Fix signal handling for Request objects (#613)

* Fix signal handling for Request objects

Fix lint issues

* Simplify signal handling

* Fix lint error

* Add a test for aborting via a Request object

---------

Co-authored-by: Seth Holladay <me@seth-holladay.com>

source/core/Ky.ts

@@ -168,13 +168,10 @@ export class Ky {
 
 		if (supportsAbortController) {
 			this.abortController = new globalThis.AbortController();
-			if (this._options.signal) {
-				const originalSignal = this._options.signal;
-
-				this._options.signal.addEventListener('abort', () => {
-					this.abortController!.abort(originalSignal.reason);
-				});
-			}
+			const originalSignal = this._options.signal ?? (this._input as Request).signal;
+			originalSignal?.addEventListener('abort', () => {
+				this.abortController!.abort(originalSignal.reason);
+			});
 
 			this._options.signal = this.abortController.signal;
 		}

test/main.ts

@@ -711,6 +711,23 @@ test('throws DOMException/Error with name AbortError when aborted by user', asyn
 	t.is(error.name, 'AbortError', `Expected AbortError, got ${error.name}`);
 });
 
+test('throws AbortError when aborted via Request', async t => {
+	const server = await createHttpTestServer();
+	// eslint-disable-next-line @typescript-eslint/no-empty-function
+	server.get('/', () => {});
+
+	const abortController = new AbortController();
+	const {signal} = abortController;
+	const request = new Request(server.url, {signal});
+	const response = ky(request);
+	abortController.abort();
+
+	const error = (await t.throwsAsync(response))!;
+
+	t.true(['DOMException', 'Error'].includes(error.constructor.name), `Expected DOMException or Error, got ${error.constructor.name}`);
+	t.is(error.name, 'AbortError', `Expected AbortError, got ${error.name}`);
+});
+
 test('supports Request instance as input', async t => {
 	const server = await createHttpTestServer();
 	const inputRequest = new Request(server.url, {method: 'POST'});