Add support JS objects for extends config option

.changeset/gorgeous-cobras-beam.md

@@ -0,0 +1,5 @@
+---
+"stylelint": minor
+---
+
+Added: support for JS objects with `extends` config option

lib/__tests__/extends.test.mjs

@@ -1,5 +1,6 @@
 import { fileURLToPath } from 'node:url';
 
+import configExtendingWithObject from './fixtures/config-extending-with-object.mjs';
 import readJSONFile from '../testUtils/readJSONFile.mjs';
 import safeChdir from '../testUtils/safeChdir.mjs';
 import standalone from '../standalone.js';
@@ -29,6 +30,19 @@ it('basic extending', async () => {
 	expect(linted.results[0].warnings[0].rule).toBe('block-no-empty');
 });
 
+it('basic extending with object', async () => {
+	const linted = await standalone({
+		code: 'a {}',
+		config: configExtendingWithObject,
+		configBasedir: fixturesPath,
+	});
+
+	expect(typeof linted.output).toBe('string');
+	expect(linted.results).toHaveLength(1);
+	expect(linted.results[0].warnings).toHaveLength(1);
+	expect(linted.results[0].warnings[0].rule).toBe('block-no-empty');
+});
+
 it('recursive extending', async () => {
 	const linted = await standalone({
 		code: 'a {}',

lib/__tests__/fixtures/config-block-no-empty.mjs

@@ -0,0 +1,5 @@
+export default {
+	rules: {
+		'block-no-empty': true,
+	},
+};

lib/__tests__/fixtures/config-extending-with-object.mjs

@@ -0,0 +1,5 @@
+import configBlockNoEmpty from './config-block-no-empty.mjs';
+
+export default {
+	extends: configBlockNoEmpty,
+};

lib/augmentConfig.js

@@ -178,7 +178,13 @@ async function extendConfig(stylelint, config, configDir, rootConfigDir, filePat
 	let resultConfig = originalWithoutExtends;
 
 	for (const extendLookup of normalizedExtends) {
-		const extendResult = await loadExtendedConfig(stylelint, configDir, extendLookup);
+		let extendResult;
+
+		if (typeof extendLookup === 'string') {
+			extendResult = await loadExtendedConfig(stylelint, configDir, extendLookup);
+		} else if (typeof extendLookup === 'object' && extendLookup !== null) {
+			extendResult = { config: extendLookup };
+		}
 
 		if (extendResult) {
 			let extendResultConfig = extendResult.config;