postcss-less

What is postcss-less?

The postcss-less npm package is a tool that allows you to parse LESS syntax with PostCSS, enabling you to use PostCSS plugins with LESS files. It is a syntax plugin for PostCSS, a tool for transforming styles with JavaScript plugins.

What are postcss-less's main functionalities?

Parsing LESS Syntax

This feature allows you to parse LESS files using PostCSS by specifying the postcss-less syntax. This is useful for applying PostCSS plugins to LESS files.

const postcss = require('postcss');
const postcssLess = require('postcss-less');

postcss().process(lessCode, { syntax: postcssLess }).then(result => {
  console.log(result.css);
});

Stringifying LESS

This feature enables you to convert a PostCSS AST (Abstract Syntax Tree) back into a LESS string. This is useful when you want to generate LESS code after manipulating the AST.

const postcss = require('postcss');
const postcssLess = require('postcss-less');

const root = postcss.parse(lessCode, { syntax: postcssLess });
const less = root.toString(postcssLess);

Other packages similar to postcss-less

postcss-scss

This package is similar to postcss-less but is designed to work with SCSS syntax. It allows you to use PostCSS plugins with SCSS files.

postcss-sass

Similar to postcss-less, postcss-sass enables you to parse SASS syntax with PostCSS. It is another syntax plugin for PostCSS that targets SASS files instead of LESS.

postcss-styl

This package is a PostCSS syntax for parsing Stylus. Like postcss-less, it allows you to use PostCSS plugins with Stylus files, providing similar functionality for a different preprocessor language.

README

PostCSS LESS Syntax - Work in Progress

This project is not stable and is in development. If you'd like to contribute, please submit a Pull Request.

A LESS parser for PostCSS.

This module does not compile LESS. It simply parses mixins and variables so that PostCSS plugins can then transform LESS source code alongside CSS.

Use Cases

• lint your LESS code with a plugin such as Stylelint.
• apply PostCSS transformations (such as Autoprefixer) directly to the LESS source code

Usage

LESS Transformations

The main use case of this plugin is to apply PostCSS transformations directly to LESS source code. For example, if you ship a theme written in LESS and need Autoprefixer to add the appropriate vendor prefixes to it.

const syntax = require('postcss-less');
postcss(plugins).process(lessText, { syntax: syntax }).then(function (result) {
    result.content // LESS with transformations
});

Parser options

• mixinsAsAtRules - parse all mixins as AtRule nodes

• innerMixinsAsRules - parse all inner mixins as Rule nodes

It makes sense to use this option with mixinsAsAtRules if you want to parse mixins on the root level as AtRule and all inner mixins as Rule nodes.

Options help you to tell postcss-less to fake LESS-specific syntax. For example, Stylelint requires the next options:

const syntax = require('postcss-less');
const postcssParserOptions = { 
    syntax: syntax, 
    mixinsAsAtRules: true,
    innerMixinsAsRules: true
};

postcss().process(lessText, postcssParserOptions).then(function (result) {
    result.content // LESS with transformations
});

Inline Comments for PostCSS

This module also enables parsing of single-line comments in CSS source code.

:root {
    // Main theme color
    --color: red;
}

Note that you don't need a special stringifier to handle the output; the default one will automatically convert single line comments into block comments.

Restrictions

Skipping mixins without body

postcss-less parses all mixins without body as custom nodes with specifix types:

.foo(); //'mixin-function' node
.foo; // 'mixin-inline' node

PostCSS skips all these mixins, so you won't have them in the result.

Skipping inner extend

postcss-less parses nested &:extend constructions as custom nodes with type nested-extend. PostCSS doesn't parse this node type and you won't have these constructions in the result.

Contribution

Please, check our guidelines: CONTRIBUTING.md

Attribution

This module is based on the work of postcss-scss library and includes the LESS parser efforts of github:gilt/postcss-less