From 2696f02ce1b08f4db1a54c2f98f52a36546dd8a8 Mon Sep 17 00:00:00 2001
From: Alexander Skvortsov <38059171+askvortsov1@users.noreply.github.com>
Date: Thu, 1 Oct 2020 14:50:54 -0400
Subject: [PATCH] Fix multiple scrolls to same post in PostStream (#2264)

While more pleasant from an FSM standpoint, comparing the current targetPost to the previous one does not work if goToNumber is called twice in a row for the same post. For instance, if a user clicks the mentions link to a post twice, the post stream breaks.
---
 framework/core/js/src/forum/components/PostStream.js  | 11 ++---------
 framework/core/js/src/forum/states/PostStreamState.js |  2 ++
 2 files changed, 4 insertions(+), 9 deletions(-)

diff --git a/framework/core/js/src/forum/components/PostStream.js b/framework/core/js/src/forum/components/PostStream.js
index 37ee017ae..a80f75bec 100644
--- a/framework/core/js/src/forum/components/PostStream.js
+++ b/framework/core/js/src/forum/components/PostStream.js
@@ -121,15 +121,10 @@ export default class PostStream extends Component {
    * Start scrolling, if appropriate, to a newly-targeted post.
    */
   triggerScroll() {
-    if (!this.attrs.targetPost) return;
+    if (!this.attrs.targetPost || !this.stream.needsScroll) return;
 
-    const oldTarget = this.prevTarget;
     const newTarget = this.attrs.targetPost;
-
-    if (oldTarget) {
-      if ('number' in oldTarget && oldTarget.number === newTarget.number) return;
-      if ('index' in oldTarget && oldTarget.index === newTarget.index) return;
-    }
+    this.stream.needsScroll = false;
 
     if ('number' in newTarget) {
       this.scrollToNumber(newTarget.number, this.stream.animateScroll);
@@ -137,8 +132,6 @@ export default class PostStream extends Component {
       const backwards = newTarget.index === this.stream.count() - 1;
       this.scrollToIndex(newTarget.index, this.stream.animateScroll, backwards);
     }
-
-    this.prevTarget = newTarget;
   }
 
   /**
diff --git a/framework/core/js/src/forum/states/PostStreamState.js b/framework/core/js/src/forum/states/PostStreamState.js
index 2c827bff3..8f93e8f1f 100644
--- a/framework/core/js/src/forum/states/PostStreamState.js
+++ b/framework/core/js/src/forum/states/PostStreamState.js
@@ -103,6 +103,7 @@ class PostStreamState {
 
     this.loadPromise = this.loadNearNumber(number);
 
+    this.needsScroll = true;
     this.targetPost = { number };
     this.animateScroll = !noAnimation;
     this.number = number;
@@ -127,6 +128,7 @@ class PostStreamState {
 
     this.loadPromise = this.loadNearIndex(index);
 
+    this.needsScroll = true;
     this.targetPost = { index };
     this.animateScroll = !noAnimation;
     this.index = index;