Add TypeScript support (#426)

Co-authored-by: Sindre Sorhus <sindresorhus@gmail.com>

config/default.tsconfig.json

@@ -0,0 +1,5 @@
+{
+    "include": [
+        "**/*d.ts"
+    ]
+}

lib/constants.js

@@ -16,7 +16,8 @@ const DEFAULT_IGNORES = [
  */
 const MERGE_OPTIONS_CONCAT = ['extends', 'envs', 'globals', 'plugins'];
 
-const DEFAULT_EXTENSION = ['js', 'jsx'];
+const TYPESCRIPT_EXTENSION = ['ts', 'tsx'];
+const DEFAULT_EXTENSION = ['js', 'jsx', ...TYPESCRIPT_EXTENSION];
 
 /**
  * Define the rules config that are overwritten only for specific version of Node.js based on `engines.node` in package.json or the `node-version` option.
@@ -90,7 +91,6 @@ const ENGINE_RULES = {
 };
 
 const PRETTIER_CONFIG_OVERRIDE = {
-	'@typescript-eslint/eslint-plugin': 'prettier/@typescript-eslint',
 	'eslint-plugin-babel': 'prettier/babel',
 	'eslint-plugin-flowtype': 'prettier/flowtype',
 	'eslint-plugin-react': 'prettier/react',
@@ -108,12 +108,26 @@ const CONFIG_FILES = [
 	`${MODULE_NAME}.config.js`
 ];
 
+const TSCONFIG_DEFFAULTS = {
+	compilerOptions: {
+		target: 'es2018',
+		newLine: 'lf',
+		strict: true,
+		noImplicitReturns: true,
+		noUnusedLocals: true,
+		noUnusedParameters: true,
+		noFallthroughCasesInSwitch: true
+	}
+};
+
 module.exports = {
 	DEFAULT_IGNORES,
 	DEFAULT_EXTENSION,
+	TYPESCRIPT_EXTENSION,
 	ENGINE_RULES,
 	PRETTIER_CONFIG_OVERRIDE,
 	MODULE_NAME,
 	CONFIG_FILES,
-	MERGE_OPTIONS_CONCAT
+	MERGE_OPTIONS_CONCAT,
+	TSCONFIG_DEFFAULTS
 };

lib/options-manager.js

@@ -1,6 +1,7 @@
 'use strict';
 const os = require('os');
 const path = require('path');
+const {outputJson, outputJsonSync} = require('fs-extra');
 const arrify = require('arrify');
 const mergeWith = require('lodash/mergeWith');
 const flow = require('lodash/flow');
@@ -12,13 +13,19 @@ const semver = require('semver');
 const {cosmiconfig, cosmiconfigSync, defaultLoaders} = require('cosmiconfig');
 const pReduce = require('p-reduce');
 const micromatch = require('micromatch');
+const JSON5 = require('json5');
+const toAbsoluteGlob = require('to-absolute-glob');
+const tempy = require('tempy');
 const {
 	DEFAULT_IGNORES,
 	DEFAULT_EXTENSION,
+	TYPESCRIPT_EXTENSION,
 	ENGINE_RULES,
 	PRETTIER_CONFIG_OVERRIDE,
-	MODULE_NAME, CONFIG_FILES,
-	MERGE_OPTIONS_CONCAT
+	MODULE_NAME,
+	CONFIG_FILES,
+	MERGE_OPTIONS_CONCAT,
+	TSCONFIG_DEFFAULTS
 } = require('./constants');
 
 const DEFAULT_CONFIG = {
@@ -57,6 +64,8 @@ const mergeFn = (previousValue, value, key) => {
 	}
 };
 
+const isTypescript = file => TYPESCRIPT_EXTENSION.includes(path.extname(file).slice(1));
+
 /**
  * Find config for `lintText`.
  * The config files are searched starting from `options.filename` if defined or `options.cwd` otherwise.
@@ -83,6 +92,15 @@ const mergeWithFileConfig = options => {
 
 	const prettierOptions = options.prettier ? prettier.resolveConfig.sync(searchPath) || {} : {};
 
+	if (options.filename && isTypescript(options.filename)) {
+		const tsConfigExplorer = cosmiconfigSync([], {searchPlaces: ['tsconfig.json'], loaders: {'.json': (_, content) => JSON5.parse(content)}});
+		const {config: tsConfig, filepath: tsConfigPath} = tsConfigExplorer.search(options.filename) || {};
+
+		options.tsConfigPath = tempy.file({name: 'tsconfig.json'});
+		options.ts = true;
+		outputJsonSync(options.tsConfigPath, makeTSConfig(tsConfig, tsConfigPath, [options.filename]));
+	}
+
 	return {options, prettierOptions};
 };
 
