8to9guide.md

title	permalink
restify 8.x to 9.x migration guide	/docs/8to9/

Introduction

restify 9.x comes with async/await support!

Breaking Changes

Drops support for Node.js 8.x

Restify requires Node.js version >=10.0.0.

Async/await support

async/await basic support for .pre(), .use() and route handlers.

Example

const restify = require('restify');

const server = restify.createServer({});

server.use(async (req, res) => {
  req.something = await doSomethingAsync();
});

server.get('/params', async (req, res) => {
  const value = await asyncOperation(req.something);
   res.send(value);
});

Middleware API (.pre() and .use())

server.use(async (req, res) => {
  req.something = await doSomethingAsync();
});

• fn.length === 2 (arity 2);
• fn instanceof AsyncFunction;
• if the async function resolves, it calls next();
• any value returned by the async function will be discarded;
• if it rejects with an Error instance it calls next(err);
• if it rejects with anything else it wraps in a AsyncError and calls next(err);

Route handler API

server.get('/something', async (req, res) => {
  const someData = await fetchSomeDataAsync();
  res.send({ data: someData });
});

• fn.length === 2 (arity 2);
• fn instanceof AsyncFunction;
• if the async function resolves without a value, it calls next();
• if the async function resolves with a string value, it calls next(string) (re-routes*);
• if the async function resolves with a value other than string, it calls next(any);
• if it rejects with an Error instance it calls next(err);
• if it rejects with anything else it wraps in a AsyncError and calls next(err) (error-handing**);

(*) Note about re-routing:

The 8.x API allows re-routing when calling next() with a string value. If the string matches a valid route, it will re-route to the given handler. The same is valid for resolving a async function. If the value returned by the async function is a string, it will try to re-route to the given handler.

(**) Note about error handling:

Although it is recommended to always reject with an instance of Error, in a async function it is possible to throw or reject without returning an Error instance or even anything at all. In such cases, the value rejected will be wrapped on a AsyncError.

Handler arity check

Handlers expecting 2 or fewer parameters added to a .pre(), .use() or route chain must be async functions, as:

server.use(async (req, res) => {
  req.something = await doSomethingAsync();
});

Handlers expecting more than 2 parameters shouldn't be async functions, as:

// This middleware will be rejected and restify will throw
server.use(async (req, res, next) => {
  doSomethingAsync(function callback(val) {
    req.something = val;
    next();
  });
});