[SDK] fix slots missing initial status value

sdk/src/RTCSlot.test.ts

@@ -0,0 +1,71 @@
+/*
+Copyright 2026 Element Creations Ltd.
+
+SPDX-License-Identifier: AGPL-3.0-only OR LicenseRef-Element-Commercial
+Please see LICENSE in the repository root for full details.
+*/
+
+import { describe, expect, it } from "vitest";
+import { type MatrixClient, type Room } from "matrix-js-sdk";
+import { EventType } from "matrix-js-sdk/lib/@types/event";
+import { type MatrixEvent } from "matrix-js-sdk/lib/models/event";
+import {
+  type RoomState,
+  RoomStateEvent,
+} from "matrix-js-sdk/lib/models/room-state";
+
+import { createRTCSlot } from "./RTCSlot";
+import { type RTCSlotOptions } from "./api";
+import { MatrixRTCMode } from "./config";
+import { E2eeType } from "./encryption";
+import { mockEmitter, MockRTCSession, testScope } from "./utils/test";
+
+const options: RTCSlotOptions = {
+  matrixRTCMode: MatrixRTCMode.Compatibility,
+  encryptionSystem: { kind: E2eeType.NONE },
+};
+
+function setup(): {
+  client: MatrixClient;
+  room: Room;
+  session: MockRTCSession;
+} {
+  const room = {
+    ...mockEmitter(),
+    roomId: "!room:example.org",
+    getMembersWithMembership: (): [] => [],
+  } as unknown as Room;
+  const session = new MockRTCSession(room);
+  const client = {
+    getUserId: (): string => "@alice:example.org",
+    getDeviceId: (): string => "AAAA",
+    matrixRTC: { getRoomSession: (): MockRTCSession => session },
+  } as unknown as MatrixClient;
+  return { client, room, session };
+}
+
+describe("createRTCSlot", () => {
+  describe("status$", () => {
+    it("is undefined while the room has no slot event", () => {
+      const { client, room } = setup();
+      const slot = createRTCSlot(testScope(), client, room, options);
+      expect(slot.status$.value).toBeUndefined();
+    });
+
+    it("follows the slot event", () => {
+      const { client, room, session } = setup();
+      session.rtcSlot = { status: "open" };
+      const slot = createRTCSlot(testScope(), client, room, options);
+      expect(slot.status$.value).toBe("open");
+
+      session.rtcSlot = { status: "closed" };
+      room.emit(
+        RoomStateEvent.Events,
+        { getType: (): string => EventType.RTCSlot } as MatrixEvent,
+        {} as RoomState,
+        null,
+      );
+      expect(slot.status$.value).toBe("closed");
+    });
+  });
+});

sdk/src/RTCSlot.ts

@@ -15,7 +15,15 @@ import {
 } from "matrix-js-sdk/lib/matrixrtc";
 import { type MatrixEvent } from "matrix-js-sdk/lib/models/event";
 import { RoomStateEvent } from "matrix-js-sdk/lib/models/room-state";
-import { BehaviorSubject, filter, fromEvent, map, of, switchMap } from "rxjs";
+import {
+  BehaviorSubject,
+  filter,
+  fromEvent,
+  map,
+  of,
+  startWith,
+  switchMap,
+} from "rxjs";
 
 import { ObservableScope } from "./reactive/ObservableScope";
 import { generateItems } from "./reactive/observable";
@@ -108,12 +116,14 @@ export function createRTCSlot(
     ),
   );
 
+  // The status is undefined while the room has no slot event, and an explicit
+  // undefined is not an initial value to `behavior`, so it goes in the stream
   const status$ = scope.behavior(
     fromEvent(room, RoomStateEvent.Events, (event: MatrixEvent) => event).pipe(
       filter((event) => event.getType() === EventType.RTCSlot),
       map(() => slotStatus(jsSdkSession)),
+      startWith(slotStatus(jsSdkSession)),
     ),
-    slotStatus(jsSdkSession),
   );
 
   const slot: RTCSlot = {

sdk/src/utils/test.ts

@@ -273,6 +273,12 @@ export class MockRTCSession extends TypedEventEmitter<
     return this.joined;
   }
 
+  /** The slot event's content; undefined while the room has none. */
+  public rtcSlot: ReturnType<MatrixRTCSession["getRtcSlot"]> = undefined;
+  public getRtcSlot(): ReturnType<MatrixRTCSession["getRtcSlot"]> {
+    return this.rtcSlot;
+  }
+
   public isKeyRotationSuppressed = false;
 
   public withMemberships(