Fix expiring polls not being displayed as such in the WebUI (#11835)

* Fix expiring polls not being displayed as such in the WebUI

* Reset expiration state and timer when a poll changes

* Refactor timer logic in `_setupTimer`, only set expiration if props have changed

* Refactor and do not use deprecated React lifecycles

app/javascript/mastodon/components/poll.js

@@ -32,8 +32,38 @@ class Poll extends ImmutablePureComponent {
 
   state = {
     selected: {},
+    expired: null,
   };
 
+  static getDerivedStateFromProps (props, state) {
+    const { poll, intl } = props;
+    const expired = poll.get('expired') || (new Date(poll.get('expires_at'))).getTime() < intl.now();
+    return (expired === state.expired) ? null : { expired };
+  }
+
+  componentDidMount () {
+    this._setupTimer();
+  }
+
+  componentDidUpdate () {
+    this._setupTimer();
+  }
+
+  componentWillUnmount () {
+    clearTimeout(this._timer);
+  }
+
+  _setupTimer () {
+    const { poll, intl } = this.props;
+    clearTimeout(this._timer);
+    if (!this.state.expired) {
+      const delay = (new Date(poll.get('expires_at'))).getTime() - intl.now();
+      this._timer = setTimeout(() => {
+        this.setState({ expired: true });
+      }, delay);
+    }
+  }
+
   handleOptionChange = e => {
     const { target: { value } } = e;
 
@@ -68,12 +98,11 @@ class Poll extends ImmutablePureComponent {
     this.props.dispatch(fetchPoll(this.props.poll.get('id')));
   };
 
-  renderOption (option, optionIndex) {
+  renderOption (option, optionIndex, showResults) {
     const { poll, disabled } = this.props;
     const percent            = poll.get('votes_count') === 0 ? 0 : (option.get('votes_count') / poll.get('votes_count')) * 100;
     const leading            = poll.get('options').filterNot(other => other.get('title') === option.get('title')).every(other => option.get('votes_count') > other.get('votes_count'));
     const active             = !!this.state.selected[`${optionIndex}`];
-    const showResults        = poll.get('voted') || poll.get('expired');
 
     let titleEmojified = option.get('title_emojified');
     if (!titleEmojified) {
@@ -112,19 +141,20 @@ class Poll extends ImmutablePureComponent {
 
   render () {
     const { poll, intl } = this.props;
+    const { expired } = this.state;
 
     if (!poll) {
       return null;
     }
 
-    const timeRemaining = poll.get('expired') ? intl.formatMessage(messages.closed) : <RelativeTimestamp timestamp={poll.get('expires_at')} futureDate />;
-    const showResults   = poll.get('voted') || poll.get('expired');
+    const timeRemaining = expired ? intl.formatMessage(messages.closed) : <RelativeTimestamp timestamp={poll.get('expires_at')} futureDate />;
+    const showResults   = poll.get('voted') || expired;
     const disabled      = this.props.disabled || Object.entries(this.state.selected).every(item => !item);
 
     return (
       <div className='poll'>
         <ul>
-          {poll.get('options').map((option, i) => this.renderOption(option, i))}
+          {poll.get('options').map((option, i) => this.renderOption(option, i, showResults))}
         </ul>
 
         <div className='poll__footer'>