feat(listener): support custom error handler (#131)

* feat(listener): support custom error handler

Signed-off-by: Marc MacLeod <847542+marbemac@users.noreply.github.com>

* pr feedback

Signed-off-by: Marc MacLeod <847542+marbemac@users.noreply.github.com>

* add tests for custom error handling

Signed-off-by: Marc MacLeod <847542+marbemac@users.noreply.github.com>

* format

Signed-off-by: Marc MacLeod <847542+marbemac@users.noreply.github.com>

* lint fix

Signed-off-by: Marc MacLeod <847542+marbemac@users.noreply.github.com>

---------

Signed-off-by: Marc MacLeod <847542+marbemac@users.noreply.github.com>

src/listener.ts

@@ -2,7 +2,7 @@ import type { IncomingMessage, ServerResponse, OutgoingHttpHeaders } from 'node:
 import type { Http2ServerRequest, Http2ServerResponse } from 'node:http2'
 import { newRequest } from './request'
 import { cacheKey } from './response'
-import type { FetchCallback, HttpBindings } from './types'
+import type { CustomErrorHandler, FetchCallback, HttpBindings } from './types'
 import { writeFromReadableStream, buildOutgoingHttpHeaders } from './utils'
 import './globals'
 
@@ -53,9 +53,24 @@ const responseViaCache = (
 
 const responseViaResponseObject = async (
  res: Response | Promise<Response>,
- outgoing: ServerResponse | Http2ServerResponse
+ outgoing: ServerResponse | Http2ServerResponse,
+ options: { errorHandler?: CustomErrorHandler } = {}
 ) => {
- res = res instanceof Promise ? await res.catch(handleFetchError) : res
+ if (res instanceof Promise) {
+ if (options.errorHandler) {
+ try {
+ res = await res
+ } catch (err) {
+ const errRes = await options.errorHandler(err)
+ if (!errRes) {
+ return
+ }
+ res = errRes
+ }
+ } else {
+ res = await res.catch(handleFetchError)
+ }
+ }
 
  try {
  const isCached = cacheKey in res
@@ -114,8 +129,11 @@ const responseViaResponseObject = async (
  }
 }
 
-export const getRequestListener = (fetchCallback: FetchCallback) => {
- return (
+export const getRequestListener = (
+ fetchCallback: FetchCallback,
+ options: { errorHandler?: CustomErrorHandler } = {}
+) => {
+ return async (
  incoming: IncomingMessage | Http2ServerRequest,
  outgoing: ServerResponse | Http2ServerResponse
  ) => {
@@ -135,12 +153,19 @@ export const getRequestListener = (fetchCallback: FetchCallback) => {
  }
  } catch (e: unknown) {
  if (!res) {
- res = handleFetchError(e)
+ if (options.errorHandler) {
+ res = await options.errorHandler(e)
+ if (!res) {
+ return
+ }
+ } else {
+ res = handleFetchError(e)
+ }
  } else {
  return handleResponseError(e, outgoing)
  }
  }
 
- return responseViaResponseObject(res, outgoing)
+ return responseViaResponseObject(res, outgoing, options)
  }
 }

src/types.ts

@@ -72,3 +72,5 @@ export type Options = {
  port?: number
  hostname?: string
 } & ServerOptions
+
+export type CustomErrorHandler = (err: unknown) => void | Response | Promise<void | Response>

test/listener.test.ts

@@ -0,0 +1,91 @@
+import { createServer } from 'node:http'
+import request from 'supertest'
+import { getRequestListener } from '../src/listener'
+
+describe('Error handling - sync fetchCallback', () => {
+ const fetchCallback = jest.fn(() => {
+ throw new Error('thrown error')
+ })
+ const errorHandler = jest.fn()
+
+ const requestListener = getRequestListener(fetchCallback, { errorHandler })
+
+ const server = createServer(async (req, res) => {
+ await requestListener(req, res)
+
+ if (!res.writableEnded) {
+ res.writeHead(500, { 'Content-Type': 'text/plain' })
+ res.end('error handler did not return a response')
+ }
+ })
+
+ beforeEach(() => {
+ errorHandler.mockReset()
+ })
+
+ it('Should set the response if error handler returns a response', async () => {
+ errorHandler.mockImplementationOnce((err: Error) => {
+ return new Response(`${err}`, { status: 500, headers: { 'my-custom-header': 'hi' } })
+ })
+
+ const res = await request(server).get('/throw-error')
+ expect(res.status).toBe(500)
+ expect(res.headers['my-custom-header']).toBe('hi')
+ expect(res.text).toBe('Error: thrown error')
+ })
+
+ it('Should not set the response if the error handler does not return a response', async () => {
+ errorHandler.mockImplementationOnce(() => {
+ // do something else, such as passing error to vite next middleware, etc
+ })
+
+ const res = await request(server).get('/throw-error')
+ expect(errorHandler).toHaveBeenCalledTimes(1)
+ expect(res.status).toBe(500)
+ expect(res.text).toBe('error handler did not return a response')
+ })
+})
+
+describe('Error handling - async fetchCallback', () => {
+ const fetchCallback = jest.fn(async () => {
+ throw new Error('thrown error')
+ })
+ const errorHandler = jest.fn()
+
+ const requestListener = getRequestListener(fetchCallback, { errorHandler })
+
+ const server = createServer(async (req, res) => {
+ await requestListener(req, res)
+
+ if (!res.writableEnded) {
+ res.writeHead(500, { 'Content-Type': 'text/plain' })
+ res.end('error handler did not return a response')
+ }
+ })
+
+ beforeEach(() => {
+ errorHandler.mockReset()
+ })
+
+ it('Should set the response if error handler returns a response', async () => {
+ errorHandler.mockImplementationOnce((err: Error) => {
+ return new Response(`${err}`, { status: 500, headers: { 'my-custom-header': 'hi' } })
+ })
+
+ const res = await request(server).get('/throw-error')
+ expect(res.status).toBe(500)
+ expect(res.headers['my-custom-header']).toBe('hi')
+ expect(res.text).toBe('Error: thrown error')
+ })
+
+ it('Should not set the response if the error handler does not return a response', async () => {
+ errorHandler.mockImplementationOnce(() => {
+ // do something else, such as passing error to vite next middleware, etc
+ })
+
+ const res = await request(server).get('/throw-error')
+ expect(errorHandler).toHaveBeenCalledTimes(1)
+ expect(res.status).toBe(500)
+ expect(res.text).toBe('error handler did not return a response')
+ })
+})