Reply with a long string will encounter "Premature close #215"

[stanleyxu2005]

Prerequisites

• I have written a descriptive issue title
• I have searched existing issues to ensure the bug has not already been reported

Fastify version

4.26.2

Plugin version

7.0.1

Node.js version

18.17.1

Operating system

Windows

Operating system version (i.e. 20.04, 11.3, 10)

Windows 11

Description

Similar issue to #215

I'm sending a long string as response, with fastify-compress enabled, it will fail with error Premature close.

Steps to Reproduce

  const fastify = new Fastify({})

  fastify.register(fastifyCompress) // #1 disable this line will work

  fastify.get('/subscription', async (req, reply) => {

    const longString = new Array(1024).fill('a').join('') // <--- build a string, whose length is >= 1024 (compress.threshold)

    // return reply.send(longString) // <--- ok, string will be sent

    reply.send(longString) // <--- not ok, if `return ` is forgotten to be added at block end
  })

Expected Behavior

Regardless return is added or not, it should always respond with expected content.

Question

Do you think, there is something can be improved in @fastify/compress

[gurgunday]

If you have an async handler, you should always return the body instead of using reply.send:

  const fastify = new Fastify({})

  fastify.register(fastifyCompress) // #1 disable this line will work

  fastify.get('/subscription', async (req, reply) => {

    const longString = new Array(1024).fill('a').join('') // <--- build a string, whose length is >= 1024 (compress.threshold)

    return longString
  })

Or:

  const fastify = new Fastify({})

  fastify.register(fastifyCompress) // #1 disable this line will work

  fastify.get('/subscription', (req, reply) => {

    const longString = new Array(1024).fill('a').join('') // <--- build a string, whose length is >= 1024 (compress.threshold)

    reply.send(longString)
  })

You can find more information here: https://fastify.dev/docs/latest/Reference/Routes/#promise-resolution

[stanleyxu2005]

@gurgunday Thanks for sharing info.

It's a bit tricky for a new user. I'd now strictly call return reply.send(...). Syntax sugar is painful when migrating between different frameworks.

I was not aware this when migrating from Koa of promise based routes.

// in koa
async someGetRoute(ctx) {
  ctx.body = await getMyDataAsync()
}

// in fastify
async someGetRoute(request, reply) {
  return reply.send(await getMyDataAsync())
}