Update for compatibility with v12 rooms

src/components/structures/MatrixChat.tsx

@@ -141,6 +141,7 @@ import { type OpenForwardDialogPayload } from "../../dispatcher/payloads/OpenFor
 import { ShareFormat, type SharePayload } from "../../dispatcher/payloads/SharePayload";
 import Markdown from "../../Markdown";
 import { sanitizeHtmlParams } from "../../Linkify";
+import { isOnlyAdmin } from "../../utils/membership";
 
 // legacy export
 export { default as Views } from "../../Views";
@@ -1255,29 +1256,22 @@ export default class MatrixChat extends React.PureComponent<IProps, IState> {
 
         const client = MatrixClientPeg.get();
         if (client && roomToLeave) {
-            const plEvent = roomToLeave.currentState.getStateEvents(EventType.RoomPowerLevels, "");
-            const plContent = plEvent ? plEvent.getContent() : {};
-            const userLevels = plContent.users || {};
-            const currentUserLevel = userLevels[client.getUserId()!];
-            const userLevelValues = Object.values(userLevels);
-            if (userLevelValues.every((x) => typeof x === "number")) {
+            // If the user is the only user with highest power level
+            if (isOnlyAdmin(roomToLeave)) {
+                const userLevelValues = roomToLeave.getJoinedMembers().map((m) => m.powerLevel);
+
                 const maxUserLevel = Math.max(...(userLevelValues as number[]));
-                // If the user is the only user with highest power level
-                if (
-                    maxUserLevel === currentUserLevel &&
-                    userLevelValues.lastIndexOf(maxUserLevel) == userLevelValues.indexOf(maxUserLevel)
-                ) {
-                    const warning =
-                        maxUserLevel >= 100
-                            ? _t("leave_room_dialog|room_leave_admin_warning")
-                            : _t("leave_room_dialog|room_leave_mod_warning");
-                    warnings.push(
-                        <strong className="warning" key="last_admin_warning">
-                            {" " /* Whitespace, otherwise the sentences get smashed together */}
-                            {warning}
-                        </strong>,
-                    );
-                }
+
+                const warning =
+                    maxUserLevel >= 100
+                        ? _t("leave_room_dialog|room_leave_admin_warning")
+                        : _t("leave_room_dialog|room_leave_mod_warning");
+                warnings.push(
+                    <strong className="warning" key="last_admin_warning">
+                        {" " /* Whitespace, otherwise the sentences get smashed together */}
+                        {warning}
+                    </strong>,
+                );
             }
         }
 

src/components/views/dialogs/LeaveSpaceDialog.tsx

@@ -15,23 +15,13 @@ import BaseDialog from "../dialogs/BaseDialog";
 import SpaceStore from "../../../stores/spaces/SpaceStore";
 import SpaceChildrenPicker from "../spaces/SpaceChildrenPicker";
 import { filterBoolean } from "../../../utils/arrays";
+import { isOnlyAdmin } from "../../../utils/membership";
 
 interface IProps {
     space: Room;
     onFinished(leave: boolean, rooms?: Room[]): void;
 }
 
-const isOnlyAdmin = (room: Room): boolean => {
-    const userId = room.client.getSafeUserId();
-    if (room.getMember(userId)?.powerLevelNorm !== 100) {
-        return false; // user is not an admin
-    }
-    return room.getJoinedMembers().every((member) => {
-        // return true if every other member has a lower power level (we are highest)
-        return member.userId === userId || member.powerLevelNorm < 100;
-    });
-};
-
 const LeaveSpaceDialog: React.FC<IProps> = ({ space, onFinished }) => {
     const spaceChildren = useMemo(() => {
         const roomSet = new Set(SpaceStore.instance.getSpaceFilteredRoomIds(space.roomId));

