[node-bridge] Move helpers to node-bridge (#7451)

.eslintignore

@@ -14,4 +14,6 @@ packages/client/lib
 packages/node/src/bridge.ts
 packages/node-bridge/bridge.js
 packages/node-bridge/launcher.js
+packages/node-bridge/helpers.js
+packages/node-bridge/source-map-support.js
 packages/middleware/src/entries.js

packages/node-bridge/.gitignore

@@ -0,0 +1,2 @@
+/helpers.js
+/source-map-support.js

packages/node-bridge/build.js

@@ -0,0 +1,62 @@
+#!/usr/bin/env node
+const fs = require('fs-extra');
+const execa = require('execa');
+const { join } = require('path');
+
+async function main() {
+  // Build TypeScript files
+  await execa('tsc', [], {
+    stdio: 'inherit',
+  });
+
+  // Bundle `helpers.ts` with ncc
+  await fs.remove(join(__dirname, 'helpers.js'));
+  const helpersDir = join(__dirname, 'helpers');
+  await execa(
+    'ncc',
+    [
+      'build',
+      join(__dirname, 'helpers.ts'),
+      '-e',
+      '@vercel/node-bridge',
+      '-e',
+      '@vercel/build-utils',
+      '-e',
+      'typescript',
+      '-o',
+      helpersDir,
+    ],
+    { stdio: 'inherit' }
+  );
+  await fs.rename(join(helpersDir, 'index.js'), join(__dirname, 'helpers.js'));
+  await fs.remove(helpersDir);
+
+  // Bundle `source-map-support/register` with ncc for source maps
+  const sourceMapSupportDir = join(__dirname, 'source-map-support');
+  await execa(
+    'ncc',
+    [
+      'build',
+      join(__dirname, '../../node_modules/source-map-support/register'),
+      '-e',
+      '@vercel/node-bridge',
+      '-e',
+      '@vercel/build-utils',
+      '-e',
+      'typescript',
+      '-o',
+      sourceMapSupportDir,
+    ],
+    { stdio: 'inherit' }
+  );
+  await fs.rename(
+    join(sourceMapSupportDir, 'index.js'),
+    join(__dirname, 'source-map-support.js')
+  );
+  await fs.remove(sourceMapSupportDir);
+}
+
+main().catch(err => {
+  console.error(err);
+  process.exit(1);
+});

packages/node-bridge/helpers.ts

@@ -0,0 +1,309 @@
+import type {
+  VercelRequest,
+  VercelResponse,
+  VercelRequestCookies,
+  VercelRequestQuery,
+  VercelRequestBody,
+} from './types';
+import { Server } from 'http';
+import type { Bridge } from './bridge';
+
+function getBodyParser(req: VercelRequest, body: Buffer) {
+  return function parseBody(): VercelRequestBody {
+    if (!req.headers['content-type']) {
+      return undefined;
+    }
+    // eslint-disable-next-line @typescript-eslint/no-var-requires
+    const { parse: parseContentType } = require('content-type');
+    const { type } = parseContentType(req.headers['content-type']);
+
+    if (type === 'application/json') {
+      try {
+        const str = body.toString();
+        return str ? JSON.parse(str) : {};
+      } catch (error) {
+        throw new ApiError(400, 'Invalid JSON');
+      }
+    }
+
+    if (type === 'application/octet-stream') {
+      return body;
+    }
+
+    if (type === 'application/x-www-form-urlencoded') {
+      // eslint-disable-next-line @typescript-eslint/no-var-requires
+      const { parse: parseQS } = require('querystring');
+      // note: querystring.parse does not produce an iterable object
+      // https://nodejs.org/api/querystring.html#querystring_querystring_parse_str_sep_eq_options
+      return parseQS(body.toString());
+    }
+
+    if (type === 'text/plain') {
+      return body.toString();
+    }
+
+    return undefined;
+  };
+}
+
+function getQueryParser({ url = '/' }: VercelRequest) {
+  return function parseQuery(): VercelRequestQuery {
+    // eslint-disable-next-line @typescript-eslint/no-var-requires
+    const { parse: parseURL } = require('url');
+    return parseURL(url, true).query;
+  };
+}
+
+function getCookieParser(req: VercelRequest) {
+  return function parseCookie(): VercelRequestCookies {
+    const header: undefined | string | string[] = req.headers.cookie;
+
+    if (!header) {
+      return {};
+    }
+
+    // eslint-disable-next-line @typescript-eslint/no-var-requires
+    const { parse } = require('cookie');
+    return parse(Array.isArray(header) ? header.join(';') : header);
+  };
+}
+
+function status(res: VercelResponse, statusCode: number): VercelResponse {
+  res.statusCode = statusCode;
+  return res;
+}
+
+function redirect(
+  res: VercelResponse,
+  statusOrUrl: string | number,
+  url?: string
+): VercelResponse {
+  if (typeof statusOrUrl === 'string') {
+    url = statusOrUrl;
+    statusOrUrl = 307;
+  }
+  if (typeof statusOrUrl !== 'number' || typeof url !== 'string') {
+    throw new Error(
+      `Invalid redirect arguments. Please use a single argument URL, e.g. res.redirect('/destination') or use a status code and URL, e.g. res.redirect(307, '/destination').`
+    );
+  }
+  res.writeHead(statusOrUrl, { Location: url }).end();
