Enforce rules based on "engines" field in package.json (#281)

config/plugins.js

@@ -31,8 +31,6 @@ module.exports = {
 	rules: {
 		'no-use-extend-native/no-use-extend-native': 'error',
 		'promise/param-names': 'error',
-		// Enable this sometime in the future when Node.js has async/await support
-		// 'promise/prefer-await-to-then': 'error',
 		'promise/no-return-wrap': ['error', {allowReject: true}],
 		'promise/no-return-in-finally': 'error',
 		'import/default': 'error',
@@ -81,6 +79,9 @@ module.exports = {
 		// Disabled as the rule doesn't exclude scripts executed with `node` but not referenced in "bin". See https://github.com/mysticatea/eslint-plugin-node/issues/96
 		// 'node/shebang': 'error',
 		'node/no-deprecated-api': 'error',
-		'node/exports-style': ['error', 'module.exports']
+		'node/exports-style': ['error', 'module.exports'],
+		// Disabled by default (overrides `plugin:unicorn/recommended`), will be enabled if supported by the Node.js version
+		'unicorn/prefer-spread': 'off',
+		'unicorn/no-new-buffer': 'off'
 	}
 };

lib/options-manager.js

@@ -8,6 +8,7 @@ const pathExists = require('path-exists');
 const pkgConf = require('pkg-conf');
 const resolveFrom = require('resolve-from');
 const prettier = require('prettier');
+const semver = require('semver');
 
 const DEFAULT_IGNORE = [
 	'**/node_modules/**',
@@ -42,6 +43,46 @@ const DEFAULT_CONFIG = {
 	}
 };
 
+/**
+ * Define the rules that are enabled only for specific version of Node, based on `engines.node` in package.json or the `node-version` option.
+ *
+ * The keys are rule names and the values are an Object with a valid semver (`4.0.0` is valid `4` is not) as keys and the rule configuration as values.
+ * Each entry define the rule configuration and the minimum Node version for which to set it.
+ * The entry with the highest version that is compliant with the `engines.node`/`node-version` range will be used.
+ *
+ * @type {Object}
+ *
+ * @example
+ * ```javascript
+ * {
+ * 	'plugin/rule': {
+ * 		'6.0.0': ['error', {prop: 'node-6-conf'}],
+ *		'8.0.0': ['error', {prop: 'node-8-conf'}]
+ * 		}
+ * }
+ *```
+ * With `engines.node` set to `>=4` the rule `plugin/rule` will not be used.
+ * With `engines.node` set to `>=6` the rule `plugin/rule` will be used with the config `{prop: 'node-6-conf'}`.
+ * With `engines.node` set to `>=8` the rule `plugin/rule` will be used with the config `{prop: 'node-8-conf'}`.
+ */
+const ENGINE_RULES = {
+	'promise/prefer-await-to-then': {
+		'7.6.0': 'error'
+	},
+	'prefer-rest-params': {
+		'6.0.0': 'error'
+	},
+	'unicorn/prefer-spread': {
+		'5.0.0': 'error'
+	},
+	'prefer-destructuring': {
+		'6.0.0': ['error', {array: true, object: true}, {enforceForRenamedProperties: true}]
+	},
+	'unicorn/no-new-buffer': {
+		'5.10.0': 'error'
+	}
+};
+
 // Keep the same behaviour in mergeWith as deepAssign
 const mergeFn = (prev, val) => {
 	if (Array.isArray(prev) && Array.isArray(val)) {
@@ -88,7 +129,8 @@ const mergeWithPkgConf = opts => {
 	opts = Object.assign({cwd: process.cwd()}, opts);
 	opts.cwd = path.resolve(opts.cwd);
 	const conf = pkgConf.sync('xo', {cwd: opts.cwd, skipOnFalse: true});
-	return Object.assign({}, conf, opts);
+	const engines = pkgConf.sync('engines', {cwd: opts.cwd});
+	return Object.assign({}, conf, {engines}, opts);
 };
 
 const normalizeSpaces = opts => {
@@ -129,6 +171,17 @@ const buildConfig = opts => {
 	);
 	const spaces = normalizeSpaces(opts);
 
