Helpers for modifying/patching parts of eslint-config-sheriff rules without adding overrides

patch-sheriff-config.ts

import type { Linter } from 'eslint';
import { sheriff } from 'eslint-config-sheriff';

type SheriffConfig = ReturnType<typeof sheriff>;
type ArrayItem<T> = T extends (infer U)[] ? U : never;
type SheriffConfigItem = ArrayItem<SheriffConfig>;

type RuleName = string;
type RuleUpdater =
  | Linter.RuleEntry
  | ((ruleValue: Linter.RuleEntry) => Linter.RuleEntry);

export function updateRule(
  config: SheriffConfigItem,
  ruleName: RuleName,
  updaterOrValue: RuleUpdater,
): SheriffConfigItem {
  const updatedConfig = { ...config };

  if (config.rules) {
    updatedConfig.rules = { ...config.rules };
  }

  if (!updatedConfig.rules?.[ruleName]) {
    return config;
  }

  if (typeof updaterOrValue === 'function') {
    updatedConfig.rules[ruleName] = updaterOrValue(
      updatedConfig.rules[ruleName],
    );
  } else {
    updatedConfig.rules[ruleName] = updaterOrValue;
  }

  return updatedConfig;
}

export function updateRules(
  config: SheriffConfigItem,
  rules: Record<RuleName, RuleUpdater>,
): SheriffConfigItem {
  let updatedConfig = { ...config };

  for (const [ruleName, updaterOrValue] of Object.entries(rules)) {
    updatedConfig = updateRule(config, ruleName, updaterOrValue);
  }

  return updatedConfig;
}

/**
 * Modify configurations of existing Sheriff rules.
 * This enables overriding only specific rule options without duplicating the entire RuleEntry and related file filters.
 */
export function modifySheriffConfig(
  config: SheriffConfig,
  rules: Record<RuleName, RuleUpdater>,
): SheriffConfig {
  return config.map((configItem) => updateRules(configItem, rules));
}

export function patchSheriffConfig(config: SheriffConfig): SheriffConfig {
  return modifySheriffConfig(config, {
    'vitest/consistent-test-it': [
      'error',
      {
        fn: 'test',
        withinDescribe: 'it',
      },
    ],
  });
}