+  return res;
+}
+
+function setCharset(type: string, charset: string) {
+  // eslint-disable-next-line @typescript-eslint/no-var-requires
+  const { parse, format } = require('content-type');
+  const parsed = parse(type);
+  parsed.parameters.charset = charset;
+  return format(parsed);
+}
+
+// eslint-disable-next-line @typescript-eslint/no-explicit-any
+function createETag(body: any, encoding: 'utf8' | undefined) {
+  // eslint-disable-next-line @typescript-eslint/no-var-requires
+  const etag = require('etag');
+  const buf = !Buffer.isBuffer(body) ? Buffer.from(body, encoding) : body;
+  return etag(buf, { weak: true });
+}
+
+// eslint-disable-next-line @typescript-eslint/no-explicit-any
+function send(
+  req: VercelRequest,
+  res: VercelResponse,
+  body: any
+): VercelResponse {
+  let chunk: unknown = body;
+  let encoding: 'utf8' | undefined;
+
+  switch (typeof chunk) {
+    // string defaulting to html
+    case 'string':
+      if (!res.getHeader('content-type')) {
+        res.setHeader('content-type', 'text/html');
+      }
+      break;
+    case 'boolean':
+    case 'number':
+    case 'object':
+      if (chunk === null) {
+        chunk = '';
+      } else if (Buffer.isBuffer(chunk)) {
+        if (!res.getHeader('content-type')) {
+          res.setHeader('content-type', 'application/octet-stream');
+        }
+      } else {
+        return json(req, res, chunk);
+      }
+      break;
+  }
+
+  // write strings in utf-8
+  if (typeof chunk === 'string') {
+    encoding = 'utf8';
+
+    // reflect this in content-type
+    const type = res.getHeader('content-type');
+    if (typeof type === 'string') {
+      res.setHeader('content-type', setCharset(type, 'utf-8'));
+    }
+  }
+
+  // populate Content-Length
+  let len: number | undefined;
+  if (chunk !== undefined) {
+    if (Buffer.isBuffer(chunk)) {
+      // get length of Buffer
+      len = chunk.length;
+    } else if (typeof chunk === 'string') {
+      if (chunk.length < 1000) {
+        // just calculate length small chunk
+        len = Buffer.byteLength(chunk, encoding);
+      } else {
+        // convert chunk to Buffer and calculate
+        const buf = Buffer.from(chunk, encoding);
+        len = buf.length;
+        chunk = buf;
+        encoding = undefined;
+      }
+    } else {
+      throw new Error(
+        '`body` is not a valid string, object, boolean, number, Stream, or Buffer'
+      );
+    }
+
+    if (len !== undefined) {
+      res.setHeader('content-length', len);
+    }
+  }
+
+  // populate ETag
+  let etag: string | undefined;
+  if (
+    !res.getHeader('etag') &&
+    len !== undefined &&
+    (etag = createETag(chunk, encoding))
+  ) {
+    res.setHeader('etag', etag);
+  }
+
+  // strip irrelevant headers
+  if (204 === res.statusCode || 304 === res.statusCode) {
+    res.removeHeader('Content-Type');
+    res.removeHeader('Content-Length');
+    res.removeHeader('Transfer-Encoding');
+    chunk = '';
+  }
+
+  if (req.method === 'HEAD') {
+    // skip body for HEAD
+    res.end();
+  } else if (encoding) {
+    // respond with encoding
+    res.end(chunk, encoding);
+  } else {
+    // respond without encoding
+    res.end(chunk);
+  }
+
+  return res;
+}
+
+// eslint-disable-next-line @typescript-eslint/no-explicit-any
+function json(
+  req: VercelRequest,
+  res: VercelResponse,
+  jsonBody: any
+): VercelResponse {
+  const body = JSON.stringify(jsonBody);
+
+  // content-type
+  if (!res.getHeader('content-type')) {
+    res.setHeader('content-type', 'application/json; charset=utf-8');
+  }
+
+  return send(req, res, body);
+}
+
+export class ApiError extends Error {
+  readonly statusCode: number;
+
+  constructor(statusCode: number, message: string) {
+    super(message);
+    this.statusCode = statusCode;
+  }
+}
+
+export function sendError(
+  res: VercelResponse,
+  statusCode: number,
+  message: string
+) {
+  res.statusCode = statusCode;
+  res.statusMessage = message;
+  res.end();
+}
+
+function setLazyProp<T>(req: VercelRequest, prop: string, getter: () => T) {
+  const opts = { configurable: true, enumerable: true };
+  const optsReset = { ...opts, writable: true };
+
+  Object.defineProperty(req, prop, {
+    ...opts,
+    get: () => {
+      const value = getter();
+      // we set the property on the object to avoid recalculating it
+      Object.defineProperty(req, prop, { ...optsReset, value });
+      return value;
+    },
+    set: value => {
+      Object.defineProperty(req, prop, { ...optsReset, value });
+    },
+  });
+}
+
+export function createServerWithHelpers(
+  handler: (req: VercelRequest, res: VercelResponse) => void | Promise<void>,
+  bridge: Bridge
+) {
+  const server = new Server(async (_req, _res) => {
