Fix dropdown keys to open menu (#32750)

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

js/src/dropdown.js

@@ -468,6 +468,12 @@ class Dropdown extends BaseComponent {
       return
     }
 
+    if (!isActive && (event.key === ARROW_UP_KEY || event.key === ARROW_DOWN_KEY)) {
+      const button = this.matches(SELECTOR_DATA_TOGGLE) ? this : SelectorEngine.prev(this, SELECTOR_DATA_TOGGLE)[0]
+      button.click()
+      return
+    }
+
     if (!isActive || event.key === SPACE_KEY) {
       Dropdown.clearMenus()
       return

js/tests/unit/dropdown.spec.js

@@ -1626,4 +1626,52 @@ describe('Dropdown', () => {
       expect(Dropdown.getInstance(div)).toEqual(null)
     })
   })
+
+  it('should open dropdown when pressing keydown or keyup', done => {
+    fixtureEl.innerHTML = [
+      '<div class="dropdown">',
+      '  <button class="btn dropdown-toggle" data-bs-toggle="dropdown">Dropdown</button>',
+      '  <div class="dropdown-menu">',
+      '    <a class="dropdown-item disabled" href="#sub1">Submenu 1</a>',
+      '    <button class="dropdown-item" type="button" disabled>Disabled button</button>',
+      '    <a id="item1" class="dropdown-item" href="#">Another link</a>',
+      '  </div>',
+      '</div>'
+    ].join('')
+
+    const triggerDropdown = fixtureEl.querySelector('[data-bs-toggle="dropdown"]')
+    const dropdown = fixtureEl.querySelector('.dropdown')
+
+    const keydown = createEvent('keydown')
+    keydown.key = 'ArrowDown'
+
+    const keyup = createEvent('keyup')
+    keyup.key = 'ArrowUp'
+
+    const handleArrowDown = () => {
+      expect(triggerDropdown.classList.contains('show')).toEqual(true)
+      expect(triggerDropdown.getAttribute('aria-expanded')).toEqual('true')
+      setTimeout(() => {
+        dropdown.hide()
+        keydown.key = 'ArrowUp'
+        triggerDropdown.dispatchEvent(keyup)
+      }, 20)
+    }
+
+    const handleArrowUp = () => {
+      expect(triggerDropdown.classList.contains('show')).toEqual(true)
+      expect(triggerDropdown.getAttribute('aria-expanded')).toEqual('true')
+      done()
+    }
+
+    dropdown.addEventListener('shown.bs.dropdown', event => {
+      if (event.target.key === 'ArrowDown') {
+        handleArrowDown()
+      } else {
+        handleArrowUp()
+      }
+    })
+
+    triggerDropdown.dispatchEvent(keydown)
+  })
 })