Improve developer experience

🚀 Feature Proposal

Today, I needed to develop a simple image upload service in fastify and it felt unsatisfying.

Motivation

Handling multipart form data should be dead simple and intuitive in fastify.

• Support async / await (async stream iterators)
• Zero boilerplate, provide fastify-hooks to do all this stuff with good defaults (like in expressjs/multer upload.single("uploaded_file") )
• Delegate busboy failures to fastify (like in expressjs https://github.com/expressjs/multer/blob/6b5fff5feaf740f249b1b2858e5d06009cbd245c/lib/make-middleware.js#L167-L170)

Example

In https://eggjs.org/en/basics/controller.html#acquiring-the-submitted-files you can easily switch different modes without dealing with too much boilerplate.

// Single file in disk storage mode
app.post("/images", async (req, res) => {
  req.file.filename
  req.file.mimetype
  // async / await
})

// Multiple files in disk storage mode
app.post("/images", async (req, res) => {
  req.files
})

// Single file in stream mode
app.post("/images", async (req, res) => {
   const stream = await ctx.getFileStream();
})

// Multiple files in stream mode
app.post("/images", async (req, res) => {
 const parts = ctx.multipart();
    let part;
    // parts() return a promise
    while ((part = await parts()) != null) {}
})

in fastify you need for the same behaviour a lot of boilerplate and you are responsible to handle all cases manually.

fastify.register(require('fastify-multipart'))

fastify.post('/upload', function (req, reply) {
  const mp = req.multipart(handler, function (err) {
    console.log('###2');
    if (err) {
      reply.send(err)
      return
    }
    console.log('upload completed', process.memoryUsage().rss)
    reply.code(200).send()
  })

  mp.on('field', function (key, value) {
    console.log('form-data', key, value)
  })

  function handler (field, file, filename, encoding, mimetype) {
    pump(file, fs.createWriteStream('a-destination'), (err) => {
      console.log('###1');
    })
  }
})

Logs:

server listening on 3000
###2
upload completed 31477760
###1

Additional problems for the users:

• onEnd is fired before the file was written.

[StarpTech]

Since this is the core package we should try to improve this package or switch to fastify-multer entirely.

[fox1t]

We might also move fastify-multer under fastify organization here on GitHub.