+    const req = _req as VercelRequest;
+    const res = _res as VercelResponse;
+
+    try {
+      const reqId = req.headers['x-now-bridge-request-id'];
+
+      // don't expose this header to the client
+      delete req.headers['x-now-bridge-request-id'];
+
+      if (typeof reqId !== 'string') {
+        throw new ApiError(500, 'Internal Server Error');
+      }
+
+      const event = bridge.consumeEvent(reqId);
+
+      setLazyProp<VercelRequestCookies>(req, 'cookies', getCookieParser(req));
+      setLazyProp<VercelRequestQuery>(req, 'query', getQueryParser(req));
+      setLazyProp<VercelRequestBody>(
+        req,
+        'body',
+        getBodyParser(req, event.body)
+      );
+
+      res.status = statusCode => status(res, statusCode);
+      res.redirect = (statusOrUrl, url) => redirect(res, statusOrUrl, url);
+      res.send = body => send(req, res, body);
+      res.json = jsonBody => json(req, res, jsonBody);
+
+      await handler(req, res);
+    } catch (err) {
+      if (err instanceof ApiError) {
+        sendError(res, err.statusCode, err.message);
+      } else {
+        throw err;
+      }
+    }
+  });
+
+  return server;
+}

packages/node-bridge/package.json

@@ -11,10 +11,12 @@
   "files": [
     "bridge.*",
     "launcher.*",
-    "index.js"
+    "index.js",
+    "helpers.js",
+    "source-map-support.js"
   ],
   "scripts": {
-    "build": "tsc",
+    "build": "node build.js",
     "test-unit": "jest --env node --verbose --runInBand --bail"
   },
   "devDependencies": {

packages/node-bridge/test/helpers.test.js

@@ -0,0 +1,842 @@
+const fetch = require('node-fetch');
+const listen = require('test-listen');
+const qs = require('querystring');
+
+const { createServerWithHelpers } = require('../helpers');
+
+const mockListener = jest.fn();
+const consumeEventMock = jest.fn();
+const mockBridge = { consumeEvent: consumeEventMock };
+
+let server;
+let url;
+
+async function fetchWithProxyReq(_url, opts = {}) {
+  if (opts.body) {
+    // eslint-disable-next-line
+    opts = { ...opts, body: Buffer.from(opts.body) };
+  }
+
+  consumeEventMock.mockImplementationOnce(() => opts);
+
+  return fetch(_url, {
+    ...opts,
+    headers: { ...opts.headers, 'x-now-bridge-request-id': '2' },
+  });
+}
+
+beforeEach(async () => {
+  mockListener.mockClear();
+  consumeEventMock.mockClear();
+
+  mockListener.mockImplementation((req, res) => {
+    res.send('hello');
+  });
+  consumeEventMock.mockImplementation(() => ({}));
+
+  server = createServerWithHelpers(mockListener, mockBridge);
+  url = await listen(server);
+});
+
+afterEach(async () => {
+  await server.close();
+});
+
+describe('contract with @vercel/node-bridge', () => {
+  test('should call consumeEvent with the correct reqId', async () => {
+    await fetchWithProxyReq(`${url}/`);
+
+    expect(consumeEventMock).toHaveBeenLastCalledWith('2');
+  });
+
+  test('should not expose the request id header', async () => {
+    await fetchWithProxyReq(`${url}/`, { headers: { 'x-test-header': 'ok' } });
+
+    const [{ headers }] = mockListener.mock.calls[0];
+
+    expect(headers['x-now-bridge-request-id']).toBeUndefined();
+    expect(headers['x-test-header']).toBe('ok');
+  });
+});
+
+describe('all helpers', () => {
+  const nowHelpers = [
+    ['query', 0],
+    ['cookies', 0],
+    ['body', 0],
+    ['status', 1],
+    ['redirect', 1],
+    ['send', 1],
+    ['json', 1],
+  ];
+
+  test('should not recalculate req properties twice', async () => {
+    const spy = jest.fn(() => {});
+
+    const nowReqHelpers = nowHelpers.filter(([, i]) => i === 0);
+
+    mockListener.mockImplementation((req, res) => {
+      spy(...nowReqHelpers.map(h => req[h]));
+      spy(...nowReqHelpers.map(h => req[h]));
+      res.end();
+    });
+
+    await fetchWithProxyReq(`${url}/?who=bill`, {
+      method: 'POST',
+      body: JSON.stringify({ who: 'mike' }),
+      headers: { 'content-type': 'application/json', cookie: 'who=jim' },
+    });
+
+    // here we test that bodySpy is called twice with exactly the same arguments
+    for (let i = 0; i < 3; i += 1) {
+      expect(spy.mock.calls[0][i]).toBe(spy.mock.calls[1][i]);
+    }
+  });
+
+  test('should be able to overwrite request properties', async () => {
+    const spy = jest.fn(() => {});
+
+    mockListener.mockImplementation((...args) => {
+      nowHelpers.forEach(([prop, n]) => {
+        /* eslint-disable */
+        args[n][prop] = 'ok';
+        args[n][prop] = 'ok2';
+        spy(args[n][prop]);
+      });
+
+      args[1].end();
+    });
+
+    await fetchWithProxyReq(url);
+
+    nowHelpers.forEach((_, i) => expect(spy.mock.calls[i][0]).toBe('ok2'));
+  });
+
+  test('should be able to reconfig request properties', async () => {