@@ -92,38 +110,73 @@ const mergeWithFileConfig = options => {
  */
 const mergeWithFileConfigs = async (files, options) => {
 	options.cwd = path.resolve(options.cwd || process.cwd());
-	return [...(await pReduce(files, async (configs, file) => {
+
+	return Promise.all([...(await pReduce(files.map(file => path.resolve(options.cwd, file)), async (configs, file) => {
 		const configExplorer = cosmiconfig(MODULE_NAME, {searchPlaces: CONFIG_FILES, loaders: {noExt: defaultLoaders['.json']}, stopDir: options.cwd});
 		const pkgConfigExplorer = cosmiconfig('engines', {searchPlaces: ['package.json'], stopDir: options.cwd});
-		const filepath = path.resolve(options.cwd, file);
 
-		const {config: xoOptions, filepath: xoConfigPath} = await configExplorer.search(filepath) || {};
-		const {config: enginesOptions, filepath: enginesConfigPath} = await pkgConfigExplorer.search(filepath) || {};
+		const {config: xoOptions, filepath: xoConfigPath} = await configExplorer.search(file) || {};
+		const {config: enginesOptions, filepath: enginesConfigPath} = await pkgConfigExplorer.search(file) || {};
 
 		let fileOptions = mergeOptions(xoOptions, enginesOptions, options);
 		fileOptions.cwd = xoConfigPath && path.dirname(xoConfigPath) !== fileOptions.cwd ? path.resolve(fileOptions.cwd, path.dirname(xoConfigPath)) : fileOptions.cwd;
 
-		if (!fileOptions.extensions.includes(path.extname(filepath).replace('.', '')) || isFileIgnored(filepath, fileOptions)) {
+		if (!fileOptions.extensions.includes(path.extname(file).replace('.', '')) || isFileIgnored(file, fileOptions)) {
 			// File extension/path is ignored, skip it
 			return configs;
 		}
 
-		const {hash, options: optionsWithOverrides} = applyOverrides(filepath, fileOptions);
+		const {hash, options: optionsWithOverrides} = applyOverrides(file, fileOptions);
+
+		const prettierConfigPath = optionsWithOverrides.prettier ? await prettier.resolveConfigFile(file) : undefined;
+		const prettierOptions = prettierConfigPath ? await prettier.resolveConfig(file, {config: prettierConfigPath}) : {};
 
-		const prettierConfigPath = optionsWithOverrides.prettier ? await prettier.resolveConfigFile(filepath) : undefined;
-		const prettierOptions = prettierConfigPath ? await prettier.resolveConfig(filepath, {config: prettierConfigPath}) : {};
+		let tsConfigPath;
+		if (isTypescript(file)) {
+			let tsConfig;
+			// Override cosmiconfig `loaders` as we look only for the path of tsconfig.json, but not its content
+			const tsConfigExplorer = cosmiconfig([], {searchPlaces: ['tsconfig.json'], loaders: {'.json': (_, content) => JSON5.parse(content)}});
+			({config: tsConfig, filepath: tsConfigPath} = await tsConfigExplorer.search(file) || {});
 
-		const cacheKey = JSON.stringify({xoConfigPath, enginesConfigPath, prettierConfigPath, hash});
+			optionsWithOverrides.tsConfigPath = tsConfigPath;
+			optionsWithOverrides.tsConfig = tsConfig;
+			optionsWithOverrides.ts = true;
+		}
+
+		const cacheKey = JSON.stringify({xoConfigPath, enginesConfigPath, prettierConfigPath, hash, tsConfigPath: fileOptions.tsConfigPath, ts: fileOptions.ts});
 		const cachedGroup = configs.get(cacheKey);
 
 		configs.set(cacheKey, {
-			files: [filepath, ...(cachedGroup ? cachedGroup.files : [])],
+			files: [file, ...(cachedGroup ? cachedGroup.files : [])],
 			options: cachedGroup ? cachedGroup.options : optionsWithOverrides,
 			prettierOptions
 		});
 
