@redocly/openapi-core/src/config/rules.ts

See https://github.com/Redocly/openapi-cli

import { RuleSet, OasVersion } from '../oas-types';
import { LintConfig } from './config';
import { notUndefined } from '../utils';

export function initRules<T extends Function, P extends RuleSet<T>>(
  rules: P[],
  config: LintConfig,
  type: 'rules' | 'preprocessors' | 'decorators',
  oasVersion: OasVersion,
) {
  return rules
    .flatMap((ruleset) =>
      Object.keys(ruleset).map((ruleId) => {
        const rule = ruleset[ruleId];

        const ruleSettings =
          type === 'rules'
            ? config.getRuleSettings(ruleId, oasVersion)
            : type === 'preprocessors'
            ? config.getPreprocessorSettings(ruleId, oasVersion)
            : config.getDecoratorSettings(ruleId, oasVersion);

        if (ruleSettings.severity === 'off') {
          return undefined;
        }

        const visitor = rule(ruleSettings);

        return {
          severity: ruleSettings.severity,
          ruleId,
          visitor,
        };
      }),
    )
    .filter(notUndefined);
}