feat: improve type suggestions with specific defineFlatConfig

package.json

@@ -73,6 +73,7 @@
     "eslint-plugin-unicorn": "~44.0.2",
     "eslint-plugin-vue": "~9.6.0",
     "eslint-plugin-vue-pug": "~0.5.4",
+    "expect-type": "~0.15.0",
     "json-schema": "~0.4.0",
     "json-schema-to-typescript": "~11.0.2",
     "prettier": "2.7.1",

src/flat-config/index.d.ts

@@ -1,6 +1,5 @@
 import type { ESLint, Linter } from 'eslint';
 import type { Rules } from '../rules';
-import type { LiteralUnion } from '../utility-types';
 import type { LanguageOptions } from './language-options';
 import type { LinterOptions } from './linter-options';
 
@@ -63,12 +62,9 @@ export interface FlatESLintConfigItem {
  *
  * @see [Using predefined configurations](https://eslint.org/docs/latest/user-guide/configuring/configuration-files-new#using-predefined-configurations)
  */
-export type PredefinedConfig = LiteralUnion<
-  'eslint:recommended' | 'eslint:all'
->;
+export type PredefinedConfig = 'eslint:recommended' | 'eslint:all';
 
 export type FlatESLintConfig = FlatESLintConfigItem | PredefinedConfig;
-export type FlatESLintConfigs = Array<FlatESLintConfig>;
 
 export * from './language-options';
 export * from './linter-options';

src/index.d.ts

@@ -1,5 +1,5 @@
 import type { ESLintConfig } from './config';
-import type { FlatESLintConfig, FlatESLintConfigs } from './flat-config';
+import type { FlatESLintConfig } from './flat-config';
 
 /**
  * Define an ESLint config.
@@ -17,7 +17,7 @@ export function defineConfig(config: ESLintConfig): ESLintConfig;
  * @param config an item of Flat ESLint config.
  * @returns an item of Flat ESLint config.
  */
-export function defineConfig(config: FlatESLintConfig): FlatESLintConfig;
+export function defineFlatConfig(config: FlatESLintConfig): FlatESLintConfig;
 
 /**
  * Define a flat ESLint config.
@@ -27,7 +27,9 @@ export function defineConfig(config: FlatESLintConfig): FlatESLintConfig;
  * @param config Flat ESLint config.
  * @returns Flat ESLint config.
  */
-export function defineConfig(config: FlatESLintConfigs): FlatESLintConfigs;
+export function defineFlatConfig(
+  config: readonly FlatESLintConfig[],
+): FlatESLintConfig[];
 
 export * from './config';
 export * from './flat-config';

src/index.js

@@ -2,15 +2,7 @@
 
 exports.__esModule = true;
 exports.defineConfig = void 0;
+exports.defineFlatConfig = void 0;
 
-/**
- * Define an ESLint config.
- *
- * @param config ESLint config.
- * @returns ESLint config.
- */
-function defineConfig(config) {
-  return config;
-}
-
-exports.defineConfig = defineConfig;
+exports.defineConfig = (config) => config;
+exports.defineFlatConfig = (config) => config;

src/index.mjs

@@ -1,9 +1,7 @@
-/**
- * Define an eslint config.
- *
- * @param config Eslint config.
- * @returns Eslint config.
- */
 export function defineConfig(config) {
   return config;
 }
+
+export function defineFlatConfig(config) {
+  return config;
+}

tests/define.test.ts

@@ -0,0 +1,49 @@
+import { expectTypeOf } from 'expect-type';
+import { describe, test } from 'vitest';
+import type { ESLintConfig, FlatESLintConfig } from '../src';
+import { defineConfig, defineFlatConfig } from '../src';
+
+describe('define', () => {
+  test('define empty config', () => {
+    expectTypeOf(defineConfig({})).toEqualTypeOf<ESLintConfig>();
+  });
+
+  test('define ESLint config', () => {
+    expectTypeOf(
+      defineConfig({
+        env: {},
+        extends: [],
+        rules: {},
+      }),
+    ).toEqualTypeOf<ESLintConfig>();
+  });
+
+  test('define an item of flat ESLint config', () => {
+    expectTypeOf(
+      defineFlatConfig({
+        ignores: [],
+        plugins: {},
+        rules: {},
+      }),
+    ).toEqualTypeOf<FlatESLintConfig>();
+  });
+
+  test('define predefined flat ESLint config', () => {
+    expectTypeOf(
+      defineFlatConfig('eslint:recommended'),
+    ).toEqualTypeOf<FlatESLintConfig>();
+  });
+
+  test('define flat ESLint config', () => {
+    expectTypeOf(
+      defineFlatConfig([
+        'eslint:recommended',
+        {
+          ignores: [],
+          plugins: {},
+          rules: {},
+        },
+      ]),
+    ).toEqualTypeOf<FlatESLintConfig[]>();
+  });
+});