fix(MessageReaction): fetching a removed partial custom emoji (#3955)

* fix: handling GuildEmoji within fetch()

* refactor: remove unused "private" methods

* refactor: make use of Message#fetch() to patch

src/managers/ReactionManager.js

@@ -64,32 +64,6 @@ class ReactionManager extends BaseManager {
       .reactions.delete()
       .then(() => this.message);
   }
-
-  _partial(emoji) {
-    const id = emoji.id || emoji.name;
-    const existing = this.cache.get(id);
-    return !existing || existing.partial;
-  }
-
-  async _fetchReaction(reactionEmoji, cache) {
-    const id = reactionEmoji.id || reactionEmoji.name;
-    const existing = this.cache.get(id);
-    if (!this._partial(reactionEmoji)) return existing;
-    const data = await this.client.api
-      .channels(this.message.channel.id)
-      .messages(this.message.id)
-      .get();
-    if (this.message.partial) this.message._patch(data);
-    if (!data.reactions || !data.reactions.some(r => (r.emoji.id || r.emoji.name) === id)) {
-      reactionEmoji.reaction._patch({ count: 0 });
-      this.message.reactions.cache.delete(id);
-      return existing;
-    }
-    for (const reaction of data.reactions) {
-      if (this._partial(reaction.emoji)) this.add(reaction, cache);
-    }
-    return existing;
-  }
 }
 
 module.exports = ReactionManager;

src/structures/MessageReaction.js

@@ -101,8 +101,12 @@ class MessageReaction {
    * Fetch this reaction.
    * @returns {Promise<MessageReaction>}
    */
-  fetch() {
+  async fetch() {
-    return this.message.reactions._fetchReaction(this.emoji, true);
+    const message = await this.message.fetch();
+    const existing = message.reactions.cache.get(this.emoji.id || this.emoji.name);
+    // The reaction won't get set when it has been completely removed
+    this._patch(existing || { count: 0 });
+    return this;
   }
 
   toJSON() {