Add generic type parameter to HTTPError

Closes sindresorhus#615

readme.md

@@ -625,6 +625,8 @@ try {
 }
 ```
 
+⌨️ **TypeScript:** Accepts an optional [type parameter](https://www.typescriptlang.org/docs/handbook/2/generics.html), which defaults to [`unknown`](https://www.typescriptlang.org/docs/handbook/2/functions.html#unknown), and is passed through to the return type of `error.response.json()`.
+
 ### TimeoutError
 
 The error thrown when the request times out. It has a `request` property with the [`Request` object](https://developer.mozilla.org/en-US/docs/Web/API/Request).

source/errors/HTTPError.ts

@@ -2,9 +2,8 @@ import type {NormalizedOptions} from '../types/options.js';
 import type {KyRequest} from '../types/request.js';
 import type {KyResponse} from '../types/response.js';
 
-// eslint-lint-disable-next-line @typescript-eslint/naming-convention
-export class HTTPError extends Error {
-	public response: KyResponse;
+export class HTTPError<T = unknown> extends Error {
+	public response: KyResponse<T>;
 	public request: KyRequest;
 	public options: NormalizedOptions;
 

test/http-error.ts

@@ -1,4 +1,5 @@
 import test from 'ava';
+import {expectTypeOf} from 'expect-type';
 import {HTTPError} from '../source/index.js';
 import {type Mutable} from '../source/utils/types.js';
 
@@ -14,7 +15,7 @@ function createFakeResponse({status, statusText}: {status?: number; statusText?:
 
 test('HTTPError handles undefined response.statusText', t => {
 	const status = 500;
-	// @ts-expect-error missing Request
+	// @ts-expect-error missing options
 	const error = new HTTPError(
 		// This simulates the case where a browser Response object does
 		// not define statusText, such as IE, Safari, etc.
@@ -27,7 +28,7 @@ test('HTTPError handles undefined response.statusText', t => {
 });
 
 test('HTTPError handles undefined response.status', t => {
-	// @ts-expect-error missing Request
+	// @ts-expect-error missing options
 	const error = new HTTPError(
 		// This simulates a catastrophic case where some unexpected
 		// response object was sent to HTTPError.
@@ -39,7 +40,7 @@ test('HTTPError handles undefined response.status', t => {
 });
 
 test('HTTPError handles a response.status of 0', t => {
-	// @ts-expect-error missing Request
+	// @ts-expect-error missing options
 	const error = new HTTPError(
 		// Apparently, it's possible to get a response status of 0.
 		createFakeResponse({statusText: undefined, status: 0}),
@@ -48,3 +49,18 @@ test('HTTPError handles a response.status of 0', t => {
 
 	t.is(error.message, 'Request failed with status code 0: GET invalid:foo');
 });
+
+test('HTTPError provides response.json()', async t => {
+	// @ts-expect-error missing options
+	const error = new HTTPError<{foo: 'bar'}>(
+		new Response(JSON.stringify({foo: 'bar'})),
+		new Request('invalid:foo'),
+	);
+
+	const responseJson = await error.response.json();
+
+	expectTypeOf(responseJson).toEqualTypeOf<{foo: 'bar'}>();
+
+	t.true(error.response instanceof Response);
+	t.deepEqual(responseJson, {foo: 'bar'});
+});