add test demonstrating #595 in firefox

[devoidfury]

this fails for me about half the time in browser: Firefox 58.0.2 (64-bit)

The kind of change this PR does introduce

• a bug fix
• a new feature
• an update to the documentation
• a code change that improves performance
• other
  Test

Current behaviour

connection :: should work in a worker

Error: expected 'пойдÑ\u0083 Ñ\u0081аÑ\u0082Ñ\u008c вÑ\u0081ем Ð' to equal 'пойду сать всем мпокойной ночи' (http://localhost:8080/__zuul/test-bundle.js:413)

    at process.on/global.onerror (__zuul/framework.js:6458:10)

Other information (e.g. related issues)

Issue #595

[darrachequesne]

Thanks, I could indeed reproduce the issue.

I think this is linked to #592 (and socketio/engine.io-parser#81, eventually).

Due to a bug in the XHR implementation of the Firefox Worker, the line here throws:

if (xhr.readyState === 2) {
  try {
    var contentType = xhr.getResponseHeader('Content-Type');
    if (contentType !== 'application/octet-stream') {
      xhr.responseType = 'text';
    }
  } catch (e) {}
}

So the content is decoded as a buffer, which breaks UTF-8 encoding.

[devoidfury]

I added a test for binary data in a worker, as well as adding a fix. Now instead of eagerly switching the responeType to 'arrayBuffer', delay doing that until checking the response headers. This seems to fix the issue and still works with binary data.

[darrachequesne]

Thanks!