Add beforeError hook (#417)

Co-authored-by: Sindre Sorhus <sindresorhus@gmail.com>

Author: Malolan B

readme.md

@@ -258,6 +258,33 @@ const response = await ky('https://example.com', {
 });
 ```
 
+###### hooks.beforeError
+
+Type: `Function[]`\
+Default: `[]`
+
+This hook enables you to modify the `HTTPError` right before it is thrown. The hook function receives a `HTTPError` as an argument and should return an instance of `HTTPError`.
+
+```js
+import ky from 'ky';
+
+await ky('https://example.com', {
+	hooks: {
+		beforeError: [
+			error => {
+				const {response} = error;
+				if (response && response.body) {
+					error.name = 'GitHubError';
+					error.message = `${response.body.message} (${response.statusCode})`;
+				}
+
+				return error;
+			}
+		]
+	}
+});
+```
+
 ###### hooks.afterResponse
 
 Type: `Function[]`\

source/core/Ky.ts

@@ -39,7 +39,14 @@ export class Ky {
 			ky._decorateResponse(response);
 
 			if (!response.ok && ky._options.throwHttpErrors) {
-				throw new HTTPError(response, ky.request, (ky._options as unknown) as NormalizedOptions);
+				let error = new HTTPError(response, ky.request, (ky._options as unknown) as NormalizedOptions);
+
+				for (const hook of ky._options.hooks.beforeError) {
+					// eslint-disable-next-line no-await-in-loop
+					error = await hook(error);
+				}
+
+				throw error;
 			}
 
 			// If `onDownloadProgress` is passed, it uses the stream API internally
@@ -104,6 +111,7 @@ export class Ky {
 				{
 					beforeRequest: [],
 					beforeRetry: [],
+					beforeError: [],
 					afterResponse: [],
 				},
 				options.hooks,

source/index.ts

@@ -39,6 +39,7 @@ export {
 	Hooks,
 	BeforeRequestHook,
 	BeforeRetryHook,
+	BeforeErrorHook,
 	AfterResponseHook,
 } from './types/hooks.js';
 

source/types/hooks.ts

@@ -1,4 +1,5 @@
 import {stop} from '../core/constants.js';
+import {HTTPError} from '../index.js';
 import type {NormalizedOptions} from './options.js';
 
 export type BeforeRequestHook = (
@@ -20,6 +21,8 @@ export type AfterResponseHook = (
 	response: Response
 ) => Response | void | Promise<Response | void>;
 
+export type BeforeErrorHook = (error: HTTPError) => HTTPError | Promise<HTTPError>;
+
 export interface Hooks {
 	/**
 	This hook enables you to modify the request right before it is sent. Ky will make no further changes to the request after this. The hook function receives normalized input and options as arguments. You could, forf example, modiy `options.headers` here.
@@ -95,4 +98,32 @@ export interface Hooks {
 	```
 	*/
 	afterResponse?: AfterResponseHook[];
+
+	/**
+	This hook enables you to modify the `HTTPError` right before it is thrown. The hook function receives a `HTTPError` as an argument and should return an instance of `HTTPError`.
+
+	@default []
+
+	@example
+	```
+	import ky from 'ky';
+
+	await ky('https://example.com', {
+		hooks: {
+			beforeError: [
+				error => {
+					const {response} = error;
+					if (response && response.body) {
+						error.name = 'GitHubError';
+						error.message = `${response.body.message} (${response.statusCode})`;
+					}
+
+					return error;
+				}
+			]
+		}
+	});
+	```
+	*/
+	beforeError?: BeforeErrorHook[];
 }

test/helpers/with-page.ts

@@ -1,5 +1,4 @@
 import process from 'node:process';
-// eslint-disable-next-line ava/use-test
 import type {ExecutionContext, UntitledMacro} from 'ava';
 import {chromium, Page} from 'playwright-chromium';
 

test/hooks.ts

@@ -602,3 +602,69 @@ test('hooks beforeRequest returning Response skips HTTP Request', async t => {
 
 	t.is(response, expectedResponse);
 });
+
+test('runs beforeError before throwing HTTPError', async t => {
+	const server = await createHttpTestServer();
+	server.post('/', (_request, response) => {
+		response.status(500).send();
+	});
+
+	await t.throwsAsync(
+		ky.post(server.url, {
+			hooks: {
+				beforeError: [
+					(error: HTTPError) => {
+						const {response} = error;
+
+						if (response?.body) {
+							error.name = 'GitHubError';
+							error.message = `${response.statusText} --- (${response.status})`.trim();
+						}
+
+						return error;
+					},
+				],
+			},
+		}),
+		{
+			name: 'GitHubError',
+			message: 'Internal Server Error --- (500)',
+		},
+	);
+
+	await server.close();
+});
+
+test('beforeError can return promise which resolves to HTTPError', async t => {
+	const server = await createHttpTestServer();
+	const responseBody = {reason: 'github down'};
+	server.post('/', (_request, response) => {
+		response.status(500).send(responseBody);
+	});
+
+	await t.throwsAsync(
+		ky.post(server.url, {
+			hooks: {
+				beforeError: [
+					async (error: HTTPError) => {
+						const {response} = error;
+						const body = await response.json() as {reason: string};
+
+						if (response?.body) {
+							error.name = 'GitHubError';
+							error.message = `${body.reason} --- (${response.status})`.trim();
+						}
+
+						return error;
+					},
+				],
+			},
+		}),
+		{
+			name: 'GitHubError',
+			message: `${responseBody.reason} --- (500)`,
+		},
+	);
+
+	await server.close();
+});