Fix and test broken room bridge check

A `m.room.member` handler check intended to determine whether a room was
bridged or not ended up checking the truthiness of the db query itself,
resulting in a tautology.

This commit fixes the check and moves it over to matrix/utils so it may
be reused and tested in isolation.

src/m2d/event-dispatcher.js

@@ -422,8 +422,7 @@ async event => {
 
 	if (utils.eventSenderIsFromDiscord(event.state_key)) return
 
-	const exists = select("channel_room", "room_id", {room_id: event.room_id}) ?? select("guild_space", "space_id", {space_id: event.room_id})
+	if (!utils.isBridgedRoom(event.room_id)) return // don't cache members in unbridged rooms
-	if (!exists) return // don't cache members in unbridged rooms
 
 	// Member is here
 	let {powers: {[event.state_key]: memberPower}, tombstone} = await utils.getEffectivePower(event.room_id, [event.state_key], api)

src/matrix/utils.js

@@ -4,7 +4,7 @@ const assert = require("assert").strict
 const Ty = require("../types")
 const {tag} = require("@cloudrac3r/html-template-tag")
 const passthrough = require("../passthrough")
-const {db} = passthrough
+const {db, select} = passthrough
 
 const {reg} = require("./read-registration")
 const userRegex = reg.namespaces.users.map(u => new RegExp(u.regex))
@@ -41,6 +41,16 @@ function eventSenderIsFromDiscord(sender) {
 	return false
 }
 
+/**
+ * @param {string} roomID
+ * @returns {boolean} whether the room is a bridged channel or space
+ */
+function isBridgedRoom(roomID) {
+	if (select("channel_room", "room_id", {room_id: roomID}).get()) return true
+	if (select("guild_space", "space_id", {space_id: roomID}).get()) return true
+	return false
+}
+
 /**
  * Event IDs are really big and have more entropy than we need.
  * If we want to store the event ID in the database, we can store a more compact version by hashing it with this.
@@ -388,6 +398,7 @@ async function setUserPowerCascade(spaceID, mxid, power, api) {
 module.exports.bot = bot
 module.exports.BLOCK_ELEMENTS = BLOCK_ELEMENTS
 module.exports.eventSenderIsFromDiscord = eventSenderIsFromDiscord
+module.exports.isBridgedRoom = isBridgedRoom
 module.exports.makeMxcPublic = makeMxcPublic
 module.exports.getPublicUrlForMxc = getPublicUrlForMxc
 module.exports.getEventIDHash = getEventIDHash

src/matrix/utils.test.js

@@ -2,7 +2,7 @@
 
 const {select} = require("../passthrough")
 const {test} = require("supertape")
-const {eventSenderIsFromDiscord, getEventIDHash, MatrixStringBuilder, getViaServers, roomHasAtLeastVersion, removeCreatorsFromPowerLevels, setUserPower} = require("./utils")
+const {eventSenderIsFromDiscord, isBridgedRoom, getEventIDHash, MatrixStringBuilder, getViaServers, roomHasAtLeastVersion, removeCreatorsFromPowerLevels, setUserPower} = require("./utils")
 const util = require("util")
 
 /** @param {string[]} mxids */
@@ -30,6 +30,18 @@ test("sender type: ooye puppet", t => {
 	t.ok(eventSenderIsFromDiscord("@_ooye_sheep:cadence.moe"))
 })
 
+test("is bridged room: channel room", t => {
+	t.equal(isBridgedRoom("!kLRqKKUQXcibIMtOpl:cadence.moe"), true)
+})
+
+test("is bridged room: space", t => {
+	t.equal(isBridgedRoom("!jjmvBegULiLucuWEHU:cadence.moe"), true)
+})
+
+test("is bridged room: unbridged room", t => {
+	t.equal(isBridgedRoom("!unbridged:cadence.moe"), false)
+})
+
 test("event hash: hash is the same each time", t => {
 	const eventID = "$example"
 	t.equal(getEventIDHash(eventID), getEventIDHash(eventID))