Support additional_creators in /upgraderoom (MSC4289) (#31934)

Signed-off-by: Andy Balaam <andy.balaam@matrix.org>

src/SlashCommands.tsx

@@ -61,6 +61,7 @@ import { CommandCategories } from "./slash-commands/interface";
 import { Command } from "./slash-commands/command";
 import { goto, join } from "./slash-commands/join";
 import { manuallyVerifyDevice } from "./components/views/dialogs/ManualDeviceKeyVerificationDialog";
+import { parseUpgradeRoomArgs } from "./slash-commands/upgraderoom/parseUpgradeRoomArgs";
 
 export { CommandCategories, Command };
 
@@ -146,11 +147,15 @@ export const Commands = [
     }),
     new Command({
         command: "upgraderoom",
-        args: "<new_version>",
+        args: "<new_version> [<additional-creator-user-id> ...]",
         description: _td("slash_command|upgraderoom"),
         isEnabled: (cli) => !isCurrentLocalRoom(cli),
         runFn: function (cli, roomId, threadId, args) {
-            if (args) {
+            if (!args) {
+                return reject(this.getUsage());
+            }
+            const parsedArgs = parseUpgradeRoomArgs(args);
+            if (parsedArgs) {
                 const room = cli.getRoom(roomId);
                 if (!room?.currentState.mayClientSendStateEvent("m.room.tombstone", cli)) {
                     return reject(new UserFriendlyError("slash_command|upgraderoom_permission_error"));
@@ -158,7 +163,7 @@ export const Commands = [
 
                 const { finished } = Modal.createDialog(
                     RoomUpgradeWarningDialog,
-                    { roomId: roomId, targetVersion: args },
+                    { roomId: roomId, targetVersion: parsedArgs.targetVersion },
                     /*className=*/ undefined,
                     /*isPriority=*/ false,
                     /*isStatic=*/ true,
@@ -167,7 +172,17 @@ export const Commands = [
                 return success(
                     finished.then(async ([resp]): Promise<void> => {
                         if (!resp?.continue) return;
-                        await upgradeRoom(room, args, resp.invite);
+                        await upgradeRoom(
+                            room,
+                            parsedArgs.targetVersion,
+                            resp.invite,
+                            true,
+                            true,
+                            false,
+                            undefined,
+                            false,
+                            parsedArgs.additionalCreators,
+                        );
                     }),
                 );
             }

src/slash-commands/upgraderoom/parseUpgradeRoomArgs.ts

@@ -0,0 +1,33 @@
+/*
+ * Copyright 2026 Element Creations Ltd.
+ *
+ * SPDX-License-Identifier: AGPL-3.0-only OR GPL-3.0-only OR LicenseRef-Element-Commercial
+ * Please see LICENSE files in the repository root for full details.
+ */
+
+export type UpgradeRoomParsedArgs = {
+    targetVersion: string;
+    additionalCreators?: string[];
+};
+
+/**
+ * Parse the supplied arguments for a room upgrade, or return null if the
+ * arguments are not valid. The arguments must be a room version followed by
+ * zero or more valid user IDs.
+ */
+export function parseUpgradeRoomArgs(args: string): UpgradeRoomParsedArgs | null {
+    const parts = args.split(/\s+/);
+    if (parts.length === 0 || parts[0] === "") {
+        return null;
+    } else {
+        const targetVersion = parts[0];
+        let additionalCreators: string[] | undefined;
+        for (let i = 1; i < parts.length; ++i) {
+            if (additionalCreators === undefined) {
+                additionalCreators = [];
+            }
+            additionalCreators.push(parts[i]);
+        }
+        return { targetVersion, additionalCreators };
+    }
+}

src/utils/RoomUpgrade.ts

@@ -53,6 +53,7 @@ export async function upgradeRoom(
     awaitRoom = false,
     progressCallback?: (progress: RoomUpgradeProgress) => void,
     inhibitInviteProgressDialog = false,
+    additionalCreators?: string[],
 ): Promise<string> {
     const cli = room.client;
     let spinnerModal: IHandle<any> | undefined;
@@ -91,7 +92,7 @@ export async function upgradeRoom(
 
     let newRoomId: string;
     try {
-        ({ replacement_room: newRoomId } = await cli.upgradeRoom(room.roomId, targetVersion));
+        ({ replacement_room: newRoomId } = await cli.upgradeRoom(room.roomId, targetVersion, additionalCreators));
     } catch (e) {
         if (!handleError) throw e;
         logger.error(e);