stylelint/lib/utils/isStandardSyntaxUrl.js

A mighty, modern CSS linter.

/* @flow */
'use strict';

const hasLessInterpolation = require('../utils/hasLessInterpolation');
const hasPsvInterpolation = require('../utils/hasPsvInterpolation');
const hasScssInterpolation = require('../utils/hasScssInterpolation');
const hasTplInterpolation = require('../utils/hasTplInterpolation');

/**
 * Check whether a URL is standard
 */
module.exports = function(url /*: string*/) /*: boolean*/ {
	if (url.length === 0) {
		return true;
	}

	// Sass interpolation works anywhere
	if (hasScssInterpolation(url) || hasTplInterpolation(url) || hasPsvInterpolation(url)) {
		return false;
	}

	// Inside `'` and `"` work only LESS interpolation
	if (
		(url[0] === "'" && url[url.length - 1] === "'") ||
		(url[0] === '"' && url[url.length - 1] === '"')
	) {
		if (hasLessInterpolation(url)) {
			return false;
		}

		return true;
	}

	// Less variable works only at the beginning
	// Check is less variable, allow use '@url/some/path'
	// https://github.com/less/less.js/blob/3.x/lib/less/parser/parser.js#L547
	if (url[0] === '@' && /^@@?[\w-]+$/.test(url)) {
		return false;
	}

	// In url without quotes scss variable can be everywhere
	// But in this case it is allowed to use only specific characters
	// Also forbidden "/" at the end of url
	if (
		url.indexOf('$') !== -1 &&
		/^[$\sA-Za-z0-9+-/*_'"/]+$/.test(url) &&
		url[url.length - 1] !== '/'
	) {
		return false;
	}

	return true;
};