Add new TypeScript extensions (.mts, .cts) (#728)

config/plugins.cjs

@@ -314,6 +314,8 @@ module.exports = {
 				// TypeScript doesn't yet support using extensions and fails with error TS2691.
 				'.ts': 'never',
 				'.tsx': 'never',
+				'.mts': 'never',
+				'.cts': 'never',
 			},
 		],
 		'n/no-mixed-requires': [

lib/constants.js

@@ -24,6 +24,8 @@ const MERGE_OPTIONS_CONCAT = [
 const TYPESCRIPT_EXTENSION = [
 	'ts',
 	'tsx',
+	'mts',
+	'cts',
 ];
 
 const DEFAULT_EXTENSION = [

readme.md

@@ -315,7 +315,7 @@ Setting this to an object enables the resolver and passes the object as configur
 
 ## TypeScript
 
-XO will automatically lint TypeScript files (`.ts`, `.d.ts` and `.tsx`) with the rules defined in [eslint-config-xo-typescript#use-with-xo](https://github.com/xojs/eslint-config-xo-typescript#use-with-xo).
+XO will automatically lint TypeScript files (`.ts`, `.mts`, `.cts`, `.d.ts` and `.tsx`) with the rules defined in [eslint-config-xo-typescript#use-with-xo](https://github.com/xojs/eslint-config-xo-typescript#use-with-xo).
 
 XO will handle the [@typescript-eslint/parser `project` option](https://github.com/typescript-eslint/typescript-eslint/tree/master/packages/parser#parseroptionsproject) automatically even if you don't have a `tsconfig.json` in your project.
 

test/fixtures/typescript/child/extra-semicolon.cts

@@ -0,0 +1 @@
+console.log('extra-semicolon');;

test/fixtures/typescript/child/extra-semicolon.mts

@@ -0,0 +1 @@
+console.log('extra-semicolon');;

test/lint-files.js

@@ -216,6 +216,24 @@ test.serial('typescript files', async t => {
 		),
 	);
 
+	t.true(
+		hasRule(
+			results,
+			path.resolve('fixtures/typescript/child/extra-semicolon.mts'),
+			'@typescript-eslint/no-extra-semi',
+			rulesMeta,
+		),
+	);
+
+	t.true(
+		hasRule(
+			results,
+			path.resolve('fixtures/typescript/child/extra-semicolon.cts'),
+			'@typescript-eslint/no-extra-semi',
+			rulesMeta,
+		),
+	);
+
 	t.true(
 		hasRule(
 			results,