+    const spy = jest.fn(() => {});
+
+    mockListener.mockImplementation((...args) => {
+      nowHelpers.forEach(([prop, n]) => {
+        // eslint-disable-next-line
+        Object.defineProperty(args[n], prop, { value: 'ok' });
+        Object.defineProperty(args[n], prop, { value: 'ok2' });
+        spy(args[n][prop]);
+      });
+
+      args[1].end();
+    });
+
+    await fetchWithProxyReq(url);
+
+    nowHelpers.forEach((_, i) => expect(spy.mock.calls[i][0]).toBe('ok2'));
+  });
+});
+
+describe('req.query', () => {
+  test('req.query should reflect querystring in the url', async () => {
+    await fetchWithProxyReq(`${url}/?who=bill&where=us`);
+
+    expect(mockListener.mock.calls[0][0].query).toMatchObject({
+      who: 'bill',
+      where: 'us',
+    });
+  });
+
+  test('req.query should turn multiple params with same name into an array', async () => {
+    await fetchWithProxyReq(`${url}/?a=2&a=1`);
+
+    expect(mockListener.mock.calls[0][0].query).toMatchObject({
+      a: ['2', '1'],
+    });
+  });
+
+  test('req.query should be {} when there is no querystring', async () => {
+    await fetchWithProxyReq(url);
+    const [{ query }] = mockListener.mock.calls[0];
+    expect(Object.keys(query).length).toBe(0);
+  });
+});
+
+describe('req.cookies', () => {
+  test('req.cookies should reflect req.cookie header', async () => {
+    await fetchWithProxyReq(url, {
+      headers: {
+        cookie: 'who=bill; where=us',
+      },
+    });
+
+    expect(mockListener.mock.calls[0][0].cookies).toMatchObject({
+      who: 'bill',
+      where: 'us',
+    });
+  });
+});
+
+describe('req.body', () => {
+  test('req.body should be undefined by default', async () => {
+    await fetchWithProxyReq(url);
+    expect(mockListener.mock.calls[0][0].body).toBe(undefined);
+  });
+
+  test('req.body should be undefined if content-type is not defined', async () => {
+    await fetchWithProxyReq(url, {
+      method: 'POST',
+      body: 'hello',
+    });
+    expect(mockListener.mock.calls[0][0].body).toBe(undefined);
+  });
+
+  test('req.body should be a string when content-type is `text/plain`', async () => {
+    await fetchWithProxyReq(url, {
+      method: 'POST',
+      body: 'hello',
+      headers: { 'content-type': 'text/plain' },
+    });
+
+    expect(mockListener.mock.calls[0][0].body).toBe('hello');
+  });
+
+  test('req.body should be a buffer when content-type is `application/octet-stream`', async () => {
+    await fetchWithProxyReq(url, {
+      method: 'POST',
+      body: 'hello',
+      headers: { 'content-type': 'application/octet-stream' },
+    });
+
+    const [{ body }] = mockListener.mock.calls[0];
+
+    const str = body.toString();
+
+    expect(Buffer.isBuffer(body)).toBe(true);
+    expect(str).toBe('hello');
+  });
+
+  test('req.body should be an object when content-type is `application/x-www-form-urlencoded`', async () => {
+    const obj = { who: 'mike' };
+
+    await fetchWithProxyReq(url, {
+      method: 'POST',
+      body: qs.encode(obj),
+      headers: { 'content-type': 'application/x-www-form-urlencoded' },
+    });
+
+    expect(mockListener.mock.calls[0][0].body).toMatchObject(obj);
+  });
+
+  test('req.body should be an object when content-type is `application/json`', async () => {
+    const json = {
+      who: 'bill',
+      where: 'us',
+    };
+
+    await fetchWithProxyReq(url, {
+      method: 'POST',
+      body: JSON.stringify(json),
+      headers: { 'content-type': 'application/json' },
+    });
+
+    expect(mockListener.mock.calls[0][0].body).toMatchObject(json);
+  });
+
+  test('should work when body is empty and content-type is `application/json`', async () => {
+    mockListener.mockImplementation((req, res) => {
+      console.log(req.body);
+      res.end();
+    });
+
+    const res = await fetchWithProxyReq(url, {
+      method: 'POST',
+      body: '',
+      headers: { 'content-type': 'application/json' },
+    });
+
+    expect(res.status).toBe(200);
+    expect(res.body).toMatchObject({});
+  });
+
+  test('should be able to try/catch parse errors', async () => {
+    const bodySpy = jest.fn(() => {});
+
+    mockListener.mockImplementation((req, res) => {
+      try {
+        if (req.body === undefined) res.status(400);
+      } catch (error) {
+        bodySpy(error);
+      } finally {
+        res.end();
+      }
+    });
+
+    await fetchWithProxyReq(url, {
+      method: 'POST',
+      body: '{"wrong":"json"',
+      headers: { 'content-type': 'application/json' },
+    });
+
+    expect(bodySpy).toHaveBeenCalled();
+
+    const [error] = bodySpy.mock.calls[0];
+    expect(error.message).toMatch(/invalid json/i);
+    expect(error.statusCode).toBe(400);
+  });
+});
+
+describe('res.status', () => {