 		return configs;
-	}, new Map())).values()];
+	}, new Map())).values()].map(async group => {
+		const {files, options} = group;
+		if (options.ts) {
+			const tsConfigPath = tempy.file({name: 'tsconfig.json'});
+			await outputJson(tsConfigPath, makeTSConfig(options.tsConfig, options.tsConfigPath, files));
+			group.options.tsConfigPath = tsConfigPath;
+			delete group.options.tsConfig;
+		}
+
+		return group;
+	}));
+};
+
+const makeTSConfig = (tsConfig, tsConfigPath, files) => {
+	const config = {files: files.filter(isTypescript)};
+
+	if (tsConfigPath) {
+		config.extends = tsConfigPath;
+		config.include = arrify(tsConfig.include).map(pattern => toAbsoluteGlob(pattern, {cwd: path.dirname(tsConfigPath)}));
+	} else {
+		Object.assign(config, TSCONFIG_DEFFAULTS);
+	}
+
+	return config;
 };
 
 const normalizeOptions = options => {
@@ -191,7 +244,8 @@ const buildConfig = (options, prettierOptions) =>
 	flow(
 		buildXOConfig(options),
 		buildExtendsConfig(options),
-		buildPrettierConfig(options, prettierOptions)
+		buildPrettierConfig(options, prettierOptions),
+		buildTSConfig(options)
 	)(mergeWith(getEmptyOptions(), DEFAULT_CONFIG, normalizeOptions(options), mergeFn));
 
 const buildXOConfig = options => config => {
@@ -212,7 +266,11 @@ const buildXOConfig = options => config => {
 	}
 
 	if (options.space && !options.prettier) {
-		config.rules.indent = ['error', spaces, {SwitchCase: 1}];
+		if (options.ts) {
+			config.rules['@typescript-eslint/indent'] = ['error', spaces, {SwitchCase: 1}];
+		} else {
+			config.rules.indent = ['error', spaces, {SwitchCase: 1}];
+		}
 
 		// Only apply if the user has the React plugin
 		if (options.cwd && resolveFrom.silent(options.cwd, 'eslint-plugin-react')) {
@@ -338,6 +396,27 @@ const mergeWithPrettierConfig = (options, prettierOptions) => {
 	);
 };
 
+const buildTSConfig = options => config => {
+	if (options.ts) {
+		config.baseConfig.extends = config.baseConfig.extends.concat('xo-typescript');
+		config.baseConfig.parser = require.resolve('@typescript-eslint/parser');
+		config.baseConfig.parserOptions = {
+			warnOnUnsupportedTypeScriptVersion: false,
+			ecmaFeatures: {jsx: true},
+			project: options.tsConfigPath
+		};
+
+		if (options.prettier) {
+			config.baseConfig.extends = config.baseConfig.extends.concat('prettier/@typescript-eslint');
+		}
+
+		delete config.tsConfigPath;
+		delete config.ts;
+	}
+
+	return config;
+};
+
 const applyOverrides = (file, options) => {
 	if (options.overrides && options.overrides.length > 0) {
 		const {overrides} = options;

package.json

@@ -1,7 +1,7 @@
 {
 	"name": "xo",
 	"version": "0.26.1",
-	"description": "JavaScript linter with great defaults",
+	"description": "JavaScript/TypeScript linter with great defaults",
 	"license": "MIT",
 	"repository": "xojs/xo",
 	"funding": "https://github.com/sponsors/sindresorhus",
@@ -46,15 +46,20 @@
 		"verify",
 		"enforce",
 		"hint",
-		"simple"
+		"simple",
+		"javascript",
+		"typescript"
 	],
 	"dependencies": {
+		"@typescript-eslint/eslint-plugin": "^2.19.2",
+		"@typescript-eslint/parser": "^2.19.2",
 		"arrify": "^2.0.1",
 		"cosmiconfig": "^6.0.0",
 		"debug": "^4.1.0",
 		"eslint": "^6.8.0",
 		"eslint-config-prettier": "^6.10.0",
 		"eslint-config-xo": "^0.29.0",
+		"eslint-config-xo-typescript": "^0.26.0",
 		"eslint-formatter-pretty": "^3.0.1",
 		"eslint-plugin-ava": "^10.0.1",
 		"eslint-plugin-eslint-comments": "^3.1.2",
@@ -65,9 +70,11 @@
 		"eslint-plugin-promise": "^4.2.1",
 		"eslint-plugin-unicorn": "^16.1.1",
 		"find-cache-dir": "^3.0.0",
+		"fs-extra": "^8.1.0",
 		"get-stdin": "^7.0.0",
 		"globby": "^9.0.0",
 		"has-flag": "^4.0.0",
+		"json5": "^2.1.1",
 		"lodash": "^4.17.15",
 		"meow": "^5.0.0",
 		"micromatch": "^4.0.2",
@@ -79,6 +86,8 @@
 		"resolve-from": "^5.0.0",
 		"semver": "^7.1.3",
 		"slash": "^3.0.0",
+		"tempy": "^0.4.0",
+		"to-absolute-glob": "^2.0.2",
 		"update-notifier": "^4.0.0"
 	},
 	"devDependencies": {
@@ -91,7 +100,8 @@
 		"nyc": "^15.0.0",
 		"pify": "^4.0.0",
 		"proxyquire": "^2.1.3",
-		"temp-write": "^4.0.0"
+		"temp-write": "^4.0.0",
+		"typescript": "^3.7.5"
 	},
 	"eslintConfig": {
 		"extends": "eslint-config-xo"

