Set encoding of the request to utf8 before listening on data events

[lbdremy]

Hello,

I'm running into a case where the data event handler is called before the set encoding is called, in this case I end up having chunks as an empty string and data is a Buffer thus raising the error `Possibly unhandled TypeError: Object has no method 'copy'
I always thought the data event handler was called after the next tick, but it does not seem to be the case, or I am missing something.
Moving the setEncoding method before attaching the handler resolves my issue.

Thank

[nkzawa]

Hmm, it looks this PR doesn't change the behavior to me. Anyway, I'd like to reproduce the problem. How can I do that?

[STRML]

We are seeing this in #356 and primus/primus#196 (comment). It is very hard to reproduce and I have not successfully been able to do so, but I am seeing it hit our production servers about once or twice a week. Last time I saw it, I was running iojs v2.5.0.

I am, however, able to reproduce the issue using the following script:

var stream = require('stream');

var a = new stream.PassThrough();

a.write('foobar');

console.log('before handler');
a.on('data', function(chunk) {
  console.log('data handler', chunk);
});
console.log('after handler');

a.setEncoding('utf8');

The correct output is:

before handler
after handler
data handler foobar

Every Node version > 0.10 has the correct behavior that I tested, but 0.10.40 does not:

before handler
data handler <Buffer 66 6f 6f 62 61 72>
after handler

Since engine.io still supports 0.10 it makes sense to merge this. I am not sure why I was seeing it in other versions - I will continue to investigate - but this is still a solid fix and needed for 0.10 users.

[STRML]

For future reference, this appears to be the commit that fixed the bug, which landed in v0.11.5. It's also known as streams3. It makes the commit comment "There is no API change beyond this added flexibility" somewhat inaccurate: nodejs/node@0f8de5e#diff-ba6a0df0f5212f5cba5ca5179e209a17R709

[lpinca]

@STRML good job!

[STRML]

@nkzawa Could you please review?

[nkzawa]

@STRML 👍

[rauchg]

Awesome! Thank you :)

[STRML]

Thanks @rauchg, had this biting us at random for a long time now.

[rauchg]

Yep, I'll get this published asap