refactor: do not persist session if connection state recovery if disabled

This is a follow-up commit of [1]. Without it, adapter.persistSession()
would be called even if the connection state recovery feature was
disabled.

[1]: 54d5ee0

Author: darrachequesne

Diff for: lib/socket.ts

@@ -742,7 +742,10 @@ export class Socket<
     debug("closing socket - reason %s", reason);
     this.emitReserved("disconnecting", reason, description);
 
-    if (RECOVERABLE_DISCONNECT_REASONS.has(reason)) {
+    if (
+      this.server._opts.connectionStateRecovery &&
+      RECOVERABLE_DISCONNECT_REASONS.has(reason)
+    ) {
       debug("connection state recovery is enabled for sid %s", this.id);
       this.adapter.persistSession({
         sid: this.id,

Diff for: test/connection-state-recovery.ts

@@ -2,6 +2,7 @@ import { Server, Socket } from "..";
 import expect from "expect.js";
 import { waitFor, eioHandshake, eioPush, eioPoll } from "./support/util";
 import { createServer, Server as HttpServer } from "http";
+import { Adapter } from "socket.io-adapter";
 
 async function init(httpServer: HttpServer, io: Server) {
   // Engine.IO handshake
@@ -215,4 +216,32 @@ describe("connection state recovery", () => {
 
     io.close();
   });
+
+  it("should not call adapter#persistSession or adapter#restoreSession if disabled", async () => {
+    const httpServer = createServer().listen(0);
+
+    class DummyAdapter extends Adapter {
+      override persistSession(session) {
+        expect.fail();
+      }
+
+      override restoreSession(pid, offset) {
+        expect.fail();
+        return Promise.reject("should not happen");
+      }
+    }
+
+    const io = new Server(httpServer, {
+      adapter: DummyAdapter,
+    });
+
+    // Engine.IO handshake
+    const sid = await eioHandshake(httpServer);
+
+    await eioPush(httpServer, sid, '40{"pid":"foo","offset":"bar"}');
+    await eioPoll(httpServer, sid);
+    await eioPush(httpServer, sid, "1");
+
+    io.close();
+  });
 });