Gulp 4 config file for Jekyll

gulpfile.js

const path        = require('path');
const child       = require('child_process');
const browserSync = require('browser-sync');
const browserify  = require('browserify');
const watchify    = require('watchify');
const log         = require('fancy-log');
const source      = require('vinyl-source-stream');
const streamify   = require('gulp-streamify');

const gulp        = require('gulp');
const sass        = require('gulp-sass');
const uglify      = require('gulp-uglify');
const htmlmin     = require('gulp-htmlmin');
const cleanCSS    = require('gulp-clean-css');
const prefix      = require('gulp-autoprefixer');

//
// Source and distribute folders paths
//
const srcDir      = 'src/';
const srcStyle    = srcDir + '_scss/';
const srcScripts  = srcDir + '_js/';

const distDir     = 'dist/';
const distStyle   = distDir + 'css/';
const distScripts = distDir + 'js/';

//
// Main source files
//
const styleMain   = 'main.scss';
const scriptMain  = 'main.js';


const jekyll = done => {
    let productionEnv = process.env;
    productionEnv.JEKYLL_ENV = 'production';

    const jekyll = child.spawn('jekyll' , ['build'], { env: productionEnv });

    const jekyllLogger = (buffer) => {
        buffer.toString()
            .split(/\n/)
            .forEach((message) => log('Jekyll: ' + message));
    };

    jekyll.stdout.on('data', jekyllLogger);
    jekyll.stderr.on('data', jekyllLogger);
    jekyll.on('close', done);
};

const scripts = () => {
    const opts = {
        entries: srcScripts + scriptMain,
        debug: true,
    };
    const b = watchify(browserify(opts));

    return b.bundle()
        .on('error', log.error.bind(log, 'Browserify Error'))
        .pipe(source('bundle.js'))
        .pipe(streamify(uglify()))
        .pipe(browserSync.reload({stream: true}))
        .pipe(gulp.dest(distScripts))
        .on('error', log);
};

const styles = () => {
    return gulp.src(srcStyle + styleMain)
        .pipe(sass({
            style: 'compressed',
            includePaths: ['scss'],
            onError: browserSync.notify
        }))
        .pipe(prefix(['last 15 versions', '> 1%', 'ie 8', 'ie 7'], { cascade: true }))
        .pipe(cleanCSS())
        .pipe(browserSync.reload({stream: true}))
        .pipe(gulp.dest(distStyle))
        .on('error', log);
};

const html = () => {
    return gulp.src([
            path.join(distDir, '*.html'),
            path.join(distDir, '*/*.html')
        ])
        .pipe(htmlmin({collapseWhitespace: true}))
        .pipe(gulp.dest(distDir))
        .on('error', log);
};

const browserSyncTask = done => {
    browserSync({
        open: false,
        logFileChanges: true,
        server: {
            baseDir: './dist'
        }
    });
    done();
};

const build = done => {
    gulp.series(jekyll, gulp.parallel(styles, scripts, html))(done)
};

const browserSyncReload = done => {
    browserSync.reload({stream:true});
    done();
};

const watcher = done => {
    gulp.watch([
        path.join(srcStyle, '*.?(s)css'),
        path.join(srcStyle, '**/*.?(s)css'),
    ], gulp.series(styles));
    gulp.watch([
        path.join(srcScripts, '*.js'),
        path.join(srcScripts, '**/*.js'),
    ], gulp.series(scripts));
    gulp.watch([
        path.join(srcDir, '_layouts/*.html'),
        path.join(srcDir, '_includes/*'),
        path.join(srcDir, '_posts/*'),
        path.join(srcDir, '*.html'),
        path.join(srcDir, '*.md'),
    ], gulp.series(build, browserSyncReload));
    done();
};

exports.build = build;
exports.default = gulp.series(build, browserSyncTask, watcher);