src/utils/membership.ts

@@ -131,3 +131,23 @@ export async function waitForMember(
         client.removeListener(RoomStateEvent.NewMember, handler);
     });
 }
+
+/**
+ * Check if the user is the only joined admin in the room
+ * This function will *not* cause lazy loading of room members, so if these should be included then
+ * the caller needs to make sure members have been loaded.
+ * @param room The room to check if the user is the only admin.
+ * @returns True if the user is the only user with the highest power level, false otherwise
+ */
+export function isOnlyAdmin(room: Room): boolean {
+    const currentUserLevel = room.getMember(room.client.getSafeUserId())?.powerLevel;
+
+    const userLevelValues = room.getJoinedMembers().map((m) => m.powerLevel);
+
+    const maxUserLevel = Math.max(...userLevelValues.filter((x) => typeof x === "number"));
+    // If the user is the only user with highest power level
+    return (
+        maxUserLevel === currentUserLevel &&
+        userLevelValues.lastIndexOf(maxUserLevel) == userLevelValues.indexOf(maxUserLevel)
+    );
+}

test/unit-tests/components/structures/MatrixChat-test.tsx

@@ -691,6 +691,8 @@ describe("<MatrixChat />", () => {
                     jest.spyOn(spaceRoom, "isSpaceRoom").mockReturnValue(true);
 
                     jest.spyOn(ReleaseAnnouncementStore.instance, "getReleaseAnnouncement").mockReturnValue(null);
+                    (room as any).client = mockClient;
+                    (spaceRoom as any).client = mockClient;
                 });
 
                 describe("forget_room", () => {
@@ -775,6 +777,22 @@ describe("<MatrixChat />", () => {
                                 ),
                             ).toBeInTheDocument();
                         });
+                        it("should warn when user is the last admin", async () => {
+                            jest.spyOn(room, "getJoinedMembers").mockReturnValue([
+                                { powerLevel: 100 } as unknown as MatrixJs.RoomMember,
+                                { powerLevel: 0 } as unknown as MatrixJs.RoomMember,
+                            ]);
+                            jest.spyOn(room, "getMember").mockReturnValue({
+                                powerLevel: 100,
+                            } as unknown as MatrixJs.RoomMember);
+                            dispatchAction();
+                            await screen.findByRole("dialog");
+                            expect(
+                                screen.getByText(
+                                    "You're the only administrator in this room. If you leave, nobody will be able to change room settings or take other important actions.",
+                                ),
+                            ).toBeInTheDocument();
+                        });
                         it("should do nothing on cancel", async () => {
                             dispatchAction();
                             const dialog = await screen.findByRole("dialog");

test/unit-tests/components/views/dialogs/LeaveSpaceDialog-test.tsx

@@ -0,0 +1,50 @@
+/*
+Copyright 2025 New Vector 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.
+*/
+
+import React from "react";
+import { render, screen } from "jest-matrix-react";
+import { MatrixEvent, type RoomMember } from "matrix-js-sdk/src/matrix";
+
+import LeaveSpaceDialog from "../../../../../src/components/views/dialogs/LeaveSpaceDialog";
+import { createTestClient, mkStubRoom } from "../../../../test-utils";
+
+describe("LeaveSpaceDialog", () => {
+    it("should warn about not being able to rejoin non-public space", () => {
+        const mockClient = createTestClient();
+        const mockSpace = mkStubRoom("myfakeroom", "myfakeroom", mockClient) as any;
+        jest.spyOn(mockSpace.currentState, "getStateEvents").mockReturnValue(
+            new MatrixEvent({
+                type: "m.room.join_rules",
+                content: {
+                    join_rule: "invite",
+                },
+            }),
+        );
+
+        render(<LeaveSpaceDialog space={mockSpace} onFinished={jest.fn()} />);
+
+        expect(screen.getByText(/You won't be able to rejoin unless you are re-invited/)).toBeInTheDocument();
+    });
+
+    it("should warn if user is the only admin", () => {
+        const mockClient = createTestClient();
+        const mockSpace = mkStubRoom("myfakeroom", "myfakeroom", mockClient) as any;
+        jest.spyOn(mockSpace, "getJoinedMembers").mockReturnValue([
+            { powerLevel: 100 } as unknown as RoomMember,
+            { powerLevel: 0 } as unknown as RoomMember,
+        ]);
+        jest.spyOn(mockSpace, "getMember").mockReturnValue({
+            powerLevel: 100,
+        } as unknown as RoomMember);
+
+        render(<LeaveSpaceDialog space={mockSpace} onFinished={jest.fn()} />);
+
+        expect(
+            screen.getByText(/You're the only admin of this space. Leaving it will mean no one has control over it./),
+        ).toBeInTheDocument();
+    });
+});