fix: handle abort requests

Author: darrachequesne

lib/transports/polling.ts

@@ -38,7 +38,7 @@ export class Polling extends Transport {
    * @private
    */
   private onPollRequest(
-    _req: Request,
+    req: Request,
     responseHeaders: Headers,
   ): Promise<Response> {
     if (this.pollingPromise) {
@@ -51,6 +51,10 @@ export class Polling extends Transport {
 
     debug("new polling request");
 
+    req.signal.addEventListener("abort", () => {
+      this.onError("polling request aborted");
+    });
+
     return new Promise<Response>((resolve, reject) => {
       this.pollingPromise = { resolve, reject, responseHeaders };
 
@@ -72,6 +76,10 @@ export class Polling extends Transport {
   ): Promise<Response> {
     debug("new data request");
 
+    req.signal.addEventListener("abort", () => {
+      this.onError("data request aborted");
+    });
+
     const data = await req.text();
 
     if (data.length > this.opts.maxHttpBufferSize) {

test/engine.test.ts

@@ -14,6 +14,7 @@ async function initLongPollingSession() {
   return JSON.parse(content.substring(1)).sid;
 }
 
+// imported from https://github.com/socketio/socket.io/blob/main/docs/engine.io-protocol/v4-test-suite
 describe("Engine.IO protocol", () => {
   beforeAll(() => {
     const engine = new Server({
@@ -313,6 +314,25 @@ describe("Engine.IO protocol", () => {
 
         expect(pollResponse.status).toEqual(400);
       });
+
+      it("closes the session upon cancelled polling request", async () => {
+        const sid = await initLongPollingSession();
+        const controller = new AbortController();
+
+        fetch(`${URL}/engine.io/?EIO=4&transport=polling&sid=${sid}`, {
+          signal: controller.signal,
+        }).catch(() => {});
+
+        await sleep(5);
+
+        controller.abort();
+
+        const pollResponse = await fetch(
+          `${URL}/engine.io/?EIO=4&transport=polling&sid=${sid}`,
+        );
+
+        expect(pollResponse.status).toEqual(400);
+      });
     });
 
     describe("WebSocket", () => {

test/socket.test.ts

@@ -25,6 +25,7 @@ async function initSocketIOConnection() {
   return socket;
 }
 
+// imported from https://github.com/socketio/socket.io/tree/main/docs/socket.io-protocol/v5-test-suite
 describe("Socket.IO protocol", () => {
   beforeAll(() => {
     const io = new Server();