ESLint formatter

formatter.js

module.exports = (results) => {
  const byRuleId = results.reduce((map, current) => {
    for (const { column, line, ruleId } of current.messages) {
      if (!map[ruleId]) {
        map[ruleId] = [];
      }

      const occurrence = `${current.filePath}:${line}:${column}`;
      map[ruleId].push(occurrence);
    }

    return map;
  }, {});

  return Object.entries(byRuleId)
    .map(([ruleId, occurrences]) => ({
      ruleId,
      total: occurrences.length,
    }))
    .sort((a, b) => b.total - a.total)
    .map((rule) => `${rule.ruleId}: ${rule.total}`)
    .join("\n");
};