fix(YouTube): destroy player on unmount to fix memory leak in v2

src/players/YouTube.js

@@ -20,6 +20,21 @@ export default class YouTube extends Component {
     this.props.onMount && this.props.onMount(this)
   }
 
+  componentWillUnmount () {
+    // The YouTube iframe API keeps a reference to every player it creates, so
+    // removing the container from the DOM is not enough to release the iframe.
+    // Without destroy() the iframe stays detached but reachable from window.YT,
+    // leaking the player and everything its event handlers close over.
+    if (this.player && typeof this.player.destroy === 'function') {
+      try {
+        this.player.destroy()
+      } catch (error) {
+        // destroy() throws if the iframe has already been removed
+      }
+    }
+    this.player = null
+  }
+
   getID (url) {
     if (!url || url instanceof Array || MATCH_PLAYLIST.test(url)) {
       return null

test/players/YouTube.js

@@ -78,6 +78,32 @@ test('load() when ready', t => {
   getSDK.restore()
 })
 
+test('componentWillUnmount() destroys the player', t => {
+  const destroy = sinon.fake()
+  const renderer = create(<YouTube url={TEST_URL} config={TEST_CONFIG} />)
+  const instance = renderer.getInstance()
+  instance.player = { destroy }
+  renderer.unmount()
+  t.ok(destroy.calledOnce, 'destroy() is called on unmount')
+  t.ok(instance.player === null, 'the player reference is released')
+})
+
+test('componentWillUnmount() without a player', t => {
+  const renderer = create(<YouTube url={TEST_URL} config={TEST_CONFIG} />)
+  renderer.unmount()
+  t.ok(true, 'unmounting before the player is ready does not throw')
+})
+
+test('componentWillUnmount() when destroy() throws', t => {
+  const renderer = create(<YouTube url={TEST_URL} config={TEST_CONFIG} />)
+  const instance = renderer.getInstance()
+  instance.player = {
+    destroy: () => { throw new Error('The YouTube player is not attached to the DOM') }
+  }
+  renderer.unmount()
+  t.ok(instance.player === null, 'a throwing destroy() does not break unmounting')
+})
+
 test('onStateChange() - play', t => {
   const called = {}
   const onPlay = () => { called.onPlay = true }