Can this work with `this.emitError` (Loader API) ?

[ajbrun]

I was hoping to make a pull request for this, but I've run into difficulties, so I wondering if anyone else has any thoughts/suggestions. My idea was to allow this loader to work with the emitError function that webpack provides in its loaders. This could either be done by default or via a parameter, but I've not managed to get the basic functionality working yet.

I was aiming towards something like what eslint loader does:
https://github.com/MoOx/eslint-loader/blob/master/index.js#L102

Which with the webpack hot middleware will output a response to the browser similar to what's shown here:
webpack-contrib/webpack-hot-middleware#9 (comment)

So far I have this, but it doesn't emit the error as expected for a failing test. It shows the error in the console, just not on screen or in the browser's console as it usually does with an emitError.

var Mocha = require('mocha');
var babel = require('babel-core/register');

module.exports = function(content, map) {
  var webpack = this;

  var mocha = new Mocha({
    compilers: {
      js: babel
    }
  });
  mocha.ui('bdd');
  mocha.addFile(this.resourcePath);
  mocha.run().on("fail", function(test, err) {
    webpack.emitError(err);
  });

  return "console.log('Mocha loader run at '+new Date().toLocaleString());";
};

I have however found that if I remove all mocha code, and just emitError on condition of matching a string in the content, that works (albeit not on initial load), so the issue is the mocha code, which I haven't had much experience with.

if (content.indexOf('make error') >= 0) { //Works as expected webpack.emitError('error test'); }