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

src/d2m/actions/add-reaction.js

@@ -25,7 +25,7 @@ async function addReaction(data) {
 	if (!parentID) return // Nothing can be done if the parent message was never bridged.
 	assert.equal(typeof parentID, "string")
 
-	const key = await emojiToKey.emojiToKey(data.emoji)
+	const key = await emojiToKey.emojiToKey(data.emoji, data.message_id)
 	const shortcode = key.startsWith("mxc://") ? `:${data.emoji.name}:` : undefined
 
 	const roomID = await createRoom.ensureRoom(data.channel_id)

src/d2m/actions/remove-reaction.js

@@ -43,7 +43,7 @@ async function removeSomeReactions(data) {
  * @param {Ty.Event.Outer<Ty.Event.M_Reaction>[]} reactions
  */
 async function removeReaction(data, reactions) {
-	const key = await emojiToKey.emojiToKey(data.emoji)
+	const key = await emojiToKey.emojiToKey(data.emoji, data.message_id)
 	return converter.removeReaction(data, reactions, key)
 }
 
@@ -52,7 +52,7 @@ async function removeReaction(data, reactions) {
  * @param {Ty.Event.Outer<Ty.Event.M_Reaction>[]} reactions
  */
 async function removeEmojiReaction(data, reactions) {
-	const key = await emojiToKey.emojiToKey(data.emoji)
+	const key = await emojiToKey.emojiToKey(data.emoji, data.message_id)
 	const discordPreferredEncoding = await emoji.encodeEmoji(key, undefined)
 	db.prepare("DELETE FROM reaction WHERE message_id = ? AND encoded_emoji = ?").run(data.message_id, discordPreferredEncoding)
 

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) {

src/db/migrations/0023-add-original-encoding-to-reaction.sql

@@ -0,0 +1,5 @@
+BEGIN TRANSACTION;
+
+ALTER TABLE reaction ADD COLUMN original_encoding TEXT;
+
+COMMIT;

src/db/orm-defs.d.ts

@@ -110,6 +110,7 @@ export type Models = {
 		hashed_event_id: number
 		message_id: string
 		encoded_emoji: string
+		original_encoding: string | null
 	}
 
 	auto_emoji: {

src/m2d/actions/add-reaction.js

@@ -38,7 +38,7 @@ async function addReaction(event) {
 		throw e
 	}
 
-	db.prepare("REPLACE INTO reaction (hashed_event_id, message_id, encoded_emoji) VALUES (?, ?, ?)").run(utils.getEventIDHash(event.event_id), messageID, discordPreferredEncoding)
+	db.prepare("REPLACE INTO reaction (hashed_event_id, message_id, encoded_emoji, original_encoding) VALUES (?, ?, ?, ?)").run(utils.getEventIDHash(event.event_id), messageID, discordPreferredEncoding, key)
 }
 
 module.exports.addReaction = addReaction