Fix clicking on already-opened thread post scrolling to the top of the thread (#27331)

app/javascript/mastodon/features/status/index.jsx

@@ -607,6 +607,22 @@ class Status extends ImmutablePureComponent {
     this.setState({ fullscreen: isFullscreen() });
   };
 
+  shouldUpdateScroll = (prevRouterProps, { location }) => {
+    // Do not change scroll when opening a modal
+    if (location.state?.mastodonModalKey && location.state?.mastodonModalKey !== prevRouterProps?.location?.state?.mastodonModalKey) {
+      return false;
+    }
+
+    // Scroll to focused post if it is loaded
+    const child = this.node?.querySelector('.detailed-status__wrapper');
+    if (child) {
+      return [0, child.offsetTop];
+    }
+
+    // Do not scroll otherwise, `componentDidUpdate` will take care of that
+    return false;
+  };
+
   render () {
     let ancestors, descendants;
     const { isLoading, status, ancestorsIds, descendantsIds, intl, domain, multiColumn, pictureInPicture } = this.props;
@@ -660,7 +676,7 @@ class Status extends ImmutablePureComponent {
           )}
         />
 
-        <ScrollContainer scrollKey='thread'>
+        <ScrollContainer scrollKey='thread' shouldUpdateScroll={this.shouldUpdateScroll}>
           <div className={classNames('scrollable', { fullscreen })} ref={this.setRef}>
             {ancestors}