Use Sass preprocessor and Gulp task runner

By default, Magento uses Less for themes styling. But you can use other stylesheet languages that can be compiled (processed) to CSS. For example, Sass is a popular alternative.

If you decide not to use Less and the default Magento UI library, you need to create your own theme from scratch and use an alternative preprocessor. This topic describes how to configure and use the Gulp task runner and the gulp-sass package for the Sass preprocessor.

For details about adding a custom preprocessor, see Add custom CSS preprocessor.

Install Gulp and its Sass preprocessor

In the root of the theme directory, create an empty package.json and copy-paste the following code:

 {
   "author": "Magento Commerce Inc.",
   "description": "Magento node modules dependencies for local development",
   "version": "1.0.0",
   "main": "gulpfile.js",
   "dependencies": {
     "path": "^0.12.7"
   },
   "devDependencies": {
     "gulp": "^3.9.1",
     "gulp-notify": "^3.0.0",
     "gulp-plumber": "^1.1.0",
     "gulp-sass": "^3.1.0"
   },
   "scripts": {
     "test": "echo \"Error: no test specified\" && exit 1"
   }
 }

Install Gulp by running the following command in a command prompt:

npm install --save gulp-install
Add the gulp-sass package for the Sass preprocessor by running the following command:

npm install gulp-sass

Create a theme and add Sass styles

Create a theme, as described in Create a new storefront theme.

Set up a Gulp task for Sass compilation by placing the file with the task code in the root of your theme directory (app/code/frontend/<Vendor>/<theme>). Create an empty app/code/frontend/<Vendor>/<theme>/gulpfile.js file and copy-paste this code into it (no changes needed):

 var gulp         = require('gulp'),
     sass         = require('gulp-sass'),
     plumber      = require('gulp-plumber'),
     notify       = require('gulp-notify');

 var config = {
     src           : './web/css/*.scss',
     dest          : './web/css/'
 };

 // Error message
 var onError = function (err) {
     notify.onError({
         title   : 'Gulp',
         subtitle: 'Failure!',
         message : 'Error: <%= error.message %>',
         sound   : 'Beep'
     })(err);

     this.emit('end');
 };

 // Compile CSS
   gulp.task('styles', function () {
       var stream = gulp
           .src([config.src])
           .pipe(plumber({errorHandler: onError}))
           .pipe(sass().on('error', sass.logError));
    
       return stream
           .pipe(gulp.dest('./web/css/'));
   });

This task uses styles.scss, stored in the app/design/frontend/<Vendor>/<theme>/web/css/ directory, as the source of Sass. It stores the generated CSS in styles.css in the app/code/frontend/<Vendor>/<theme> directory.

Put the source styles.scss file in the app/design/frontend/<Vendor>/<theme>/web/css/ directory.

Declare the resulting CSS file in the default_head_blocks.xml file in the app/design/frontend/<Vendor>/<theme/Magento_Theme/layout/ directory to enable your theme to use the generated CSS. You can create an empty default_head_blocks.xml file and copy the following code:

 <page xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance" xsi:noNamespaceSchemaLocation="urn:magento:framework:View/Layout/etc/page_configuration.xsd">
 	<head>
 	    <css src="css/styles.css"/>
 	</head>
 </page>

To generate CSS, run gulp styles.

Using the @import directive in Sass

In the source .scss files you can use the @import directive, to import other .scss files. You can put the module-related stylesheets in the module directories in the theme, and then include them in the main .scss file. For example, if you create a _catalogstls.scss file for styles of the Magento_Catalog module and put it in app/design/frontend/<Vendor>/<theme>/Magento_Catalog/styles , you can import it using the following notation:

@import '../Magento_Theme/styles/module`

Feb 15th, 2019