+  test('res.status() should set the status code', async () => {
+    mockListener.mockImplementation((req, res) => {
+      res.status(404);
+      res.end();
+    });
+
+    const res = await fetchWithProxyReq(url);
+
+    expect(res.status).toBe(404);
+  });
+
+  test('res.status() should be chainable', async () => {
+    const spy = jest.fn();
+
+    mockListener.mockImplementation((req, res) => {
+      spy(res, res.status(404));
+      res.end();
+    });
+
+    await fetchWithProxyReq(url);
+
+    const [a, b] = spy.mock.calls[0];
+    expect(a).toBe(b);
+  });
+});
+
+describe('res.redirect', () => {
+  test('should redirect to login', async () => {
+    mockListener.mockImplementation((req, res) => {
+      res.redirect('/login');
+      res.end();
+    });
+
+    const res = await fetchWithProxyReq(url, { redirect: 'manual' });
+
+    expect(res.status).toBe(307);
+    expect(res.headers.get('location')).toBe(url + '/login');
+  });
+  test('should redirect with status code 301', async () => {
+    mockListener.mockImplementation((req, res) => {
+      res.redirect(301, '/login');
+      res.end();
+    });
+    const res = await fetchWithProxyReq(url, { redirect: 'manual' });
+    expect(res.status).toBe(301);
+    expect(res.headers.get('location')).toBe(url + '/login');
+  });
+  test('should show friendly error for invalid redirect', async () => {
+    let error;
+    mockListener.mockImplementation((req, res) => {
+      try {
+        res.redirect(307);
+      } catch (err) {
+        error = err;
+      }
+      res.end();
+    });
+    await fetchWithProxyReq(url, { redirect: 'manual' });
+    expect(error.message).toBe(
+      `Invalid redirect arguments. Please use a single argument URL, e.g. res.redirect('/destination') or use a status code and URL, e.g. res.redirect(307, '/destination').`
+    );
+  });
+  test('should show friendly error in case of passing null as first argument redirect', async () => {
+    let error;
+    mockListener.mockImplementation((req, res) => {
+      try {
+        res.redirect(null);
+      } catch (err) {
+        error = err;
+      }
+      res.end();
+    });
+    await fetchWithProxyReq(url, { redirect: 'manual' });
+    expect(error.message).toBe(
+      `Invalid redirect arguments. Please use a single argument URL, e.g. res.redirect('/destination') or use a status code and URL, e.g. res.redirect(307, '/destination').`
+    );
+  });
+});
+
+// tests based on expressjs test suite
+// see https://github.com/expressjs/express/blob/master/test/res.send.js
+describe('res.send', () => {
+  test('should be chainable', async () => {
+    const spy = jest.fn();
+
+    mockListener.mockImplementation((req, res) => {
+      spy(res, res.send('hello'));
+    });
+
+    await fetchWithProxyReq(url);
+
+    const [a, b] = spy.mock.calls[0];
+    expect(a).toBe(b);
+  });
+
+  describe('res.send()', () => {
+    test('should set body to ""', async () => {
+      mockListener.mockImplementation((req, res) => {
+        res.send();
+      });
+
+      const res = await fetchWithProxyReq(url);
+      expect(res.status).toBe(200);
+      expect(await res.text()).toBe('');
+    });
+  });
+
+  describe('.send(null)', () => {
+    test('should set body to ""', async () => {
+      mockListener.mockImplementation((req, res) => {
+        res.send(null);
+      });
+
+      const res = await fetchWithProxyReq(url);
+      expect(res.status).toBe(200);
+      expect(res.headers.get('content-length')).toBe('0');
+      expect(await res.text()).toBe('');
+    });
+  });
+
+  describe('.send(undefined)', () => {
+    test('should set body to ""', async () => {
+      mockListener.mockImplementation((req, res) => {
+        res.send(undefined);
+      });
+
+      const res = await fetchWithProxyReq(url);
+      expect(res.status).toBe(200);
+      expect(await res.text()).toBe('');
+    });
+  });
+
+  describe('.send(String)', () => {
+    test('should send as html', async () => {
+      mockListener.mockImplementation((req, res) => {
+        res.send('<p>hey</p>');
+      });
+
+      const res = await fetchWithProxyReq(url);
+      expect(res.headers.get('content-type')).toBe('text/html; charset=utf-8');
+      expect(await res.text()).toBe('<p>hey</p>');
+    });
+
+    test('should set Content-Length', async () => {
+      mockListener.mockImplementation((req, res) => {
+        res.send('½ + ¼ = ¾');
+      });
+
+      const res = await fetchWithProxyReq(url);
+      expect(res.status).toBe(200);
+      expect(Number(res.headers.get('content-length'))).toBe(12);
+      expect(await res.text()).toBe('½ + ¼ = ¾');
+    });
+
+    test('should set ETag', async () => {
+      mockListener.mockImplementation((req, res) => {