+	if (opts.engines && opts.engines.node && semver.validRange(opts.engines.node)) {
+		for (const rule of Object.keys(ENGINE_RULES)) {
+			// Use the rule value for the highest version that is lower or equal to the oldest version of Node supported
+			for (const minVersion of Object.keys(ENGINE_RULES[rule]).sort(semver.compare)) {
+				if (!semver.intersects(opts.engines.node, `<${minVersion}`)) {
+					config.rules[rule] = ENGINE_RULES[rule][minVersion];
+				}
+			}
+		}
+	}
+
 	if (opts.space) {
 		config.rules.indent = ['error', spaces, {SwitchCase: 1}];
 

main.js

@@ -4,6 +4,7 @@ const updateNotifier = require('update-notifier');
 const getStdin = require('get-stdin');
 const meow = require('meow');
 const formatterPretty = require('eslint-formatter-pretty');
+const semver = require('semver');
 const openReport = require('./lib/open-report');
 const xo = require('.');
 
@@ -21,6 +22,7 @@ const cli = meow(`
 	  --space           Use space indent instead of tabs  [Default: 2]
 	  --no-semicolon    Prevent use of semicolons
 	  --prettier        Conform to Prettier code style
+	  --node-version    Range of Node.js version to support
 	  --plugin          Include third-party plugins  [Can be set multiple times]
 	  --extend          Extend defaults with a custom config  [Can be set multiple times]
 	  --open            Open files with issues in your editor
@@ -76,6 +78,9 @@ const cli = meow(`
 		prettier: {
 			type: 'boolean'
 		},
+		nodeVersion: {
+			type: 'string'
+		},
 		plugin: {
 			type: 'string'
 		},
@@ -136,6 +141,17 @@ if (input[0] === '-') {
 	input.shift();
 }
 
+if (opts.nodeVersion) {
+	if (opts.nodeVersion === 'false') {
+		opts.engines = false;
+	} else if (semver.validRange(opts.nodeVersion)) {
+		opts.engines = {node: opts.nodeVersion};
+	} else {
+		console.error('The `node-engine` option must be a valid semver range (for example `>=4`)');
+		process.exit(1);
+	}
+}
+
 if (opts.init) {
 	require('xo-init')();
 } else if (opts.stdin) {

package.json

@@ -97,6 +97,7 @@
 		"prettier": "~1.10.2",
 		"resolve-cwd": "^2.0.0",
 		"resolve-from": "^4.0.0",
+		"semver": "^5.4.1",
 		"slash": "^1.0.0",
 		"update-notifier": "^2.1.0",
 		"xo-init": "^0.6.0"

readme.md

@@ -27,6 +27,7 @@ Uses [ESLint](http://eslint.org) underneath, so issues regarding rules should be
 - No need to specify file paths to lint as it lints all JS files except for [commonly ignored paths](#ignores).
 - [Config overrides per files/globs.](#config-overrides)
 - 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.
 - Super simple to add XO to a project with `$ xo --init`.
 - Fix many issues automagically with `$ xo --fix`.
@@ -61,6 +62,7 @@ $ xo --help
     --space           Use space indent instead of tabs  [Default: 2]
     --no-semicolon    Prevent use of semicolons
     --prettier        Conform to Prettier code style
+    --node-version    Range of Node.js version to support
     --plugin          Include third-party plugins  [Can be set multiple times]
     --extend          Extend defaults with a custom config  [Can be set multiple times]
     --open            Open files with issues in your editor
@@ -206,6 +208,14 @@ Default: `false`
 
 Format code with [Prettier](https://github.com/prettier/prettier). The [Prettier options](https://prettier.io/docs/en/options.html) will be read from the [Prettier config](https://prettier.io/docs/en/configuration.html)
 
+### nodeVersion
+
+Type: `string`, `boolean`<br>
+Default: Value of the `engines.node` key in the project `package.json`
+
+Enable rules specific to the Node.js versions within the configured range.
+If set to `false`, no rules specific to a Node.js version will be enabled.
+
 ### plugins
 
 Type: `Array`
@@ -303,6 +313,25 @@ If you have a directory structure with nested `package.json` files and you want
 
 Put a `package.json` with your config at the root and add `"xo": false` to the `package.json` in your bundled packages.
 
