Enable parallelBabel

[gitKrystan]

Supersedes #11

[ef4]

These log lines:

Babel: ember-this-fallback (3) | 1175ms (391 ms)

are telling you how long it took to transpile the ember-this-fallback addon's own runtime javascript code. Probably that is not very relevant, you really want to know how long it takes the addon to transpile the app's code, because there's generally a lot more app code.

(Also I don't necessarily believe these self-reported numbers are apples-to-apples with parallelism turning on and off. I'd look at the impact on the total build.)

I would guess that you really only want to run the ast transform on the app's code, not on the addon's own code, in which case you can say so explicitly:

setupPreprocessorRegistry: function (type, registry) {
+ if (type === 'parent') {  
  registry.add('htmlbars-ast-plugin', this._buildPlugin());
+ }
},

Are we talking about performance differences under a classic build or under embroider? Under embroider, the above difference might have a measurable impact because it's changing your addon from one that needs custom transforms to one that does not, which skips an entire babel pass of the addon's code.