+        res.send(Array(1000).join('-'));
+      });
+
+      const res = await fetchWithProxyReq(url);
+      expect(res.status).toBe(200);
+      expect(res.headers.get('ETag')).toBe(
+        'W/"3e7-qPnkJ3CVdVhFJQvUBfF10TmVA7g"'
+      );
+    });
+
+    test('should not override Content-Type', async () => {
+      mockListener.mockImplementation((req, res) => {
+        res.setHeader('Content-Type', 'text/plain');
+        res.send('hey');
+      });
+
+      const res = await fetchWithProxyReq(url);
+      expect(res.status).toBe(200);
+      expect(res.headers.get('Content-Type')).toBe('text/plain; charset=utf-8');
+      expect(await res.text()).toBe('hey');
+    });
+
+    test('should override charset in Content-Type', async () => {
+      mockListener.mockImplementation((req, res) => {
+        res.setHeader('Content-Type', 'text/plain; charset=iso-8859-1');
+        res.send('hey');
+      });
+
+      const res = await fetchWithProxyReq(url);
+      expect(res.status).toBe(200);
+      expect(res.headers.get('Content-Type')).toBe('text/plain; charset=utf-8');
+      expect(await res.text()).toBe('hey');
+    });
+  });
+
+  describe('.send(Buffer)', () => {
+    test('should keep charset in Content-Type', async () => {
+      mockListener.mockImplementation((req, res) => {
+        res.setHeader('Content-Type', 'text/plain; charset=iso-8859-1');
+        res.send(Buffer.from('hi'));
+      });
+
+      const res = await fetchWithProxyReq(url);
+      expect(res.status).toBe(200);
+      expect(res.headers.get('Content-Type')).toBe(
+        'text/plain; charset=iso-8859-1'
+      );
+      expect(await res.text()).toBe('hi');
+    });
+
+    test('should set Content-Length', async () => {
+      mockListener.mockImplementation((req, res) => {
+        res.send(Buffer.from('½ + ¼ = ¾'));
+      });
+
+      const res = await fetchWithProxyReq(url);
+      expect(res.status).toBe(200);
+      expect(Number(res.headers.get('content-length'))).toBe(12);
+      expect(await res.text()).toBe('½ + ¼ = ¾');
+    });
+
+    test('should send as octet-stream', async () => {
+      mockListener.mockImplementation((req, res) => {
+        res.send(Buffer.from('hello'));
+      });
+
+      const res = await fetchWithProxyReq(url);
+      expect(res.status).toBe(200);
+      expect(res.headers.get('Content-Type')).toBe('application/octet-stream');
+      expect((await res.buffer()).toString('hex')).toBe(
+        Buffer.from('hello').toString('hex')
+      );
+    });
+
+    test('should set ETag', async () => {
+      mockListener.mockImplementation((req, res) => {
+        res.send(Buffer.alloc(999, '-'));
+      });
+
+      const res = await fetchWithProxyReq(url);
+      expect(res.status).toBe(200);
+      expect(res.headers.get('ETag')).toBe(
+        'W/"3e7-qPnkJ3CVdVhFJQvUBfF10TmVA7g"'
+      );
+    });
+
+    test('should not override Content-Type', async () => {
+      mockListener.mockImplementation((req, res) => {
+        res.setHeader('Content-Type', 'text/plain; charset=utf-8');
+        res.send(Buffer.from('hey'));
+      });
+
+      const res = await fetchWithProxyReq(url);
+      expect(res.status).toBe(200);
+      expect(res.headers.get('Content-Type')).toBe('text/plain; charset=utf-8');
+      expect(await res.text()).toBe('hey');
+    });
+
+    test('should not override ETag', async () => {
+      mockListener.mockImplementation((req, res) => {
+        res.setHeader('ETag', '"foo"');
+        res.send(Buffer.from('hey'));
+      });
+
+      const res = await fetchWithProxyReq(url);
+      expect(res.status).toBe(200);
+      expect(res.headers.get('ETag')).toBe('"foo"');
+      expect(await res.text()).toBe('hey');
+    });
+  });
+
+  describe('.send(Object)', () => {
+    test('should send as application/json', async () => {
+      mockListener.mockImplementation((req, res) => {
+        res.send({ name: 'tobi' });
+      });
+
+      const res = await fetchWithProxyReq(url);
+      expect(res.status).toBe(200);
+      expect(res.headers.get('Content-Type')).toBe(
+        'application/json; charset=utf-8'
+      );
+      expect(await res.text()).toBe('{"name":"tobi"}');
+    });
+  });
+
+  describe('when the request method is HEAD', () => {
+    test('should ignore the body', async () => {
+      mockListener.mockImplementation((req, res) => {
+        res.send('yay');
+      });
+
+      // TODO: fix this test
+      // node-fetch is automatically ignoring the body so this test will never fail
+      const res = await fetchWithProxyReq(url, { method: 'HEAD' });
+      expect(res.status).toBe(200);
+      expect((await res.buffer()).toString()).toBe('');
+    });
+  });
+
+  describe('when .statusCode is 204', () => {
