fix(ext/websocket): Avoid write deadlock that requires read_frame to complete (#18705)

Fixes https://github.com/denoland/deno/issues/18700

Timeline of the events that lead to the bug.

1. WebSocket handshake complete
2. Server on `read_frame` holding an AsyncRefCell borrow of the
WebSocket stream.
3. Client sends a TXT frame after a some time
4. Server recieves the frame and goes back to `read_frame`.
5. After some time, Server starts a `write_frame` but `read_frame` is
still holding a borrow!
^--- Locked. read_frame needs to complete so we can resume the write.

This commit changes all writes to directly borrow the
`fastwebsocket::WebSocket` resource under the assumption that it won't
affect ongoing reads.

1 files changed, 46 insertions, 0 deletions

diff --git a/cli/tests/unit/websocket_test.ts b/cli/tests/unit/websocket_test.ts
index 6737edc11..948e2add2 100644
--- a/cli/tests/unit/websocket_test.ts
+++ b/cli/tests/unit/websocket_test.ts
@@ -36,3 +36,49 @@ Deno.test(async function websocketPingPong() {
   await promise;
   ws.close();
 });
+
+// https://github.com/denoland/deno/issues/18700
+Deno.test(
+  { sanitizeOps: false, sanitizeResources: false },
+  async function websocketWriteLock() {
+    const ac = new AbortController();
+    const listeningPromise = deferred();
+
+    const server = Deno.serve({
+      handler: (req) => {
+        const { socket, response } = Deno.upgradeWebSocket(req);
+        socket.onopen = function () {
+          setTimeout(() => socket.send("Hello"), 500);
+        };
+        socket.onmessage = function (e) {
+          assertEquals(e.data, "Hello");
+          ac.abort();
+        };
+        return response;
+      },
+      signal: ac.signal,
+      onListen: () => listeningPromise.resolve(),
+      hostname: "localhost",
+      port: 4246,
+    });
+
+    await listeningPromise;
+    const promise = deferred();
+    const ws = new WebSocket("ws://localhost:4246/");
+    assertEquals(ws.url, "ws://localhost:4246/");
+    ws.onerror = () => fail();
+    ws.onmessage = (e) => {
+      assertEquals(e.data, "Hello");
+      setTimeout(() => {
+        ws.send(e.data);
+      }, 1000);
+      promise.resolve();
+    };
+    ws.onclose = () => {
+      promise.resolve();
+    };
+
+    await Promise.all([promise, server]);
+    ws.close();
+  },
+);