Fix error when transition classes contain new lines (#2871)

* fix DOMException when remove class with '\n' character in react 'transition' component

* Split classes on all whitespace

* Revert "fix DOMException when remove class with '\n' character in react 'transition' component"

This reverts commit 76e835441b9cb84a1d867e1a37496c55cae86179.

* fix typo

* Add test

* Fix CS

* Update changelog

---------

Co-authored-by: Jordan Pittman <jordan@cryptica.me>

packages/@headlessui-react/CHANGELOG.md

@@ -19,6 +19,7 @@ and this project adheres to [Semantic Versioning](https://semver.org/spec/v2.0.0
 - Fix infinite render-loop for `<Disclosure.Panel>` and `<Popover.Panel>` when `as={Fragment}` ([#2760](https://github.com/tailwindlabs/headlessui/pull/2760))
 - Fix VoiceOver bug for `Listbox` component in Chrome ([#2824](https://github.com/tailwindlabs/headlessui/pull/2824))
 - Fix outside click detection when component is mounted in the Shadow DOM ([#2866](https://github.com/tailwindlabs/headlessui/pull/2866))
+- Fix error when transition classes contain new lines ([#2871](https://github.com/tailwindlabs/headlessui/pull/2871))
 
 ### Added
 

packages/@headlessui-react/src/components/transitions/transition.test.tsx

@@ -1,6 +1,8 @@
 import { act as _act, fireEvent, render } from '@testing-library/react'
 import React, { Fragment, useEffect, useLayoutEffect, useRef, useState } from 'react'
+import { getByText } from '../../test-utils/accessibility-assertions'
 import { executeTimeline } from '../../test-utils/execute-timeline'
+import { click } from '../../test-utils/interactions'
 import { createSnapshot } from '../../test-utils/snapshot'
 import { suppressConsoleLogs } from '../../test-utils/suppress-console-logs'
 import { Transition } from './transition'
@@ -402,6 +404,57 @@ describe('Setup API', () => {
   })
 
   describe('transition classes', () => {
+    it('should support new lines in class lists', async () => {
+      function Example() {
+        let [show, setShow] = useState(true)
+
+        return (
+          <div>
+            <button onClick={() => setShow((v) => !v)}>toggle</button>
+
+            <Transition show={show} as="div" className={`foo1\nfoo2`} enter="enter" leave="leave">
+              Children
+            </Transition>
+          </div>
+        )
+      }
+
+      let { container } = await act(() => render(<Example />))
+
+      expect(container.firstChild).toMatchInlineSnapshot(`
+        <div>
+          <button>
+            toggle
+          </button>
+          <div
+            class="foo1
+        foo2"
+          >
+            Children
+          </div>
+        </div>
+      `)
+
+      await click(getByText('toggle'))
+
+      // TODO: This is not quite right
+      // The `foo1\nfoo2` should be gone
+      // I think this is a qurk of JSDOM
+      expect(container.firstChild).toMatchInlineSnapshot(`
+        <div>
+          <button>
+            toggle
+          </button>
+          <div
+            class="foo1
+        foo2 foo1 foo2 leave"
+          >
+            Children
+          </div>
+        </div>
+      `)
+    })
+
     it('should be possible to passthrough the transition classes', () => {
       let { container } = render(
         <Transition

packages/@headlessui-react/src/components/transitions/transition.tsx

@@ -37,8 +37,14 @@ type ContainerElement = MutableRefObject<HTMLElement | null>
 
 type TransitionDirection = 'enter' | 'leave' | 'idle'
 
+/**
+ * Split class lists by whitespace
+ *
+ * We can't check for just spaces as all whitespace characters are
+ * invalid in a class name, so we have to split on ANY whitespace.
+ */
 function splitClasses(classes: string = '') {
-  return classes.split(' ').filter((className) => className.trim().length > 1)
+  return classes.split(/\s+/).filter((className) => className.length > 1)
 }
 
 interface TransitionContextValues {

packages/@headlessui-vue/CHANGELOG.md

@@ -19,6 +19,7 @@ and this project adheres to [Semantic Versioning](https://semver.org/spec/v2.0.0
 - Fix missing `data-headlessui-state` attribute when `as="template"` ([#2787](https://github.com/tailwindlabs/headlessui/pull/2787))
 - Fix VoiceOver bug for `Listbox` component in Chrome ([#2824](https://github.com/tailwindlabs/headlessui/pull/2824))
 - Fix outside click detection when component is mounted in the Shadow DOM ([6846231](https://github.com/tailwindlabs/headlessui/commit/684623131b99d9e75dfc1c1f6d27244c334a95d9))
+- Fix error when transition classes contain new lines ([#2871](https://github.com/tailwindlabs/headlessui/pull/2871))
 
 ### Added
 

packages/@headlessui-vue/src/components/transitions/transition.ts

@@ -29,8 +29,14 @@ import { Reason, transition } from './utils/transition'
 
 type ID = ReturnType<typeof useId>
 
+/**
+ * Split class lists by whitespace
+ *
+ * We can't check for just spaces as all whitespace characters are
+ * invalid in a class name, so we have to split on ANY whitespace.
+ */
 function splitClasses(classes: string = '') {
-  return classes.split(' ').filter((className) => className.trim().length > 1)
+  return classes.split(/\s+/).filter((className) => className.length > 1)
 }
 
 interface TransitionContextValues {