+### Transpilation
+
+If some files in your project are transpiled in order to support an older Node.js version, you can use the [config overrides](#config-overrides) option to set a specific [`nodeVersion`](#nodeversion) target for these files.
+
+For example, if your project targets Node.js 4 (your `package.json` is configured with `engines.node` set to `>=4`) and you are using [AVA](https://github.com/avajs/ava), then your test files are automatically transpiled. You can override `nodeVersion` for the tests files:
+
+```json
+{
+	"xo": {
+		"overrides": [
+			{
+				"files": "{test,tests,spec,__tests__}/**/*.js",
+				"nodeVersion": ">=9"
+			}
+		]
+	}
+}
+```
+
 
 ## FAQ
 

test/fixtures/engines/package.json

@@ -0,0 +1,7 @@
+{
+	"name": "application-name",
+	"version": "0.0.1",
+	"engines": {
+		"node": ">=6"
+	}
+}

test/main.js

@@ -94,3 +94,9 @@ test('init option', async t => {
 	const packageJson = fs.readFileSync(filepath, 'utf8');
 	t.deepEqual(JSON.parse(packageJson).scripts, {test: 'xo'});
 });
+
+test('invalid node-engine option', async t => {
+	const filepath = await tempWrite('console.log()\n', 'x.js');
+	const err = await t.throws(main(['--node-version', 'v', filepath]));
+	t.is(err.code, 1);
+});

test/options-manager.js

@@ -4,6 +4,7 @@ import proxyquire from 'proxyquire';
 import parentConfig from './fixtures/nested/package';
 import childConfig from './fixtures/nested/child/package';
 import prettierConfig from './fixtures/prettier/package';
+import enginesConfig from './fixtures/engines/package';
 
 process.chdir(__dirname);
 
@@ -138,6 +139,88 @@ test('buildConfig: prettier: true, esnext: false', t => {
 	}]);
 });
 
+test('buildConfig: engines: undefined', t => {
+	const config = manager.buildConfig({});
+
+	// Do not include any Node.js version specific rules
+	t.is(config.rules['prefer-spread'], undefined);
+	t.is(config.rules['prefer-rest-params'], undefined);
+	t.is(config.rules['prefer-destructuring'], undefined);
+	t.is(config.rules['promise/prefer-await-to-then'], undefined);
+});
+
+test('buildConfig: engines: false', t => {
+	const config = manager.buildConfig({engines: false});
+
+	// Do not include any Node.js version specific rules
+	t.is(config.rules['prefer-spread'], undefined);
+	t.is(config.rules['prefer-rest-params'], undefined);
+	t.is(config.rules['prefer-destructuring'], undefined);
+	t.is(config.rules['promise/prefer-await-to-then'], undefined);
+});
+
+test('buildConfig: engines: invalid range', t => {
+	const config = manager.buildConfig({engines: {node: '4'}});
+
+	// Do not include any Node.js version specific rules
+	t.is(config.rules['prefer-spread'], undefined);
+	t.is(config.rules['prefer-rest-params'], undefined);
+	t.is(config.rules['prefer-destructuring'], undefined);
+	t.is(config.rules['promise/prefer-await-to-then'], undefined);
+});
+
+test('buildConfig: engines: >=4', t => {
+	const config = manager.buildConfig({engines: {node: '>=4'}});
+
+	// Do not include rules for Node.js 5 and above
+	t.is(config.rules['unicorn/prefer-spread'], undefined);
+	// Do not include rules for Node.js 6 and above
+	t.is(config.rules['prefer-rest-params'], undefined);
+	t.is(config.rules['prefer-destructuring'], undefined);
+	// Do not include rules for Node.js 8 and above
+	t.is(config.rules['promise/prefer-await-to-then'], undefined);
+});
+
+test('buildConfig: engines: >=4.1', t => {
+	const config = manager.buildConfig({engines: {node: '>=5.1'}});
+
+	// Do not include rules for Node.js 5 and above
+	t.is(config.rules['unicorn/prefer-spread'], 'error');
+	// Do not include rules for Node.js 6 and above
+	t.is(config.rules['prefer-rest-params'], undefined);
+	t.is(config.rules['prefer-destructuring'], undefined);
+	// Do not include rules for Node.js 8 and above
+	t.is(config.rules['promise/prefer-await-to-then'], undefined);
+});
+
+test('buildConfig: engines: >=6', t => {
+	const config = manager.buildConfig({engines: {node: '>=6'}});
+
+	// Include rules for Node.js 5 and above
+	t.is(config.rules['unicorn/prefer-spread'], 'error');
+	// Include rules for Node.js 6 and above
+	t.is(config.rules['prefer-rest-params'], 'error');
+	t.deepEqual(config.rules['prefer-destructuring'], [
+		'error', {array: true, object: true}, {enforceForRenamedProperties: true}
+	]);
+	// Do not include rules for Node.js 8 and above
+	t.is(config.rules['promise/prefer-await-to-then'], undefined);
+});
+
+test('buildConfig: engines: >=8', t => {
+	const config = manager.buildConfig({engines: {node: '>=8'}});
+
+	// Include rules for Node.js 5 and above
+	t.is(config.rules['unicorn/prefer-spread'], 'error');
+	// Include rules for Node.js 6 and above
+	t.is(config.rules['prefer-rest-params'], 'error');
+	t.deepEqual(config.rules['prefer-destructuring'], [
+		'error', {array: true, object: true}, {enforceForRenamedProperties: true}
+	]);
+	// Include rules for Node.js 8 and above
+	t.is(config.rules['promise/prefer-await-to-then'], 'error');
+});
+
 test('mergeWithPrettierConf: use `singleQuote`, `trailingComma`, `bracketSpacing` and `jsxBracketSameLine` from `prettier` config if defined', t => {
 	const cwd = path.resolve('fixtures', 'prettier');
 	const result = manager.mergeWithPrettierConf({cwd});
@@ -255,26 +338,47 @@ test('groupConfigs', t => {
 test('mergeWithPkgConf: use child if closest', t => {
 	const cwd = path.resolve('fixtures', 'nested', 'child');
 	const result = manager.mergeWithPkgConf({cwd});
-	const expected = Object.assign({}, childConfig.xo, {cwd});
+	const expected = Object.assign({}, childConfig.xo, {cwd}, {engines: {}});
 	t.deepEqual(result, expected);
 });
 
