How to Add/Modify CoffeeScript AST and write the result to a CoffeeScript file

[Milton Inostroza Aguilera]

Hey folks,

I would like to perform some changes in all the CoffeeScript files that are defined in a couple of repos that I have. I saw that by using coffeescript I can get a hold of the AST by doing the following

coffeescript = require 'coffee-script'
ast = coffee.nodes("my-file.coffee")

The problem with this approach is that there is no way to write the modified AST back to a coffee file. I got a suggestion of compiling the AST(coffeescript) to javascript, and then use js2coffee to write the result back to a coffeescript file. Is there a way to pass the modified AST(coffeescript) to js2coffee to generate a coffeescript file?

[Geoffrey Booth]

You basically want to fork the compile function from coffeescript.coffee. In particular, this line:

fragments = parser.parse(tokens).compileToFragments options

can be rewritten as:

nodes = parser.parse tokens
fragments = nodes.compileToFragments options

In between these two lines, you can manipulate the nodes however you want.

EDIT: Just noticed you’re trying to get to CoffeeScript in the end. Sorry, not sure how to get there. The above will at least let you make your own version of the CoffeeScript compiler that includes your AST manipulations, then as you said you could pass that generated JS through js2coffee.

[Milton Inostroza Aguilera]

@GeoffreyBooth thanks for the insight!

[Geoffrey Booth]

@minostro Did you ever figure this out?

[Milton Inostroza Aguilera]

@GeoffreyBooth nope...unfortunately, got pull into something else :(