Add shift-tab keyboard support for dialogs (modal & Offcanvas components) (#33865)

* consolidate dialog focus trap logic

* add shift-tab support to focustrap

* remove redundant null check of trap element

Co-authored-by: GeoSot <geo.sotis@gmail.com>

* remove area support forom focusableChildren

* fix no expectations warning in focustrap tests

Co-authored-by: GeoSot <geo.sotis@gmail.com>
Co-authored-by: XhmikosR <xhmikosr@gmail.com>

js/tests/unit/util/focustrap.spec.js

@@ -0,0 +1,210 @@
+import FocusTrap from '../../../src/util/focustrap'
+import EventHandler from '../../../src/dom/event-handler'
+import SelectorEngine from '../../../src/dom/selector-engine'
+import { clearFixture, getFixture, createEvent } from '../../helpers/fixture'
+
+describe('FocusTrap', () => {
+  let fixtureEl
+
+  beforeAll(() => {
+    fixtureEl = getFixture()
+  })
+
+  afterEach(() => {
+    clearFixture()
+  })
+
+  describe('activate', () => {
+    it('should autofocus itself by default', () => {
+      fixtureEl.innerHTML = '<div id="focustrap" tabindex="-1"></div>'
+
+      const trapElement = fixtureEl.querySelector('div')
+
+      spyOn(trapElement, 'focus')
+
+      const focustrap = new FocusTrap({ trapElement })
+      focustrap.activate()
+
+      expect(trapElement.focus).toHaveBeenCalled()
+    })
+
+    it('if configured not to autofocus, should not autofocus itself', () => {
+      fixtureEl.innerHTML = '<div id="focustrap" tabindex="-1"></div>'
+
+      const trapElement = fixtureEl.querySelector('div')
+
+      spyOn(trapElement, 'focus')
+
+      const focustrap = new FocusTrap({ trapElement, autofocus: false })
+      focustrap.activate()
+
+      expect(trapElement.focus).not.toHaveBeenCalled()
+    })
+
+    it('should force focus inside focus trap if it can', done => {
+      fixtureEl.innerHTML = [
+        '<a href="#" id="outside">outside</a>',
+        '<div id="focustrap" tabindex="-1">',
+        '   <a href="#" id="inside">inside</a>',
+        '</div>'
+      ].join('')
+
+      const trapElement = fixtureEl.querySelector('div')
+      const focustrap = new FocusTrap({ trapElement })
+      focustrap.activate()
+
+      const inside = document.getElementById('inside')
+
+      const focusInListener = () => {
+        expect(inside.focus).toHaveBeenCalled()
+        document.removeEventListener('focusin', focusInListener)
+        done()
+      }
+
+      spyOn(inside, 'focus')
+      spyOn(SelectorEngine, 'focusableChildren').and.callFake(() => [inside])
+
+      document.addEventListener('focusin', focusInListener)
+
+      const focusInEvent = createEvent('focusin', { bubbles: true })
+      Object.defineProperty(focusInEvent, 'target', {
+        value: document.getElementById('outside')
+      })
+
+      document.dispatchEvent(focusInEvent)
+    })
+
+    it('should wrap focus around foward on tab', done => {
+      fixtureEl.innerHTML = [
+        '<a href="#" id="outside">outside</a>',
+        '<div id="focustrap" tabindex="-1">',
+        '   <a href="#" id="first">first</a>',
+        '   <a href="#" id="inside">inside</a>',
+        '   <a href="#" id="last">last</a>',
+        '</div>'
+      ].join('')
+
+      const trapElement = fixtureEl.querySelector('div')
+      const focustrap = new FocusTrap({ trapElement })
+      focustrap.activate()
+
+      const first = document.getElementById('first')
+      const inside = document.getElementById('inside')
+      const last = document.getElementById('last')
+      const outside = document.getElementById('outside')
+
+      spyOn(SelectorEngine, 'focusableChildren').and.callFake(() => [first, inside, last])
+      spyOn(first, 'focus').and.callThrough()
+
+      const focusInListener = () => {
+        expect(first.focus).toHaveBeenCalled()
+        first.removeEventListener('focusin', focusInListener)
+        done()
+      }
+
+      first.addEventListener('focusin', focusInListener)
+
+      const keydown = createEvent('keydown')
+      keydown.key = 'Tab'
+
+      document.dispatchEvent(keydown)
+      outside.focus()
+    })
+
+    it('should wrap focus around backwards on shift-tab', done => {
+      fixtureEl.innerHTML = [
+        '<a href="#" id="outside">outside</a>',
+        '<div id="focustrap" tabindex="-1">',
+        '   <a href="#" id="first">first</a>',
+        '   <a href="#" id="inside">inside</a>',
+        '   <a href="#" id="last">last</a>',
+        '</div>'
+      ].join('')
+
+      const trapElement = fixtureEl.querySelector('div')
+      const focustrap = new FocusTrap({ trapElement })
+      focustrap.activate()
+
+      const first = document.getElementById('first')
+      const inside = document.getElementById('inside')
+      const last = document.getElementById('last')
+      const outside = document.getElementById('outside')
+
+      spyOn(SelectorEngine, 'focusableChildren').and.callFake(() => [first, inside, last])
+      spyOn(last, 'focus').and.callThrough()
+
+      const focusInListener = () => {
+        expect(last.focus).toHaveBeenCalled()
+        last.removeEventListener('focusin', focusInListener)
+        done()
+      }
+
+      last.addEventListener('focusin', focusInListener)
+
+      const keydown = createEvent('keydown')
+      keydown.key = 'Tab'
+      keydown.shiftKey = true
+
+      document.dispatchEvent(keydown)
+      outside.focus()
+    })
+
+    it('should force focus on itself if there is no focusable content', done => {
+      fixtureEl.innerHTML = [
+        '<a href="#" id="outside">outside</a>',
+        '<div id="focustrap" tabindex="-1"></div>'
+      ].join('')
+
+      const trapElement = fixtureEl.querySelector('div')
+      const focustrap = new FocusTrap({ trapElement })
+      focustrap.activate()
+
+      const focusInListener = () => {
+        expect(focustrap._config.trapElement.focus).toHaveBeenCalled()
+        document.removeEventListener('focusin', focusInListener)
+        done()
+      }
+
+      spyOn(focustrap._config.trapElement, 'focus')
+
+      document.addEventListener('focusin', focusInListener)
+
+      const focusInEvent = createEvent('focusin', { bubbles: true })
+      Object.defineProperty(focusInEvent, 'target', {
+        value: document.getElementById('outside')
+      })
+
+      document.dispatchEvent(focusInEvent)
+    })
+  })
+
+  describe('deactivate', () => {
+    it('should flag itself as no longer active', () => {
+      const focustrap = new FocusTrap({ trapElement: fixtureEl })
+      focustrap.activate()
+      expect(focustrap._isActive).toBe(true)
+
+      focustrap.deactivate()
+      expect(focustrap._isActive).toBe(false)
+    })
+
+    it('should remove all event listeners', () => {
+      const focustrap = new FocusTrap({ trapElement: fixtureEl })
+      focustrap.activate()
+
+      spyOn(EventHandler, 'off')
+      focustrap.deactivate()
+
+      expect(EventHandler.off).toHaveBeenCalled()
+    })
+
+    it('doesn\'t try removing event listeners unless it needs to (in case it hasn\'t been activated)', () => {
+      const focustrap = new FocusTrap({ trapElement: fixtureEl })
+
+      spyOn(EventHandler, 'off')
+      focustrap.deactivate()
+
+      expect(EventHandler.off).not.toHaveBeenCalled()
+    })
+  })
+})