Allow using a custom analyzer

[singpolyma-shopify]

Export ExportsWalker to allow building custom walkers for analysis tools.

Allow an option to asc.main to get called with the Program object to
facilitate building custom CLIs on top of asc that call their own analysis
logic.

[dcodeIO]

This seems like it could reuse the existing afterCompile transform, so exposing the walker would be sufficient.

[singpolyma-shopify]

@dcodeIO that transform looks like it gives access to a Module but I'm not sure I can get the Program from there in order to run a walker? Maybe I'm just missing it.

[MaxGraey]

If you need program better use afterParse hook:

afterParse(parser: Parser): void {
  const program = parser.program;
  ...
}

or you could save program reference and use it inside afterCompile hook later

[singpolyma-shopify]

@MaxGraey thanks, I have it working using that strategy (save program reference from afterParse, then use in afterCompile).

So just the export, then.

[dcodeIO]

Alright, thanks! Maybe a word of caution: ExportsWalker is responsible for generating definitions, which hasn't been tested a lot. Might or might not work as expected, so if there are any issues, let us know :)