Update

src/index.ts

@@ -56,11 +56,18 @@ export interface LocalRuleOptions {
 
 export type RuleOptions = Rules & Partial<LocalRuleOptions>;
 
+export interface CustomRule {
+  rule: () => Promise<{
+    default: Rule.RuleModule | ESLintUtils.RuleModule<string, unknown[]>;
+  }>;
+  options?: RuleLevel;
+}
+
 /**
  * ESLint Configuration.
  * @see [ESLint Configuration](https://eslint.org/docs/latest/user-guide/configuring/)
  */
-type Config = Omit<ESLintConfig, 'rules'> & {
+export type InputConfig = Omit<ESLintConfig, 'rules'> & {
   /**
    * Rules.
    * @see [Rules](https://eslint.org/docs/latest/user-guide/configuring/rules)
@@ -68,24 +75,13 @@ type Config = Omit<ESLintConfig, 'rules'> & {
   rules?: RuleOptions;
 
   /**
+   * Glob pattern to find paths to custom rule files in JavaScript or TypeScript.
+   * Note this must be a string literal or an array of string literals since
+   * this is statically analyzed.
    */
-  customRules?: {
-    rule: () => Promise<{
-      default: Rule.RuleModule | ESLintUtils.RuleModule<string, unknown[]>;
-    }>;
-    options?: RuleLevel;
-  }[];
+  customRuleFiles?: string | string[];
 };
 
-export function defineCustomRule<Options extends readonly unknown[]>(
-  rule: () => Promise<{
-    default: Rule.RuleModule | ESLintUtils.RuleModule<string, Options>;
-  }>,
-  options?: Options,
-) {
-  return { rule, options };
-}
-
 /**
  * Returns a ESLint config object.
  *
@@ -104,15 +100,17 @@ export function defineCustomRule<Options extends readonly unknown[]>(
  * Non bundled:
  * 1. [`graphql`](https://the-guild.dev/graphql/eslint/rules)
  */
-export function extendConfig({
-  plugins = [],
-  settings,
-  rules,
-  extends: _extends,
-  overrides,
-  customRules,
-  ...rest
-}: Config = {}): ESLintConfig {
+export function extendConfig(of: InputConfig = {}): ESLintConfig {
+  const {
+    plugins = [],
+    settings,
+    rules,
+    extends: _extends,
+    overrides,
+    customRuleFiles,
+    ...rest
+  } = of;
+
   const hasReact = plugins.includes('react');
   const hasReactRefresh = plugins.includes('react-refresh');
   const hasUnicorn = plugins.includes('unicorn');
@@ -129,7 +127,7 @@ export function extendConfig({
     fs.mkdirSync(ruleDir, { recursive: true });
   }
 
-  const result: Config = {
+  const result: InputConfig = {
     root: true,
     parser: '@typescript-eslint/parser',
     plugins: unique('@typescript-eslint', 'import', 'rules', plugins),

src/local/index.ts

@@ -1,18 +1,13 @@
 import type { ESLint } from 'eslint';
 import * as fs from 'node:fs';
 import { resolve, basename, extname } from 'node:path';
-
-function tryRequire(candidates: string[]) {
-  for (const candidate of candidates) {
-    try {
-      require(candidate);
-      return;
-    } catch {}
-  }
-}
+import { glob } from 'fast-glob';
+import { parseModule } from 'esprima';
+import query from 'esquery';
+import type { Node, Property } from 'estree';
 
 // https://github.com/gulpjs/interpret
-tryRequire([
+const transpilers = [
   'esbin/register',
   'esbuild-register',
   'ts-node/register/transpile-only',
@@ -20,20 +15,63 @@ tryRequire([
   'sucrase/register',
   '@babel/register',
   'coffeescript/register',
-]);
+];
 
-const folders = resolve(process.cwd(), 'eslint-local-rules');
-const files = fs.readdirSync(folders);
+function tryRequire() {
+  for (const candidate of transpilers) {
+    try {
+      require(candidate);
+      return;
+    } catch {}
+  }
+}
+
+const unwrapDefault = <T = any>(module: any): T => module.default ?? module;
 
 const plugin: ESLint.Plugin = {
   rules: {},
 };
 
-for (const file of files) {
-  const module = require(resolve(folders, file));
-  const unwrap = module.default ?? module;
-  const name = unwrap.name ?? basename(file, extname(file));
-  plugin.rules![name] = unwrap;
+function hydrateESTreeNode(n: Node): any {
+  switch (n.type) {
+    case 'Literal':
+      return n.value;
+    case 'ArrayExpression':
+      return n.elements.filter(Boolean).map(hydrateESTreeNode);
+    default:
+      throw new Error(`Unsupported node type: ${n.type}`);
+  }
 }
 
+function parseConfigFile(js: string) {
+  const [node] = query(
+    parseModule(js),
+    'CallExpression[callee.name="extendConfig"] > ObjectExpression > Property[key.name="customRuleFiles"]',
+  );
+  return hydrateESTreeNode((node as Property).value);
+}
+
+function main() {
+  const rootDir = process.cwd();
+
+  const eslintConfigFile = ['.eslintrc.js', '.eslintrc.cjs']
+    .map(file => resolve(rootDir, file))
+    .find(file => fs.existsSync(file));
+
+  if (!eslintConfigFile) return;
+
+  const eslintConfig = fs.readFileSync(eslintConfigFile, 'utf8');
+  const customRuleFiles = parseConfigFile(eslintConfig);
+  if (!customRuleFiles?.length) return;
+
+  tryRequire();
+  for (const file of glob.sync(customRuleFiles)) {
+    const module = unwrapDefault(require(file));
+    const name = module.name ?? basename(file, extname(file));
+    plugin.rules![name] = module;
+  }
+}
+
+main();
+
 export = plugin;

src/presets/local.ts

@@ -1,4 +1,4 @@
-import type { LocalRuleOptions } from '../index';
+import type { LocalRuleOptions } from '..';
 import { error } from '../constants';
 
 export const localRules: Partial<LocalRuleOptions> = {