feat: add signal property to request in vite, node environments

.changeset/twelve-jokes-prove.md

@@ -0,0 +1,6 @@
+---
+'@sveltejs/adapter-node': minor
+'@sveltejs/kit': minor
+---
+
+feat: add signal property to request in vite, node environments

documentation/docs/25-build-and-deploy/40-adapter-node.md

@@ -263,3 +263,49 @@ app.listen(3000, () => {
 	console.log('listening on port 3000');
 });
 ```
+
+## Aborted requests
+
+> [!NOTE] This feature is available in `vite dev` and `vite preview` servers.
+
+The adapter will fire an `abort` event when the incoming request is cancelled before completion. You can access the [AbortSignal](https://developer.mozilla.org/en-US/docs/Web/API/AbortSignal) via `event.request.signal`.  
+
+A pretty typical example of using the `signal` property:
+
+```js
+/// file: src/routes/api/object/[slug]/+server.js
+/** @type {import('./$types').RequestHandler} */
+export async function GET({ request, params }) {
+    const stream = await s3.getObject("bucket", params.slug, {
+        signal: request.signal
+    }) 
+
+    return new Response(stream)
+}
+```
+
+Another example, this time using [Server-Sent Events](https://developer.mozilla.org/en-US/docs/Web/API/Server-sent_events):
+
+```js
+/// file: src/routes/api/sse/+server.js
+/** @type {import('./$types').RequestHandler} */
+export function GET({ request }) {
+    const stream = new ReadableStream({
+        start(controller) {
+            const interval = setInterval(() => {
+                controller.enqueue("data: Hello, world!\n\n\n");
+            }, 1000);
+
+            request.signal.onabort = () => {
+                clearInterval(interval);
+            };
+        },
+    });
+
+    return new Response(stream, {
+        headers: {
+            "Content-Type": "text/event-stream",
+        },
+    });
+}
+```

packages/kit/src/exports/node/index.js

@@ -120,11 +120,19 @@ export async function getRequest({ request, base, bodySizeLimit }) {
 		delete headers[':scheme'];
 	}
 
+	const controller = new AbortController();
+	request.once('close', () => {
+		if (request.readableAborted) {
+			controller.abort();
+		}
+	});
+
 	return new Request(base + request.url, {
 		// @ts-expect-error
 		duplex: 'half',
 		method: request.method,
 		headers: Object.entries(headers),
+		signal: controller.signal,
 		body:
 			request.method === 'GET' || request.method === 'HEAD'
 				? undefined