From 6456a4f44ac6437fe6234c178a11b103671cf5f3 Mon Sep 17 00:00:00 2001
From: Rafael dos Santos Silva <xfalcox@gmail.com>
Date: Thu, 28 Nov 2024 14:25:15 -0300
Subject: [PATCH] FIX: Keep related topics data cached when a user scrolls up
 (#976)

See https://meta.discourse.org/t/related-topics-missing-after-rereading-a-topic-with-more-than-20-posts/306147/6
---
 assets/javascripts/initializers/related-topics.gjs | 8 +++++++-
 1 file changed, 7 insertions(+), 1 deletion(-)

diff --git a/assets/javascripts/initializers/related-topics.gjs b/assets/javascripts/initializers/related-topics.gjs
index d03bda4e..89d2e037 100644
--- a/assets/javascripts/initializers/related-topics.gjs
+++ b/assets/javascripts/initializers/related-topics.gjs
@@ -47,10 +47,16 @@ export default {
         (Superclass) =>
           class extends Superclass {
             @tracked related_topics;
+            relatedTopicsCache = [];
 
             @cached
             get relatedTopics() {
-              return this.related_topics?.map((topic) =>
+              // Used to keep related topics when a user scrolls up from the
+              // bottom of the topic and then scrolls back down
+              if (this.related_topics) {
+                this.relatedTopicsCache = this.related_topics;
+              }
+              return this.relatedTopicsCache?.map((topic) =>
                 this.store.createRecord("topic", topic)
               );
             }