SourceMap support to make debugging less annoying

[technicalpickles]

One of the most annoying things about debugging hubot .coffee scripts is the mismatch between the coffee source and the error stack traces. I came across this article talking about Mozilla adding better coffeescript via source maps, which sounds just like the thing I'm looking for

Some other things found along the way:

• http://www.html5rocks.com/en/tutorials/developertools/sourcemaps/
• http://badassjs.com/post/42588937391/node-js-source-map-support-for-better-compiled
• Support SourceMap nodejs/node-v0.x-archive#3712
• https://github.com/evanw/node-source-map-support

I think the node-source-map-support is probably the way to go, but I haven't been able to test thoroughly yet.

[atmos]

[technicalpickles]

Haven't had much luck with it. Sounds like a pretty recent development:

• http://www.coffeescriptlove.com/2013/03/coffeescript-16-source-maps.html
• a random person on serverfault it should just work with coffeescript-1.6.2

[technicalpickles]

From the original pull request to coffee-script that added support for source maps:

Line numbers in exceptions would be pretty sweet. I have the beginnings of something like this working already, although I was going to code it up as a separate npm module. It would be good to do something that is compatible with longjohn and long-stack-traces, too.

I think that's a more common case, so it's not quite there yet.

[technicalpickles]

@jlord have you messed with source maps at all? A big problem we have in hubot land is that stack traces from errors don't correlate to source code lines in coffeescript files (I die a little bit on the inside every time). We could feasibly compile to javascript and sourcemap more directly, but would take a bit of effort as we run everything dynamically with the coffee command.

[jlord]

@technicalpickles No, I haven't worked with source maps. I'm picking some brains at the meetup I'm at right now and it seems one thought coffee would return the error's line in the .js and the coffeescript? Also grunt makes source maps, right?

I still haven't ventured into coffeescript land yet (it's looming close, I know) but I think you can't go wrong with writing small, well named functions and console.log-ing and running before compiling. That's the best I got right now :/

[jlord]

@technicalpickles Browserify will make source maps, too.

21:15 < substack> first way: browserify -c 'coffee -sc' main.coffee > bundle.js
21:15 < substack> second way: npm install coffeeify; browserify -t coffeeify main.coffee > bundle.js
21:16 < substack> second way is probably best
21:16 < substack> the second way works with source maps when you use --debug

[tombell]

coffee does return the line numbers in the .coffee and .js files so maybe source mapping hubot isn't needed?

[tombell]

Closing this as CoffeeScript outputs both line in JavaScript and CoffeeScript.

ReferenceError: foo is not defined
  at Object.<anonymous> (/Users/tom/src/lumberyard/foo.coffee:2:1, <js>:4:3)
  at Object.<anonymous> (/Users/tom/src/lumberyard/foo.coffee:1:1, <js>:6:4)
  at Module._compile (module.js:456:26)

[technicalpickles]

@tombell since when, is it a specific coffee release? I don't think I've seen that output in practice.

[tombell]

It's in whatever the latest is

[tombell]