now-deployment/node_modules/now/dist/util/alias/validate-path-alias-rules.ts

import { RulesFileValidationError } from '../errors-ts';
import { PathRule } from '../../types';

export default function validatePathAliasRules(
  location: string,
  rules: PathRule[]
) {
  if (!Array.isArray(rules)) {
    return new RulesFileValidationError(location, 'rules must be an array');
  }
  if (rules.length === 0) {
    return new RulesFileValidationError(location, 'empty rules');
  }

  for (const rule of rules) {
    if (!(rule instanceof Object)) {
      return new RulesFileValidationError(
        location,
        'all rules must be objects'
      );
    }
    if (!rule.dest) {
      return new RulesFileValidationError(
        location,
        'all rules must have a dest field'
      );
    }
  }
}