Fix m->d then d->m reactions not merging

src/d2m/converters/emoji-to-key.js

@@ -8,9 +8,10 @@ const file = sync.require("../../matrix/file")
 
 /**
  * @param {import("discord-api-types/v10").APIEmoji} emoji
+ * @param {string} message_id
  * @returns {Promise<string>}
  */
-async function emojiToKey(emoji) {
+async function emojiToKey(emoji, message_id) {
 	let key
 	if (emoji.id) {
 		// Custom emoji
@@ -30,7 +31,10 @@ async function emojiToKey(emoji) {
 		// Default emoji
 		const name = emoji.name
 		assert(name)
-		key = name
+		// If the reaction was used on Matrix already, it might be using a different arrangement of Variation Selector 16 characters.
+		// We'll use the same arrangement that was originally used, otherwise a duplicate of the emoji will appear as a separate reaction.
+		const originalEncoding = select("reaction", "original_encoding", {message_id, encoded_emoji: encodeURIComponent(name)}).pluck().get()
+		key = originalEncoding || name
 	}
 	return key
 }

src/d2m/converters/message-to-event.js

@@ -401,7 +401,7 @@ async function messageToEvent(message, guild, options = {}, di) {
 			const id = match[3]
 			const name = match[2]
 			const animated = !!match[1]
-			return emojiToKey.emojiToKey({id, name, animated}) // Register the custom emoji if needed
+			return emojiToKey.emojiToKey({id, name, animated}, message.id) // Register the custom emoji if needed
 		}))
 
 		async function transformParsedVia(parsed) {