d->m: Fix reply to user join message

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

@@ -669,7 +669,7 @@ async function messageToEvent(message, guild, options = {}, di) {
 					const match = repliedToEventSenderMxid.match(/^@([^:]*)/)
 					assert(match)
 					repliedToDisplayName = referenced.author.username || match[1] || "a Matrix user" // grab the localpart as the display name, whatever
-					repliedToUserHtml = `<a href="https://matrix.to/#/${repliedToEventSenderMxid}">${repliedToDisplayName}</a>`
+					repliedToUserHtml = tag`<a href="https://matrix.to/#/${repliedToEventSenderMxid}">${repliedToDisplayName}</a>`
 				} else {
 					repliedToDisplayName = referenced.author.global_name || referenced.author.username || "a Discord user"
 					repliedToUserHtml = repliedToDisplayName
@@ -694,6 +694,12 @@ async function messageToEvent(message, guild, options = {}, di) {
 						+ html
 					body = `${repliedToDisplayName}: ${repliedToBody}`.split("\n").map(line => "> " + line).join("\n") // scenario 1 part B for mentions
 						+ "\n\n" + body
+				} else if (referenced.type === DiscordTypes.MessageType.UserJoin) {
+					// Discord user join messages are bridged as joins, not text events. Generate substitute text for reply.
+					const joinerMxid = select("sim", "mxid", {user_id: referenced.author.id}).pluck().get()
+					const joinerHtml = joinerMxid ? tag`<a href="https://matrix.to/#/${joinerMxid}">${repliedToDisplayName}</a>` : tag`<strong>${repliedToDisplayName}</strong>`
+					html = `<blockquote>${joinerHtml} joined the room</blockquote>` + html
+					body = `> ${repliedToDisplayName} joined the room\n\n` + body
 				} else { // repliedToUnknownEvent
 					const dateDisplay = dUtils.howOldUnbridgedMessage(referenced.timestamp, message.timestamp)
 					html = `<blockquote>In reply to ${dateDisplay} from ${repliedToDisplayName}:`

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

@@ -4,6 +4,7 @@ const {MatrixServerError} = require("../../matrix/mreq")
 const data = require("../../../test/data")
 const {mockGetEffectivePower} = require("../../matrix/utils.test")
 const Ty = require("../../types")
+const {db} = require("../../passthrough")
 
 /**
  * @param {string} roomID
@@ -733,6 +734,31 @@ test("message2event: reply to a Discord message that wasn't bridged", async t =>
 	}])
 })
 
+test("message2event: reply to a Discord member join (who didn't join on Matrix)", async t => {
+	const events = await messageToEvent(data.message.reply_to_member_join, data.guild.general)
+	t.deepEqual(events, [{
+		$type: "m.room.message",
+		msgtype: "m.text",
+		body: "> PEASANT!! joined the room\n\nwhen the broke friend who we pay to bring food shows up at the medieval lord party",
+		format: "org.matrix.custom.html",
+		formatted_body: "<blockquote><strong>PEASANT!!</strong> joined the room</blockquote>when the broke friend who we pay to bring food shows up at the medieval lord party",
+		"m.mentions": {}
+	}])
+})
+
+test("message2event: reply to a Discord member join (who did join on Matrix)", async t => {
+	db.prepare("INSERT INTO sim (user_id, username, sim_name, mxid) VALUES ('1461677775554478161', 'peasant321_76775', 'peasant321_76775', '@_ooye_peasant321_76775:cadence.moe')").run()
+	const events = await messageToEvent(data.message.reply_to_member_join, data.guild.general)
+	t.deepEqual(events, [{
+		$type: "m.room.message",
+		msgtype: "m.text",
+		body: "> PEASANT!! joined the room\n\nwhen the broke friend who we pay to bring food shows up at the medieval lord party",
+		format: "org.matrix.custom.html",
+		formatted_body: `<blockquote><a href="https://matrix.to/#/@_ooye_peasant321_76775:cadence.moe">PEASANT!!</a> joined the room</blockquote>when the broke friend who we pay to bring food shows up at the medieval lord party`,
+		"m.mentions": {}
+	}])
+})
+
 test("message2event: simple written @mention for matrix user", async t => {
 	const events = await messageToEvent(data.message.simple_written_at_mention_for_matrix, data.guild.general, {}, {
 		api: {