+    test('should strip Content-* fields, Transfer-Encoding field, and body', async () => {
+      mockListener.mockImplementation((req, res) => {
+        res.statusCode = 204;
+        res.setHeader('Transfer-Encoding', 'chunked');
+        res.send('foo');
+      });
+
+      const res = await fetchWithProxyReq(url);
+      expect(res.status).toBe(204);
+      expect(res.headers.get('Content-Type')).toBe(null);
+      expect(res.headers.get('Content-Length')).toBe(null);
+      expect(res.headers.get('Transfer-Encoding')).toBe(null);
+      expect(await res.text()).toBe('');
+    });
+  });
+
+  describe('when .statusCode is 304', () => {
+    test('should strip Content-* fields, Transfer-Encoding field, and body', async () => {
+      mockListener.mockImplementation((req, res) => {
+        res.statusCode = 304;
+        res.setHeader('Transfer-Encoding', 'chunked');
+        res.send('foo');
+      });
+
+      const res = await fetchWithProxyReq(url);
+      expect(res.status).toBe(304);
+      expect(res.headers.get('Content-Type')).toBe(null);
+      expect(res.headers.get('Content-Length')).toBe(null);
+      expect(res.headers.get('Transfer-Encoding')).toBe(null);
+      expect(await res.text()).toBe('');
+    });
+  });
+
+  // test('should always check regardless of length', async () => {
+  //   const etag = '"asdf"';
+
+  //   mockListener.mockImplementation((req, res) => {
+  //     res.setHeader('ETag', etag);
+  //     res.send('hey');
+  //   });
+
+  //   const res = await fetchWithProxyReq(url, {
+  //     headers: { 'If-None-Match': etag },
+  //   });
+  //   expect(res.status).toBe(304);
+  // });
+
+  // test('should respond with 304 Not Modified when fresh', async () => {
+  //   const etag = '"asdf"';
+
+  //   mockListener.mockImplementation((req, res) => {
+  //     res.setHeader('ETag', etag);
+  //     res.send(Array(1000).join('-'));
+  //   });
+
+  //   const res = await fetchWithProxyReq(url, {
+  //     headers: { 'If-None-Match': etag },
+  //   });
+  //   expect(res.status).toBe(304);
+  // });
+
+  // test('should not perform freshness check unless 2xx or 304', async () => {
+  //   const etag = '"asdf"';
+
+  //   mockListener.mockImplementation((req, res) => {
+  //     res.status(500);
+  //     res.setHeader('ETag', etag);
+  //     res.send('hey');
+  //   });
+
+  //   const res = await fetchWithProxyReq(url, {
+  //     headers: { 'If-None-Match': etag },
+  //   });
+  //   expect(res.status).toBe(500);
+  //   expect(await res.text()).toBe('hey');
+  // });
+
+  describe('etag', () => {
+    test('should send ETag', async () => {
+      mockListener.mockImplementation((req, res) => {
+        res.send('kajdslfkasdf');
+      });
+
+      const res = await fetchWithProxyReq(url);
+      expect(res.status).toBe(200);
+      expect(res.headers.get('ETag')).toBe('W/"c-IgR/L5SF7CJQff4wxKGF/vfPuZ0"');
+    });
+
+    test('should send ETag for empty string response', async () => {
+      mockListener.mockImplementation((req, res) => {
+        res.send('');
+      });
+
+      const res = await fetchWithProxyReq(url);
+      expect(res.status).toBe(200);
+      expect(res.headers.get('ETag')).toBe('W/"0-2jmj7l5rSw0yVb/vlWAYkK/YBwk"');
+    });
+
+    test('should send ETag for long response', async () => {
+      mockListener.mockImplementation((req, res) => {
+        res.send(Array(1000).join('-'));
+      });
+
+      const res = await fetchWithProxyReq(url);
+      expect(res.status).toBe(200);
+      expect(res.headers.get('ETag')).toBe(
+        'W/"3e7-qPnkJ3CVdVhFJQvUBfF10TmVA7g"'
+      );
+    });
+
+    test('should not override ETag when manually set', async () => {
+      mockListener.mockImplementation((req, res) => {
+        res.setHeader('etag', '"asdf"');
+        res.send('hello');
+      });
+
+      const res = await fetchWithProxyReq(url);
+      expect(res.status).toBe(200);
+      expect(res.headers.get('ETag')).toBe('"asdf"');
+    });
+
+    test('should not send ETag for res.send()', async () => {
+      mockListener.mockImplementation((req, res) => {
+        res.send();
+      });
+
+      const res = await fetchWithProxyReq(url);
+      expect(res.status).toBe(200);
+      expect(res.headers.get('ETag')).toBe(null);
+    });
+  });
+});
+
+// tests based on expressjs test suite
+// see https://github.com/expressjs/express/blob/master/test/res.json.js
+describe('res.json', () => {
+  test('should send be chainable', async () => {
+    const spy = jest.fn();
+
+    mockListener.mockImplementation((req, res) => {
+      spy(res, res.json({ hello: 'world' }));
+    });
+
+    await fetchWithProxyReq(url);
+
+    const [a, b] = spy.mock.calls[0];
+    expect(a).toBe(b);
+  });
+
