Type value does not exist on MultipartFile when using onFile

[mhamid3d]

Prerequisites

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

Fastify version

5.2.1

Plugin version

9.0.3

Node.js version

23.7.0

Operating system

Windows

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

11

Description

When using onFile, the part does not have typings for value

So this code from the readme is not valid. As such I am providing this github repo as the reproducible example:

async function onFile(part) {
  const buff = await part.toBuffer()
  const decoded = Buffer.from(buff.toString(), 'base64').toString()
  part.value = decoded // set `part.value` to specify the request body value
}

fastify.register(require('@fastify/multipart'), { attachFieldsToBody: 'keyValues', onFile })

fastify.post('/upload/files', async function (req, reply) {
  const uploadValue = req.body.upload // access file as base64 string
  const fooValue = req.body.foo       // other fields
})

Link to code that reproduces the bug

https://github.com/fastify/fastify-multipart

Expected Behavior

Typings for value on MultipartFile

[mcollina]

Thanks for reporting!

Can you provide steps to reproduce? We often need a reproducible example, e.g. some code that allows someone else to recreate your problem by just copying and pasting it. If it involves more than a couple of different file, create a new repository on GitHub and add a link to that.

[mhamid3d]

If using Typescript, this should produce an error on part.value

fasitfy.register(import('@fastify/multipart'), {
        attachFieldsToBody: 'keyValues',
        onFile: async (part) => {
            const buff = await part.toBuffer();
            part.value = buff.toString('base64');
        },
    });