Allow local modules to work as UIs and Reporters

[giggio]

(This was PR #1240, we are starting over)
The current way dependencies are handled forces us to have a ui interface (or reporter) installed globally.
I am trying to write another ui interface and unless I use an absolute path or install the module globally I can't load the ui interface. The ideal scenario is to do this per application, so when someone clones the repo the tests just work. The current way will force the developer to globally install mocha and also globally install the module I am writing with the custom ui interface.
This happens because when you require a name, the lookup starts from the executable file location, mocha (global node_modules dir). It doesn't do the lookup from the node_modules folder where the mocha command is ran (pwd).

https://github.com/visionmedia/mocha/blob/755f05410d8bdb1218073b74755089998b98a0ca/lib/mocha.js#L153

Currently mocha adds the cwd to modules.path on _mocha like so:

https://github.com/visionmedia/mocha/blob/755f05410d8bdb1218073b74755089998b98a0ca/bin/_mocha#L152

module.paths.push(cwd, join(cwd, 'node_modules'));

But not on mocha.js.

This will only work for immediate requires, only when they are required directly from _mocha. When mocha.js tries to load the new ui interface later it can't find it, because its module.paths is different from _mocha's module.paths.
To be able to load from a local node_modules folder it would be needed to set module.paths from where the require for the ui is set, at mocha.js.
This PR does just that.

[jbnicolai]

The current way will force the developer to globally install mocha and also globally install the module I am writing with the custom ui interface.

So this is what confused me originally. There is no need to install mocha globally, but if running mocha globally then it will only find globally installed UIs and reporters as well. However, when running locally, locally installed reporters and UIs work just find.

What this PR adds is that a globally running mocha will source locally installed or linked reporters and UIs.

@giggio does that about sum it up? ;-)

[giggio]

@jbnicolai Yes!

[jbnicolai]

Am I correct in understanding that this fixes UIs, but not reporters? I'm just checking against the earlier installed mocha-teamcity-reporter, and still seeing the same error.

[jbnicolai]

[giggio]

It fixes both. I just tested:

~/proj/rabiscos/mochatestreporter$ mocha --ui mocha-retry                                                                                                                                              

/home/giovanni/.nvm/v0.10.26/lib/node_modules/mocha/lib/mocha.js:154
  if (!this._ui) throw new Error('invalid interface "' + name + '"');
                       ^
Error: invalid interface "mocha-retry"
    at Mocha.ui (/home/giovanni/.nvm/v0.10.26/lib/node_modules/mocha/lib/mocha.js:154:24)
    at Object.<anonymous> (/home/giovanni/.nvm/v0.10.26/lib/node_modules/mocha/bin/_mocha:195:7)
    at Module._compile (module.js:456:26)
    at Object.Module._extensions..js (module.js:474:10)
    at Module.load (module.js:356:32)
    at Function.Module._load (module.js:312:12)
    at Function.Module.runMain (module.js:497:10)
    at startup (node.js:119:16)
    at node.js:902:3
~/proj/rabiscos/mochatestreporter$ ../../mocha/bin/mocha --ui mocha-retry                                                                                                                              


  a suite
    ✓ tests 


  1 passing (7ms)

~/proj/rabiscos/mochatestreporter$ mocha -R mocha-teamcity-reporter                                                                                                                                    

/home/giovanni/.nvm/v0.10.26/lib/node_modules/mocha/lib/mocha.js:137
    if (!_reporter) throw new Error('invalid reporter "' + reporter + '"');
                          ^
Error: invalid reporter "mocha-teamcity-reporter"
    at Mocha.reporter (/home/giovanni/.nvm/v0.10.26/lib/node_modules/mocha/lib/mocha.js:137:27)
    at Object.<anonymous> (/home/giovanni/.nvm/v0.10.26/lib/node_modules/mocha/bin/_mocha:191:7)
    at Module._compile (module.js:456:26)
    at Object.Module._extensions..js (module.js:474:10)
    at Module.load (module.js:356:32)
    at Function.Module._load (module.js:312:12)
    at Function.Module.runMain (module.js:497:10)
    at startup (node.js:119:16)
    at node.js:902:3
~/proj/rabiscos/mochatestreporter$ ../../mocha/bin/mocha -R mocha-teamcity-reporter
##teamcity[testSuiteStarted name='a suite']
##teamcity[testStarted name='tests' captureStandardOutput='true']
##teamcity[testFinished name='tests' duration='0']
##teamcity[testSuiteFinished name='a suite' duration='NaN']
##teamcity[testSuiteFinished name='mocha.suite' duration='5']
~/proj/rabiscos/mochatestreporter$ 

[giggio]

When you run mocha you will always get the error, because you are running the global one, not yet fixed.
To test it you either globally install the version with the fix, or run it from a separate directory (like I did above).

[jbnicolai]

... ok, that last mistake on my part was just embarrassing.

Tested, and works perfectly well indeed 😄
Again, thanks for all the work you put into this!

[giggio]

Nice! Thanks for the support. I will be able to run regular mocha again. :D
I am able to help on other issues, just let me know if you need some help elsewhere.

[jbnicolai]

Nope, already happy you merged in the CDN option on chromedriver a while back ;-) fixed some issues I was having being my proxy at work.