fix: dedupe concurrent joins before auth resolution

Author: zxch3n

packages/loro-websocket/src/client/index.ts

@@ -1029,21 +1029,22 @@ export class LoroWebsocketClient {
       return room;
     });
 
+    // Register pending room immediately so concurrent join calls dedupe
+    this.pendingRooms.set(id, {
+      room,
+      resolve: resolve!,
+      reject: reject!,
+      adaptor: crdtAdaptor,
+      roomId,
+      auth: undefined,
+    });
     this.roomAuth.set(id, auth);
 
-    // Resolve auth before registering pending room to avoid race condition
-    // where JoinError retry might use undefined auth
     void this.resolveAuth(auth)
       .then(authValue => {
-        // Register pending room only after auth is resolved
-        this.pendingRooms.set(id, {
-          room,
-          resolve: resolve!,
-          reject: reject!,
-          adaptor: crdtAdaptor,
-          roomId,
-          auth: authValue,
-        });
+        const currentPending = this.pendingRooms.get(id);
+        if (!currentPending) return;
+        currentPending.auth = authValue;
 
         const joinPayload = encode({
           type: MessageType.JoinRequest,

packages/loro-websocket/tests/e2e.test.ts

@@ -618,6 +618,41 @@ describe("E2E: Client-Server Sync", () => {
     }
   }, 15000);
 
+  it("dedupes concurrent join calls even before auth resolves", async () => {
+    const port = await getPort();
+    const tokens: string[] = [];
+
+    const server = new SimpleServer({
+      port,
+      authenticate: async (_roomId, _crdt, auth) => {
+        tokens.push(new TextDecoder().decode(auth));
+        return "write";
+      },
+    });
+    await server.start();
+
+    const client = new LoroWebsocketClient({ url: `ws://localhost:${port}` });
+    await client.waitConnected();
+
+    const adaptor = new LoroAdaptor();
+    const auth = () => new TextEncoder().encode("token-once");
+
+    const joinPromise1 = client.join({ roomId: "dedupe", crdtAdaptor: adaptor, auth });
+    const joinPromise2 = client.join({ roomId: "dedupe", crdtAdaptor: adaptor, auth });
+
+    expect(joinPromise1).toBe(joinPromise2);
+
+    const [room1, room2] = await Promise.all([joinPromise1, joinPromise2]);
+    expect(room1).toBe(room2);
+
+    await waitUntil(() => tokens.length >= 1, 5000, 25);
+    expect(tokens).toHaveLength(1);
+
+    await room1.destroy();
+    client.destroy();
+    await server.stop();
+  }, 15000);
+
   it("destroy rejects pending ping waiters", async () => {
     const client = new LoroWebsocketClient({ url: `ws://localhost:${port}` });
     await client.waitConnected();