ReadableStream.cancel never trigger

[unnoq]

ReadableStream.cancel should be triggered when the user cancels a response before it finishes.

Currently, only "aborted" is printted, while "cancelled" never prints when a response is canceled before completion.

"@hono/node-server": "^1.19.4",

import { serve } from "@hono/node-server";

serve({
    fetch: ({ signal }) => {
        signal?.addEventListener("abort", () => console.log("aborted"));

        return new Response(new ReadableStream({
            async pull(controller) {
                controller.enqueue(new TextEncoder().encode("Hello, World!"));
                await new Promise((resolve) => setTimeout(resolve, 1000));
            },
            async cancel() {
                console.log("cancelled");
            }
        }), {
            headers: {
                "content-type": "text/event-stream"
            }
        })
    },
    port: 3000,
});

[usualoma]

Hi @unnoq, thank you for your comment. We will look into it.

We may need to review the details of the following changes.
#258

[usualoma]

What kind of usage is ReadableStream intended for?

As shown in the example below, it is expected that when an instance of ReadableStream no longer needs to generate data, cancel() is called, and upon being called, it should stop generating data itself.

https://developer.mozilla.org/en-US/docs/Web/API/ReadableStream/ReadableStream#examples

Examples mentioned in #239

In the example mentioned below, an error occurs because the generation started within start() does not stop when cancel() is called.

#239

In response to this, #258 addressed the issue by preventing cancel() from being called. However, I believe the correct approach would have been to leave the code calling cancel() unchanged and instead modify the application side.

How does it behave in other runtimes?

I have prepared the repository.

https://github.com/usualoma/hono-stream-cancel

app.ts

This is the implementation using pull() shown in the example for this issue.

When executed as follows, only node-server does not output "cancel".

# Confirmation of bun's behavior
$ bun run --hot app.ts &
$ curl -N http://localhost:3000/

# Confirmation of deno's behavior
$ deno serve app.ts &
$ curl -N http://localhost:8000/

# Confirmation of node-server's behavior
$ npx tsx app-node.ts &
$ curl -N http://localhost:3000/

app2.ts

This is the implementation in #239 that uses only start() without pull().

An error occurs in bun or deno.

https://github.com/usualoma/hono-stream-cancel/blob/main/fix-app2.patch

[unnoq]

@usualoma Thanks for your response. I believe this is a critical issue that should be fixed as soon as possible.

For context: I'm the author of oRPC. We have a feature called Event Iterator, and we rely on .cancel to trigger cleanup of the event iterator by invoking its .return. You can see the implementation here: https://github.com/unnoq/orpc/blob/main/packages/standard-server-fetch/src/event-iterator.ts#L226