 test('mergeWithPkgConf: use parent if closest', t => {
 	const cwd = path.resolve('fixtures', 'nested');
 	const result = manager.mergeWithPkgConf({cwd});
-	const expected = Object.assign({}, parentConfig.xo, {cwd});
+	const expected = Object.assign({}, parentConfig.xo, {cwd}, {engines: {}});
 	t.deepEqual(result, expected);
 });
 
 test('mergeWithPkgConf: use parent if child is ignored', t => {
 	const cwd = path.resolve('fixtures', 'nested', 'child-ignore');
 	const result = manager.mergeWithPkgConf({cwd});
-	const expected = Object.assign({}, parentConfig.xo, {cwd});
+	const expected = Object.assign({}, parentConfig.xo, {cwd}, {engines: {}});
 	t.deepEqual(result, expected);
 });
 
 test('mergeWithPkgConf: use child if child is empty', t => {
 	const cwd = path.resolve('fixtures', 'nested', 'child-empty');
 	const result = manager.mergeWithPkgConf({cwd});
-	t.deepEqual(result, {cwd});
+	t.deepEqual(result, {cwd, engines: {}});
+});
+
+test('mergeWithPkgConf: read engines from package.json', t => {
+	const cwd = path.resolve('fixtures', 'engines');
+	const result = manager.mergeWithPkgConf({cwd});
+	const expected = Object.assign({}, {engines: enginesConfig.engines}, {cwd});
+	t.deepEqual(result, expected);
+});
+
+test('mergeWithPkgConf: XO engine options supersede package.json\'s', t => {
+	const cwd = path.resolve('fixtures', 'engines');
+	const result = manager.mergeWithPkgConf({cwd, engines: {node: '>=8'}});
+	const expected = Object.assign({}, {engines: {node: '>=8'}}, {cwd});
+	t.deepEqual(result, expected);
+});
+
+test('mergeWithPkgConf: XO engine options false supersede package.json\'s', t => {
+	const cwd = path.resolve('fixtures', 'engines');
+	const result = manager.mergeWithPkgConf({cwd, engines: false});
+	const expected = Object.assign({}, {engines: false}, {cwd});
+	t.deepEqual(result, expected);
 });