Remove need for node when generating source maps

[harthur]

I'm using this library in the browser by bundling it with browserify. Everything works fine except when I want to generate source maps. I'll get an error because fs.readFileSync isn't defined. The code path that uses readFile doesn't seem necessary to generate source maps and seems to only be used to apply any original source maps (I'm a bit unclear on that use case):

exports.applySourceMaps = function() {
  Object.keys(this.files).forEach(function(file) {
    var content = this.files[file];
    this.map.setSourceContent(file, content);

    var originalMap = sourceMapResolve.resolveSync(
      content, file, fs.readFileSync);
    if (originalMap) {
      var map = new SourceMapConsumer(originalMap.map);
      var relativeTo = originalMap.sourcesRelativeTo;
      this.map.applySourceMap(map, file, urix(path.dirname(relativeTo)));
    }
  }, this);
};

Right now I'm commenting that part out, but it would be nice to have it work out of the box. If there's any way to put the readFile part behind a conditional, that would be great.

[conradz]

Yeah, I think we should have an option to disable applying original source maps (this is to convert source maps of generated input files, such as Sass, to the output source map). Will work on this.

[ai]

Best settings is no settings :). Maybe if ( fs.readFileSync ) { … } check will be better? Like in PostCSS

[conradz]

The reason I added an option for this is so that (a) behavior does not unexpectedly change when running in browser and (b) this option may be useful for people who do not want this but are running it on Node.

[harthur]

As someone using it, I'm fine with specifying a setting, and to me that seems like it would be better, fwiw.