Problems generating source map files with current Gulp setup - css

Question

I have set up a gulpfile.js in my project. It's working pretty nicely mostly, except when it comes to generating source maps, especially for the LESS files it compiles to CSS.
I have put together a gist which contains all the files in my gulp setup. Please note that other than the gulp file.js itself, all the other files are inside a directory called tasks.
The problems I am having are that
I had to disable the autoprefixer in development because the source maps that were being generated were invalid as the autoprefixer modified the original CSS file after the source maps were generated. To compensate, I have added mixins that add the vendor prefixes during development, and I have to disable those for development and enable the autoprefixer for the production environment.
I am unable to generate a minified CSS file at all if I want source maps. The minification breaks the source maps.
Although I have LiveReload set up, and the associated browser plugins, I cannot get the CSS to get auto-injected into the page as I am making changes.
If anyone can help me structure my gulp file.js to work more efficiently and more effectively, I would appreciate it.
Again, my gulpfile.js and associated tasks are in this gist.

Answer 1

I had to disable the autoprefixer in development because the source maps that were being generated
The docs at https://www.npmjs.com/package/gulp-autoprefixer describe how to use the autoprefixer with gulp-sourcemaps:
gulp.task('default', function () {
return gulp.src('src/**/*.css')
.pipe(sourcemaps.init())
.pipe(autoprefixer())
.pipe(concat('all.css'))
.pipe(sourcemaps.write())
.pipe(gulp.dest('dist'));
});
The above create a new source map for all.css. So you should load the sourcemap generated by the less compiler first, see https://github.com/floridoo/gulp-sourcemaps#load-existing-source-maps
The docs of gulp-minify-css do not describe such an usage, but possible you can do:
gulp.task('minify-css', function() {
gulp.src('./static/css/*.css')
.pipe(sourcemaps.init({loadMaps: true}))
.pipe(minifyCSS({keepBreaks:true}))
.pipe(sourcemaps.write())
.pipe(gulp.dest('./dist/'))
});
Notice that in most cases you minify only your code for production. Development code, which has source maps should not have to be minified.
Since version 2 of Less you can use plugins for the Less compiler. Also gulp-less allows you to use these plugins (programmatic) see also http://lesscss.org/usage/#plugins-using-a-plugin-in-code
Documentation of gulp-less describes how to use the clean-css and autoprefix plugin at https://github.com/plus3network/gulp-less#plugins. Notice that gulp-minify-css is leveraging clean-css's code too.
Also the usage of gulp-less with gulp-sourcemaps to create sourcemaps has been described at https://github.com/plus3network/gulp-less#source-maps
So you should be able to use:
var LessPluginCleanCSS = require("less-plugin-clean-css"),
cleancss = new LessPluginCleanCSS({advanced: true});
var LessPluginAutoPrefix = require('less-plugin-autoprefix'),
autoprefix= new LessPluginAutoPrefix({browsers: ["last 2 versions"]});
gulp.src('./less/**/*.less')
.pipe(sourcemaps.init())
.pipe(less({
plugins: [autoprefix, cleancss]
}))
.pipe(sourcemaps.write('./maps'))
.pipe(gulp.dest('./public/css'));
The above should generate the autoprefixed and minified CSS of your Less source, with CSS sourcemaps written into ./public/css/maps