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

const stylelint = require('stylelint');
const { isNumber } = require('stylelint/lib/utils/validateTypes');

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 a single line`,
});


module.exports = stylelint.createPlugin(ruleName, function getPlugin(primaryOption, secondaryOptionObject, context) {
   return function lint(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 nested rules)
            if (rule.nodes.length > primaryOption || !rule.nodes.every((node) => node.type === 'decl')) {
                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
                });
            }
       });
   };
});

module.exports.ruleName = ruleName;
module.exports.messages = messages;