Support the contentType of multipart field.

[msojocs]

Support plan

• which support plan is this issue covered by? (e.g. Community, Sponsor, or Enterprise):Community
• is this issue currently blocking your project? (yes/no):yes
• is this issue affecting a production system? (yes/no):no

Context

• node version:
• module (formidable) version: v18.18.2
• environment (e.g. node, browser, native, OS): node
• used with (i.e. popular names of modules): express
• any other relevant information:

What problem are you trying to solve?

const form = formidable({
        uploadDir: storagePath,
        createDirsFromUploads: true,
        keepExtensions: true,
    });
    form.parse<'chatType' | 'peerUid' | 'guildId', "file">(req, (err, fields, files) => {
        if (err) {
            log.error('file parse error:', err)
            next(err);
            return;
        }

            log.info('fields:', fields);
            log.info('files:', files);
    })

If the 'Content-Type' was set, formidable wil parse the field as file.

raw data:

POST http://127.0.0.1:8081/group/uploadFile HTTP/1.1
User-Agent: Apifox/1.0.0 (https://apifox.com)
Accept: */*
Host: 127.0.0.1:8081
Accept-Encoding: gzip, deflate, br
Connection: keep-alive
Content-Type: multipart/form-data; boundary=--------------------------420820768465130987175823
Content-Length: 279

----------------------------420820768465130987175823
Content-Disposition: form-data; name="chatType"

2
----------------------------420820768465130987175823
Content-Disposition: form-data; name="peerUid"
Content-Type: text/plain; charset=UTF-8

933286835
----------------------------420820768465130987175823--

result:

[2024-04-03 16:55:10.629] [info] [UploadFile] fields: { chatType: [ '2' ] }
[2024-04-03 16:55:10.629] [info] [UploadFile] files: {
  peerUid: [
    PersistentFile {
      _events: [Object: null prototype],
      _eventsCount: 1,
      _maxListeners: undefined,
      lastModifiedDate: 2024-04-03T08:55:10.629Z,
      filepath: 'D:\\GitHub\\Yukihana\\tmp\\storage\\7a8a74440325b47b92e55aa03',
      newFilename: '7a8a74440325b47b92e55aa03',
      originalFilename: null,
      mimetype: 'text/plain; charset=UTF-8',
      hashAlgorithm: false,
      size: 9,
      _writeStream: [WriteStream],
      hash: null,
      [Symbol(kCapture)]: false
    }
  ]
}

As you can see, when I set the contentType of field named peerUid(text/plain), it will be parsed as file.

Maybe we can just supprt the contentType text and file.

Do you have a new or modified API suggestion to solve the problem?

[msojocs]

https://github.com/node-formidable/formidable/issues/875

[msojocs]

const form = formidable({
        uploadDir: storagePath,
        createDirsFromUploads: true,
        keepExtensions: true,
    });
    form.onPart =  function (part) {
        log.info('part:', part)
        if (part.mimetype && !(part as any).headers['content-disposition']?.match(/filename="/)) {
            // we want it to be a "field" (cf https://github.com/node-formidable/formidable/issues/875 )
            part.mimetype = null
        }
        form._handlePart(part);
    }