scss.js

module.exports = {
	extends: [
		'stylelint-config-standard-scss',
		'stylelint-stylistic/config',
	],
	rules: {

		// Disable ESlint as we intentionally break alphabetical order rule here.
		/* eslint-disable sort-keys */

		// Turn `comment-no-empty` back on for empty CSS comments since `scss/comment-no-empty` is turned off later on:
		// https://github.com/stylelint-scss/stylelint-scss/blob/master/src/rules/comment-no-empty/README.md
		'comment-no-empty': true,

		'selector-class-pattern': null, // Disable `stylelint-config-standard-scss`'s `selector-class-pattern` rule.

		// Restrict nesting:
		'selector-nested-pattern': [
			'^&:',
			{
				message: 'Only pseudo-classes and pseudo-elements can be nested (selector-nested-pattern)',
			},
		],

		// Override `stylelint-config-standard-scss`:
		'scss/at-function-pattern': [ // Prefer _ over - for private functions.
			'^(_?[a-z][a-z0-9]*)(-[a-z0-9]+)*$',
			{
				message: 'Expected function name to be kebab-case (private functions must start with _)',
			},
		],
		'scss/at-mixin-argumentless-call-parentheses': 'always', // So it's always written the same way.
		'scss/at-mixin-pattern': [ // Prefer _ over - for private mixins.
			'^(_?[a-z][a-z0-9]*)(-[a-z0-9]+)*$',
			{
				message: 'Expected mixin name to be kebab-case (private mixins must start with _)',
			},
		],
		'scss/comment-no-empty': null, // Allow empty lines in structured block comments.
		'scss/dollar-variable-colon-space-after': 'always-single-line', // Support multi-line variable definitions.
		'scss/dollar-variable-empty-line-before': null, // Turn off to support grouping variables using empty lines.
		'scss/dollar-variable-pattern': [ // Prefer _ over - for private variables.
			'^(_?[a-z][a-z0-9]*)(-[a-z0-9]+)*$',
			{
				message: 'Expected variable to be kebab-case (private variables must start with _)',
			},
		],
		'scss/operator-no-newline-before': null, // Allow operator on new line because multiline expressions are better comprehensible that way.
		'scss/percent-placeholder-pattern': [ // Prefer _ over - for private placeholders.
			'^(_?[a-z][a-z0-9]*)(-[a-z0-9]+)*$',
			{
				message: 'Expected placeholder to be kebab-case (private placeholders must start with _)',
			},
		],

		'stylistic/indentation': 'tab', // Use tabs for indentation.
		'stylistic/string-quotes': 'single', // Use single quotes for strings.
		'stylistic/block-closing-brace-newline-after': [
			'always', {
				ignoreAtRules: ['if', 'else'],
			},
		],

		/* eslint-enable sort-keys */
	},
};