"]`);
+        if (tab) {
+          tab.click();
+        }
+      }
+    }
+
+    saveData(val) {
+      localStorage.setItem(this.currentTabKey, val);
+    }
+
+    readData() {
+      return localStorage.getItem(this.currentTabKey);
+    }
+  }
+
+  global.ActiveTabMemoizer = ActiveTabMemoizer;
+})(window);

app/views/devise/sessions/new.html.haml

 - page_title "Sign in"
+
 %div
   - if form_based_providers.any?
     = render 'devise/shared/tabs_ldap'

changelogs/unreleased/15081-wrong-login-tab-ldap-frontend.yml

+---
+title: Fix wrong tab selected when loggin fails and multiple login tabs exists
+merge_request: 7314
+author: Jacopo Beschi @jacopo-beschi 

spec/javascripts/fixtures/signin_tabs.html.haml

+%ul.nav-tabs
+  %li
+    %a.active{ id: 'standard', href: '#standard'} Standard
+  %li
+    %a{ id: 'ldap', href: '#ldap'} Ldap

spec/javascripts/signin_tabs_memoizer_spec.js.es6

+/*= require signin_tabs_memoizer */
+
+((global) => {
+  describe('SigninTabsMemoizer', () => {
+    const fixtureTemplate = 'signin_tabs.html';
+    const tabSelector = 'ul.nav-tabs';
+    const currentTabKey = 'current_signin_tab';
+    let memo;
+
+    function createMemoizer() {
+      memo = new global.ActiveTabMemoizer({
+        currentTabKey,
+        tabSelector,
+      });
+      return memo;
+    }
+
+    fixture.preload(fixtureTemplate);
+
+    beforeEach(() => {
+      fixture.load(fixtureTemplate);
+    });
+
+    it('does nothing if no tab was previously selected', () => {
+      createMemoizer();
+
+      expect(document.querySelector('li a.active').getAttribute('id')).toEqual('standard');
+    });
+
+    it('shows last selected tab on boot', () => {
+      createMemoizer().saveData('#ldap');
+      const fakeTab = {
+        click: () => {},
+      };
+      spyOn(document, 'querySelector').and.returnValue(fakeTab);
+      spyOn(fakeTab, 'click');
+
+      memo.bootstrap();
+
+      // verify that triggers click on the last selected tab
+      expect(document.querySelector).toHaveBeenCalledWith(`${tabSelector} a[href="#ldap"]`);
+      expect(fakeTab.click).toHaveBeenCalled();
+    });
+
+    it('saves last selected tab on change', () => {
+      createMemoizer();
+
+      document.getElementById('standard').click();
+
+      expect(memo.readData()).toEqual('#standard');
+    });
+  });
+})(window);