+  test('res.json() should send an empty body', async () => {
+    mockListener.mockImplementation((req, res) => {
+      res.json();
+    });
+
+    await fetchWithProxyReq(url);
+
+    const res = await fetchWithProxyReq(url);
+    expect(res.status).toBe(200);
+    expect(res.headers.get('content-type')).toBe(
+      'application/json; charset=utf-8'
+    );
+    expect(await res.text()).toBe('');
+  });
+
+  describe('.json(object)', () => {
+    test('should not override previous Content-Types', async () => {
+      mockListener.mockImplementation((req, res) => {
+        res.setHeader('content-type', 'application/vnd.example+json');
+        res.json({ hello: 'world' });
+      });
+
+      const res = await fetchWithProxyReq(url);
+      expect(res.status).toBe(200);
+      expect(res.headers.get('content-type')).toBe(
+        'application/vnd.example+json; charset=utf-8'
+      );
+      expect(await res.text()).toBe('{"hello":"world"}');
+    });
+
+    test('should set Content-Length and Content-Type', async () => {
+      mockListener.mockImplementation((req, res) => {
+        res.json({ hello: '½ + ¼ = ¾' });
+      });
+
+      const res = await fetchWithProxyReq(url);
+      expect(res.status).toBe(200);
+      expect(res.headers.get('content-type')).toBe(
+        'application/json; charset=utf-8'
+      );
+      expect(Number(res.headers.get('content-length'))).toBe(24);
+      expect(await res.text()).toBe('{"hello":"½ + ¼ = ¾"}');
+    });
+
+    describe('when given primitives', () => {
+      test('should respond with json for null', async () => {
+        mockListener.mockImplementation((req, res) => {
+          res.json(null);
+        });
+
+        const res = await fetchWithProxyReq(url);
+        expect(res.status).toBe(200);
+        expect(res.headers.get('content-type')).toBe(
+          'application/json; charset=utf-8'
+        );
+        expect(await res.text()).toBe('null');
+      });
+
+      test('should respond with json for Number', async () => {
+        mockListener.mockImplementation((req, res) => {
+          res.json(300);
+        });
+
+        const res = await fetchWithProxyReq(url);
+        expect(res.status).toBe(200);
+        expect(res.headers.get('content-type')).toBe(
+          'application/json; charset=utf-8'
+        );
+        expect(await res.text()).toBe('300');
+      });
+
+      test('should respond with json for String', async () => {
+        mockListener.mockImplementation((req, res) => {
+          res.json('str');
+        });
+
+        const res = await fetchWithProxyReq(url);
+        expect(res.status).toBe(200);
+        expect(res.headers.get('content-type')).toBe(
+          'application/json; charset=utf-8'
+        );
+        expect(await res.text()).toBe('"str"');
+      });
+    });
+
+    test('should respond with json when given an array', async () => {
+      mockListener.mockImplementation((req, res) => {
+        res.json(['foo', 'bar', 'baz']);
+      });
+
+      const res = await fetchWithProxyReq(url);
+      expect(res.status).toBe(200);
+      expect(res.headers.get('content-type')).toBe(
+        'application/json; charset=utf-8'
+      );
+      expect(await res.text()).toBe('["foo","bar","baz"]');
+    });
+
+    test('should respond with json when given an object', async () => {
+      mockListener.mockImplementation((req, res) => {
+        res.json({ name: 'tobi' });
+      });
+
+      const res = await fetchWithProxyReq(url);
+      expect(res.status).toBe(200);
+      expect(res.headers.get('content-type')).toBe(
+        'application/json; charset=utf-8'
+      );
+      expect(await res.text()).toBe('{"name":"tobi"}');
+    });
+  });
+});

packages/node-bridge/types.ts

@@ -1,5 +1,11 @@
 /// <reference types="node" />
-import { Server, IncomingHttpHeaders, OutgoingHttpHeaders } from 'http';
+import {
+  Server,
+  IncomingHttpHeaders,
+  OutgoingHttpHeaders,
+  ServerResponse,
+  IncomingMessage,
+} from 'http';
 export interface VercelProxyEvent {
   Action: string;
   body: string;
@@ -37,3 +43,20 @@ export type LauncherConfiguration = {
   awsLambdaHandler?: string;
   useRequire?: boolean;
 };
+
+export type VercelRequestCookies = { [key: string]: string };
+export type VercelRequestQuery = { [key: string]: string | string[] };
+export type VercelRequestBody = any;
+
+export type VercelRequest = IncomingMessage & {
+  query: VercelRequestQuery;
+  cookies: VercelRequestCookies;
+  body: VercelRequestBody;
+};
+
+export type VercelResponse = ServerResponse & {
+  send: (body: any) => VercelResponse;
+  json: (jsonBody: any) => VercelResponse;
+  status: (statusCode: number) => VercelResponse;
+  redirect: (statusOrUrl: string | number, url?: string) => VercelResponse;
+};