gulpfile.js

const gulp = require("gulp");
const gulpless = require("gulp-less");
const postcss = require("gulp-postcss");
const debug = require("gulp-debug");
var csso = require("gulp-csso");
const autoprefixer = require("autoprefixer");
const NpmImportPlugin = require("less-plugin-npm-import");

gulp.task("less", function () {
    const plugins = [autoprefixer()];

    return gulp
        .src("styles/themes/*-theme.less")
        .pipe(debug({ title: "Less files:" }))
        .pipe(
            gulpless({
                javascriptEnabled: true,
                plugins: [new NpmImportPlugin({ prefix: "~" })],
            })
        )
        .pipe(postcss(plugins))
        .pipe(
            csso({
                debug: true,
            })
        )
        .pipe(gulp.dest("./public"));
});