Use Babili for minification

[guybedford]

We can add a step to the compiler at https://github.com/systemjs/builder/blob/master/compilers/compiler.js, that returns source, sourceMap, minifiedSource, minifiedSourceMap by running another compile phase on the same AST after the initial unminified compile. We can then cache all four along with the load record and solve the problem of having granular caching of minification as well (#209).

If anyone is interested in working on this contributions would be really really amazing.

[timfish]

I had a quick look at what would happen if I replace minify() in output.js with some rather hacky code calling the latest uglify-es:

function minify(output, fileName, mangle, uglifyOpts) {
  var uglify = require('uglify-es');

  let files = {};
  files[fileName] = output.source;

  var result = uglify.minify(files, {
    sourceMap: {
      content: output.sourceMap,
      url: fileName + ".map"
    }
  });

  output.source = result.code;
  output.sourceMap = result.map;

  return output;
}

All the tests pass apart from these two:

  106 passing (16s)
  1 pending
  2 failing

  1) Test tree builds - Babel SFX tree build:
     Error: Phantom test failed test/test-sfx.html failed.
      at Error (native)
      at ChildProcess.<anonymous> (C:\Users\tim\Documents\Repos\systemjs-builder\test\test-build.js:28:16)
      at maybeClose (internal/child_process.js:877:16)
      at Process.ChildProcess._handle.onexit (internal/child_process.js:226:5)

  2) Test tree builds - TypeScript SFX tree build:
     Error: Phantom test failed test/test-sfx.html failed.
      at Error (native)
      at ChildProcess.<anonymous> (C:\Users\tim\Documents\Repos\systemjs-builder\test\test-build.js:28:16)
      at maybeClose (internal/child_process.js:877:16)
      at Process.ChildProcess._handle.onexit (internal/child_process.js:226:5)

I tried these changes on v0.15.x as that's the version which aurelia-bundler is still targeting but I couldn't actually get the bundle to load in my app. The new bundle is calling System.registry.get in places where previously it called System.get and falls over quickly. I'm guessing I haven't worked out which SystemJS version goes with which bundler version. For various reasons I'm still stuck on systemjs@0.19.

[guybedford]

@timfish amazing, thanks for giving this a go! It's been sitting here way to long just waiting to be picked up by someone...

Yes the builder version 0.15 branch is for SystemJS 0.19. The code is exactly the same though, so if you wanted to try an initial PR against the 0.15 branch here, we can then merge it into the 0.16 branch as well when it's ready.

For the build failures, it may be due to the fact that certain globals must not be altered for builds. A careful comparison of the output should help track that down here. I'd be happy to give that a go too, if there was a PR to work with as a reference.

Not that carefully checking the source maps with multiple files is an important part of polishing this work for release, but having something to work with as a start would be great.

[timfish]

One thing I did notice was that aurelia-bundler is failing to bundle async code even with minify: false so I've got to have a look there too. I assumed with minify disabled, the code wouldn't even go through uglify.

Ideally we'd keep uglifyOpts the same so it wouldn't be a breaking change. However, in v2 uglifyOpts is used only for compression options and in uglify@harmony, compression options are only part of the config.

I'm guessing if you'd want this on both 0.15 and 0.16 we'll keep the same configuration options for now?

[guybedford]

@timfish the builder project on the 0.15 branch still runs code through Traceur. This is removed in the 0.16 branch though I believe so minify should be the only dependency there. Let me know if there is anything I can do to help with the 0.20 SystemJS upgrade here as well if that is a goal.

Yes uglifyOpts is a little inconsistent right now, there's also #689 here. Ideally, backwards compatibillity with a cleaner modern interface and to deprecate the old would be the best, but otherwise a breaking change could be possible if that isn't an option.