Css minification not working (gulp + cssnano)

Question

I have a very basic gulpfile set up like this:

'use strict';

var gulp = require('gulp');
var sass = require('gulp-sass');
var notify = require('gulp-notify');
var browserSync = require('browser-sync').create();
var useref = require('gulp-useref');
var cssnano = require('gulp-cssnano');
var uglify = require('gulp-uglify');
var gulpIf = require('gulp-if');

/*----------  Config settings  ----------*/

var config = {
    devPath: './app/',
    publicPath: './dist/',
    sassDir: 'sass/',
    jsDir: 'js/',
    cssDir: 'css/',
    fontDir: 'fonts/',
    moduleDir: './node_modules',
}

/*----------  Define tasks  ----------*/

gulp.task('browserSync', function() {
    var htmlDir = config.publicPath;

    browserSync.init({
        server: {
            baseDir: htmlDir
        },
    })
})

gulp.task('sassTask', function () {
    var sassFiles = config.devPath + config.sassDir + '/*.scss';
    var destDir = config.publicPath + config.cssDir;

    return gulp.src(sassFiles)
        .pipe(sass()
            .on("error", notify.onError(function (error) {
                return "Error: " + error.message;
            })))
        .pipe(gulp.dest(destDir));
});

gulp.task('useref', function(){
    var htmlFiles = config.devPath + '*.html';
    var destDir = config.publicPath;

    return gulp.src(htmlFiles)
        .pipe(useref())
        // Minifies only if it's a JavaScript file
        .pipe(gulpIf('*.js', uglify()))
        // Minifies only if it's a CSS file
        .pipe(gulpIf('*.css', cssnano()))
        .pipe(gulp.dest(destDir))
        .pipe(browserSync.reload({
            stream: true
        }));
});

gulp.task('js', function() {
    var jsFiles = config.devPath + config.jsDir + '**/*.js';    // All files
    var destDir = config.publicPath + config.jsDir;

    return gulp.src(jsFiles)
                .pipe(gulp.dest(destDir));
});

gulp.task('fonts', function() {
    var fontFiles = config.devPath + config.fontDir + '**/*';   // All files
    var destDir = config.publicPath + config.fontDir;

    return gulp.src(fontFiles)
                .pipe(gulp.dest(destDir));
});

/*----------  Define watch  ----------*/

gulp.task('watch', ['browserSync', 'sassTask', 'js', 'useref', 'fonts'], function () {
    var sassFiles = config.devPath + config.sassDir + '**/*.scss';
    var jsFiles = config.devPath + config.jsDir + '**/*.js';
    var htmlFiles = config.devPath + '*.html';
    var fontFiles = config.devPath + config.fontDir + '**/*';

    gulp.watch(sassFiles, ['sassTask', 'useref']);
    gulp.watch(jsFiles, ['js', 'useref']);
    gulp.watch(htmlFiles, ['useref']);
    gulp.watch(fontFiles, ['fonts']);
});

gulp.task('default', ['browserSync', 'sassTask', 'useref', 'fonts']);

Everything is working fine when running 'gulp watch' (browser sync, sass, etc.) but the css minification isn't. The outputfile 'style.css' in the dist/css folder isn't minified. What am I doing wrong? Am I missing a module? Thanks in advance for your help.

My file structure:

├───app
│   ├───fonts
│   ├───js
│   └───sass
├───dist
│   ├───css
│   │   └───vendor
│   ├───fonts
│   ├───img
│   │   ├───common
│   │   └───layout
│   └───js
│       └───vendor

Answer 1

You should change this sub-task as follows:

gulp.task('useref', function(){
    var files = [
        config.devPath + '*.html', 
        config.publicPath + config.jsDir + '*.js',
        config.publicPath + config.cssDir + '*.css'
    ];
    var destDir = config.publicPath;

    return gulp.src(files)
        // Run useref only if it’s an HTML file
        .pipe(gulpIf('*.html', useref()))
        // Minifies only if it's a JavaScript file
        .pipe(gulpIf('*.js', uglify()))
        // Minifies only if it's a CSS file
        .pipe(gulpIf('*.css', cssnano()))
        .pipe(gulp.dest(destDir))
        .pipe(browserSync.reload({
            stream: true
        }));
});

The first change is in the htmlFiles (i changes it to files for convenience). You need to change the file pattern to match al desired files: *.html, *.js and *.css in the different folders used as sources, because you want to modify the generated files. Using node glob patterns you can easily match the files by file extension passing an array of file patterns, to match different files in different folders..

Then just add a gulpIf condition for the html files tasks to filter the desired file type (you already have the filter function for the other file types).

Hope it helps.