Break multi bytes UTF-8 characters when parsing in Node-style

[jdesboeufs]

PapaParse breaks multi bytes UTF-8 characters when they are sliced between different chunks of Buffer.
For example ç would become ��.

To reproduce:

const Papa = require('papaparse')
const {PassThrough} = require('stream')

const csvFileString = 'first_name,last_name\nFrançois,Mitterrand\n'

const input = new PassThrough()
const parser = Papa.parse(Papa.NODE_STREAM_INPUT, {header: true})

input.pipe(parser)

parser.on('data', row => console.log(row))

input.write(Buffer.from(csvFileString).slice(0, 26))
input.write(Buffer.from(csvFileString).slice(26))
input.end()

{ first_name: 'Fran��ois', last_name: 'Mitterrand' }

A workaround is to ensure UTF-8 decoding with string_decoder (internal Node module), WHATWG TextDecoder or with iconv-lite (user-land dependency).
But a better answer is to use string_decoder or TextDecoder into PapaParse, in place of chunk.toString().

Related to #751

[jdesboeufs]

Option 1: using string_decoder in PapaParse

Pros: straightforward bugfix
Cons: will depend on a polyfill when using Node stream syntax in browser. Possibly a breaking change

Option 2 using WHATWG TextDecoder in PapaParse

Pros: future-proof and universal bugfix
Cons: require Node.js 8.3+, Firefox 19/20, Chrome 38+

Option 3: deprecate or forbid using PapaParse with a stream of Buffer

Throw an error when using with a stream of Buffer => force user to decode stream on its own (add example with iconv-lite)

Pros: keep PapaParse simple
Cons: breaking change if no deprecation

[Narretz]

I'm trying to proactively use the iconv-lite option. Can you check if this pseudo implementation correct? Could also be added to the docs after clean-up.
It does work but I haven't tested all edge cases.
I assume iconv-lite guarantees that multi bytes UTF-8 characters are kept together?

And is there a way to get the "meta" field in the streaming api? on('data') only gets you the data part of the result.
See

PapaParse/papaparse.js

Lines 917 to 918 in 1f2c733

	var data = results.data;
	if (!stream.push(data) && !this._handle.paused()) {

I assume that's intentional?

    import { parse, NODE_STREAM_INPUT } from 'papaparse';
    import { decodeStream } from 'iconv-lite';
    import { pipeline } from 'stream';

    const stream // some ReadStream

    const converterStream = decodeStream('utf8');

    const csvStream = parse(NODE_STREAM_INPUT, {
      header: true,
    });

    csvStream.on('data', (data) => {
      console.log('do something with the data')
      // can I get the meta info here?
    });

    csvStream.on('end', (result) => {});

    pipeline(stream, converterStream, csvStream, (err) => {
      console.log('stream complete', err);
    });

[Kaiido]

If I may, I believe the WHATWG's TextDecoder option would be your best move here.
As already said it is future-proof, and can be polyfilled if needed.
It would also fix a bug in browsers with the chunk option: https://jsfiddle.net/3zypkqtg/ (not sure if yet another report is needed for that).

[kaligrafy]

any news on this? I tried every method to fix it, but it doesn't work or it just take forever to read the stream. What should be done in the mentime to be able to read mutil-byte UTF-8 cjaracters when streaming to papa?

[fatso83]

@kaligrafy I would just look at the commit history in https://github.com/beamworks/react-csv-importer to see how they worked around it using TextEncoder.