homebrewery/stylelint_plugins/declaration-block-multi-line-min-declarations.js

import stylelint  from 'stylelint';
import { isNumber } from 'stylelint/lib/utils/validateTypes.mjs';

const { report, ruleMessages, validateOptions } = stylelint.utils;
const ruleName = 'naturalcrit/declaration-block-multi-line-min-declarations';
const messages = ruleMessages(ruleName, {
	expected : (decls)=>`Rule with ${decls} declaration${decls == 1 ? '' : 's'} should be single line`,
});

const ruleFunction = (primaryOption, secondaryOptionObject, context)=>{
	return (postcssRoot, postcssResult)=>{

		const validOptions = validateOptions(
			postcssResult,
			ruleName,
			{
				actual   : primaryOption,
				possible : [isNumber],
			}
		);

		if(!validOptions) //If the options are invalid, don't lint
			return;

		const isAutoFixing = Boolean(context.fix);

		postcssRoot.walkRules((rule)=>{ //Iterate CSS rules

			//Apply rule only if all children are decls (no further nested rules)
			if(rule.nodes.length > primaryOption || !rule.nodes.every((node)=>node.type === 'decl'))
				return;

			//Ignore if already one line
			if(!rule.nodes.some((node)=>node.raws.before.includes('\n')) && !rule.raws.after.includes('\n'))
				return;

			if(isAutoFixing) { //We are in “fix” mode
				rule.each((decl)=>decl.raws.before = ' ');
				rule.raws.after = ' ';
			} else {
				report({
					ruleName,
					result  : postcssResult,
					message : messages.expected(rule.nodes.length), // Build the reported message
					node    : rule, // Specify the reported node
					word    : rule.selector, // Which exact word caused the error? This positions the error properly
				});
			}
		});
	};
};

ruleFunction.ruleName = ruleName;
ruleFunction.messages = messages;

export default stylelint.createPlugin(ruleName, ruleFunction);