Support sourcemaps with browser side compiler

[jadus]

This could be done via data urls :
https://code.google.com/p/chromium/issues/detail?id=285786

[WraithKenny]

Regardless of how to feed the sourcemap to the browser, I'd be handy for the browser compiler (at least optionally when invoked manually) to be able to return a sourcemap file as a string.

I use LESS (in conjunction with CodeMirror) in a WordPress Plugin, and store/return/write files using WP's ajax handlers. If I could get a sourcemap from the browser's less.js, I could handle writing the sourcemap to the correct location, and append the css comment myself. I just need the sourcemap exposed in the browser api.

I'm also trying to get LESS into WP core: http://core.trac.wordpress.org/ticket/22862 for details.

[lukeapage]

Yes, there is an option you will be able to override that is a function
called with the sourcemap output. I will add more details once this works
in the browser version.

[lukeapage]

@WraithKenny
adding this option will work in beta1 & 2 I think.

less.writeSourceMap = function(stringSourceMap) {
}

You can set all the normal sourcemap options lessc has, using the right casing as options on the less object.

[lukeapage]

hrmm, the problem is https://github.com/mozilla/source-map which we use to generate sourcemaps. a) is the license compatible? (I don't know) b) the build can't be easily included into less.js and I'm not sure we would want to just include it.

I have just made a commit allowing the sourcemap to be a data uri, and that works. I've also made the sourcema generator an option so that someone can push it in from the browser. More work needs to be done to decide how this should work.

[jadus]

"SyntaxError: Cannot read property 'SourceMapGenerator' of undefined"
Am I missing something ?

My options are :

            less = {
                env: "development", 
                async: false,
                poll: 2000,
                sourceMap: true
            };

Thanks

[lukeapage]

@jadus I may need to add the option to the env file to get it passed through from the less object to the source map output class.. sorry about that, was in a rush to finish for today

[lukeapage]

I have got data-uris working fine, but chrome isn't liking sourcemaps in inline stylesheets. I have a test case and will raise a bug.

[lukeapage]

Information added here : https://code.google.com/p/chromium/issues/detail?id=285786

I will publish information on how to make this work on the browser once that issue is resolved

[jadus]

Is this working with the last release ?

[lukeapage]

The linked issue prevents it working in chrome. Yes the latest release has a fix in, but to get it working you have to be creative.. I haven't worked out how to include the Mozilla source maps js with less or whether the licences allow it. For lessc the package is included with npm.

[ktiedt]

Just a reference in regards to the potential "legal blocker": http://www.apache.org/legal/3party.html -- If you scroll down you will find a list of Licenses that Apache Foundation projects are allowed to use/include as part of their projects... BSD is one of them, which should make use of the source-map generator that is BSD licensed in an Apache Licensed project safe... -- I am not a lawyer, but that seems like a pretty solid assumption based on the above link.

[englercj]

Hey @lukeapage this is obviously still an issue. Did you ever end up creating a new chromium issue after the one you made was closed? I searched briefly and didn't find it.

This is an annoying issue for me since I got everything working except the Chrome bug not reading the source map.