Neutrino Less loader middleware

neutrino-middleware-less-loader is a Neutrino middleware for compiling styles with Less. This middleware only transforms Less to CSS. It is recommended to have @neutrinojs/style-loader (or its substitution) in the configuration to be able to compile Less styles to JavaScript modules.

Requirements

• Node.js v10.13+
• Neutrino v9

Installation

neutrino-middleware-less-loader can be installed from NPM. You should install it to "dependencies" (--save) or "devDependncies" (--save-dev) depending on your goal.

npm install --save-dev neutrino-middleware-less-loader

Usage

neutrino-middleware-less-loader can be consumed from the Neutrino API, middleware, or presets.

In preset

Require this package and plug it into Neutrino. The following shows how you can pass an options object to the middleware, showing the defaults:

let lessLoader = require('neutrino-middleware-less-loader')

neutrino.use(lessLoader({
   include: ['src', 'tests'],
   exclude: [],
   less   : {
      insecure   : true,
      paths      : [],
      rewriteUrls: 'all',
      math       : 'always',
      strictUnits: false,
      globalVars : {},
      modifyVars : {},
      urlArgs    : '',
      plugins    : []
   }
}))

• include: optional array of paths to include in the compilation. Maps to Webpack's rule.include.
• exclude: optional array of paths to exclude from the compilation. Maps to Webpack's rule.include.
• less: optional Less options config that is passed to the loader.

It is recommended to call this middleware after the neutrino.config.module.rule('style') initialization to avoid unexpected overriding. More information about usage of Neutrino middlewares can be found in the documentation.

In neutrinorc

The middleware also may be used together with another presets in Neutrino rc-file, e.g.:

.neutrinorc.js

let web        = require('@neutrino/web')
let lessLoader = require('neutrino-middleware-less-loader')

module.exports = {
   use: [
      web(),
      lessLoader()
   ]
}

Imports paths

The loader can resolve paths in one of two modes: Less or Webpack.

Webpack's resolver is used by default. To use its advantages to look up the modules you need to prepend ~ to the path:

@import "~bootstrap/less/bootstrap";

Otherwise the path will be determined as a relative URL, @import "file" is the same as @import "./file"

If you specify the paths option, the Webpack's resolver will not be used. Modules, that can't be resolved in the local folder, will be searched in the given paths. This is Less' default behavior. paths should be an array with absolute paths:

let lessLoader = require('neutrino-middleware-less-loader')

neutrino.use(lessLoader({
   less: {
      paths: [
         path.resolve(__dirname, 'node_modules')
      ]
   }
}))

Importing variables from JS

LESS files can import variables from JS modules. Example:

vars.js

module.exports = {
   'default-color': 'yellow',
   'border'       : '2px solid red'
}

main.less

require('./vars.js');

@import "./other.less";

.box:extend(.darkgreen) {
  color: @default-color;
  border: @border;
  width: 200px;
  height: 200px;
}

It is recommended to require all JS modules before any @import rules.

Plugins

In order to use LESS plugins, simply set the plugins option:

let CleanCSSPlugin = require('less-plugin-clean-css')

neutrino.use(lessLoader({
   less: {
      plugins: [
         new CleanCSSPlugin({ advanced: true })
      ]
   }
}))

Rules

This is a list of rules that are used by neutrino-middleware-less-loader:

• less: Compiles Less styles to CSS styles. Contains two loaders named: less and less-var.
• style: Only necessary file extension added. CSS loader should be provided to correctly compile styles to JavaScript.