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gulp-postcss

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PostCSS gulp plugin to pipe CSS through several plugins, but parse CSS only once.

Install

$ npm install --save-dev postcss gulp-postcss

Install required postcss plugins separately. E.g. for autoprefixer, you need to install autoprefixer package.

Basic usage

The configuration is loaded automatically from postcss.config.js as described here, so you don't have to specify any options.

var postcss = require('gulp-postcss');
var gulp = require('gulp');

gulp.task('css', function () {
    return gulp.src('./src/*.css')
        .pipe(postcss())
        .pipe(gulp.dest('./dest'));
});

Passing plugins directly

var postcss = require('gulp-postcss');
var gulp = require('gulp');
var autoprefixer = require('autoprefixer');
var cssnano = require('cssnano');

gulp.task('css', function () {
    var plugins = [
        autoprefixer({browsers: ['last 1 version']}),
        cssnano()
    ];
    return gulp.src('./src/*.css')
        .pipe(postcss(plugins))
        .pipe(gulp.dest('./dest'));
});

Using with .pcss extension

For using gulp-postcss to have input files in .pcss format and get .css output need additional library like gulp-rename.

var postcss = require('gulp-postcss');
var gulp = require('gulp');
const rename = require('gulp-rename');

gulp.task('css', function () {
    return gulp.src('./src/*.pcss')
        .pipe(postcss())
        .pipe(rename({
          extname: '.css'
        }))
        .pipe(gulp.dest('./dest'));
});

This is done for more explicit transformation. According to gulp plugin guidelines

Your plugin should only do one thing, and do it well.

Passing additional options to PostCSS

The second optional argument to gulp-postcss is passed to PostCSS.

This, for instance, may be used to enable custom parser:

var gulp = require('gulp');
var postcss = require('gulp-postcss');
var nested = require('postcss-nested');
var sugarss = require('sugarss');

gulp.task('default', function () {
    var plugins = [nested];
    return gulp.src('in.sss')
        .pipe(postcss(plugins, { parser: sugarss }))
        .pipe(gulp.dest('out'));
});

If you are using a postcss.config.js file, you can pass PostCSS options as the first argument to gulp-postcss.

This, for instance, will let PostCSS know what the final file destination path is, since it will be unaware of the path given to gulp.dest():

var gulp = require('gulp');
var postcss = require('gulp-postcss');

gulp.task('default', function () {
    return gulp.src('in.scss')
        .pipe(postcss({ to: 'out/in.css' }))
        .pipe(gulp.dest('out'));
});

Using a custom processor

var postcss = require('gulp-postcss');
var cssnext = require('postcss-cssnext');
var opacity = function (css, opts) {
    css.walkDecls(function(decl) {
        if (decl.prop === 'opacity') {
            decl.parent.insertAfter(decl, {
                prop: '-ms-filter',
                value: '"progid:DXImageTransform.Microsoft.Alpha(Opacity=' + (parseFloat(decl.value) * 100) + ')"'
            });
        }
    });
};

gulp.task('css', function () {
    var plugins = [
        cssnext({browsers: ['last 1 version']}),
        opacity
    ];
    return gulp.src('./src/*.css')
        .pipe(postcss(plugins))
        .pipe(gulp.dest('./dest'));
});

Source map support

Source map is disabled by default, to extract map use together with gulp-sourcemaps.

return gulp.src('./src/*.css')
    .pipe(sourcemaps.init())
    .pipe(postcss(plugins))
    .pipe(sourcemaps.write('.'))
    .pipe(gulp.dest('./dest'));

Advanced usage

If you want to configure postcss on per-file-basis, you can pass a callback that receives vinyl file object and returns { plugins: plugins, options: options }. For example, when you need to parse different extensions differntly:

var gulp = require('gulp');
var postcss = require('gulp-postcss');

gulp.task('css', function () {
    function callback(file) {
        return {
            plugins: [
                require('postcss-import')({ root: file.dirname }),
                require('postcss-modules')
            ],
            options: {
                parser: file.extname === '.sss' ? require('sugarss') : false
            }
        }
    }
    return gulp.src('./src/*.css')
        .pipe(postcss(callback))
        .pipe(gulp.dest('./dest'));
});

The same result may be achieved with postcss-load-config, because it receives ctx with the context options and the vinyl file.

var gulp = require('gulp');
var postcss = require('gulp-postcss');

gulp.task('css', function () {
    var contextOptions = { modules: true };
    return gulp.src('./src/*.css')
        .pipe(postcss(contextOptions))
        .pipe(gulp.dest('./dest'));
});

// postcss.config.js or .postcssrc.js
module.exports = function (ctx) {
    var file = ctx.file;
    var options = ctx;
    return {
        parser: file.extname === '.sss' ? : 'sugarss' : false,
        plugins: {
           'postcss-import': { root: file.dirname }
           'postcss-modules': options.modules ? {} : false
        }
    }
};

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