readme.md

@@ -6,7 +6,7 @@
 	<br>
 </h1>
 
-> JavaScript linter with great defaults
+> JavaScript/TypeScript linter with great defaults
 
 [![Build Status](https://travis-ci.org/xojs/xo.svg?branch=master)](https://travis-ci.org/xojs/xo) [![Coverage Status](https://coveralls.io/repos/github/xojs/xo/badge.svg?branch=master)](https://coveralls.io/github/xojs/xo?branch=master) [![XO code style](https://img.shields.io/badge/code_style-XO-5ed9c7.svg)](https://github.com/xojs/xo) [![Gitter](https://badges.gitter.im/join_chat.svg)](https://gitter.im/xojs/Lobby)
 
@@ -25,8 +25,9 @@ Uses [ESLint](https://eslint.org) underneath, so issues regarding rules should b
 - Beautiful output.
 - Zero-config, but [configurable when needed](#config).
 - Enforces readable code, because you read more code than you write.
-- No need to specify file paths to lint as it lints all JS files except for [commonly ignored paths](#ignores).
+- No need to specify file paths to lint as it lints all JS/TS files except for [commonly ignored paths](#ignores).
 - [Config overrides per files/globs.](#config-overrides)
+- [TypeScript supported by default](#typescript)
 - Includes many useful ESLint plugins, like [`unicorn`](https://github.com/sindresorhus/eslint-plugin-unicorn), [`import`](https://github.com/benmosher/eslint-plugin-import), [`ava`](https://github.com/avajs/eslint-plugin-ava), [`node`](https://github.com/mysticatea/eslint-plugin-node) and more.
 - Automatically enables rules based on the [`engines`](https://docs.npmjs.com/files/package.json#engines) field in your `package.json`.
 - Caches results between runs for much better performance.
@@ -272,7 +273,9 @@ Enforce ES2015+ rules. Disabling this will make it not *enforce* ES2015+ syntax
 
 ### TypeScript
 
-See [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`, `.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.
 
 ### Flow
 

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

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

test/fixtures/typescript/child/package.json

@@ -0,0 +1,5 @@
+{
+    "xo": {
+        "semicolon": false
+    }
+}

test/fixtures/typescript/child/tsconfig.json

@@ -0,0 +1,6 @@
+{
+    "include": [
+        "**/*.ts",
+        "**/*.tsx"
+    ]
+}

test/fixtures/typescript/package.json

@@ -0,0 +1,5 @@
+{
+    "xo": {
+        "space": 4
+    }
+}

test/fixtures/typescript/two-spaces.tsx

@@ -0,0 +1,3 @@
+console.log([
+  2
+]);

test/lint-files.js

@@ -167,3 +167,23 @@ test('find configurations close to linted file', async t => {
 		)
 	);
 });
+
+test('typescript files', async t => {
+	const {results} = await fn.lintFiles('**/*', {cwd: 'fixtures/typescript'});
+
+	t.true(
+		hasRule(
+			results,
+			path.resolve('fixtures/typescript/two-spaces.tsx'),
+			'@typescript-eslint/indent'
+		)
+	);
+
+	t.true(
+		hasRule(
+			results,
+			path.resolve('fixtures/typescript/child/extra-semicolon.ts'),
+			'@typescript-eslint/no-extra-semi'
+		)
+	);
+});

test/lint-text.js

@@ -267,3 +267,13 @@ test('find configurations close to linted file', t => {
 ]);\n`, {filename: 'fixtures/nested-configs/child-override/two-spaces.js'}));
 	t.true(hasRule(results, 'indent'));
 });
+
+test('typescript files', t => {
+	let {results} = fn.lintText('console.log(\'extra-semicolon\');;\n', {filename: 'fixtures/typescript/child/extra-semicolon.ts'});
+	t.true(hasRule(results, '@typescript-eslint/no-extra-semi'));
+
+	({results} = fn.lintText(`console.log([
+  2
+]);`, {filename: 'fixtures/typescript/two-spaces.tsx'}));
+	t.true(hasRule(results, '@typescript-eslint/indent'));
+});