Add no-unnecessary-polyfills rule (#1717)

Co-authored-by: Sindre Sorhus <[email protected]>

configs/recommended.js

@@ -54,6 +54,7 @@ module.exports = {
 		'unicorn/no-this-assignment': 'error',
 		'unicorn/no-typeof-undefined': 'error',
 		'unicorn/no-unnecessary-await': 'error',
+		'unicorn/no-unnecessary-polyfills': 'error',
 		'unicorn/no-unreadable-array-destructuring': 'error',
 		'unicorn/no-unreadable-iife': 'error',
 		'unicorn/no-unused-properties': 'off',

docs/rules/no-unnecessary-polyfills.md

@@ -0,0 +1,91 @@
+# Enforce the use of built-in methods instead of unnecessary polyfills
+
+💼 This rule is enabled in the ✅ `recommended` [config](https://github.com/sindresorhus/eslint-plugin-unicorn#preset-configs).
+
+<!-- end auto-generated rule header -->
+
+<!-- Do not manually modify RULE_NOTICE part. Run: `npm run generate-rule-notices` -->
+<!-- RULE_NOTICE -->
+
+✅ _This rule is part of the [recommended](https://github.com/sindresorhus/eslint-plugin-unicorn#recommended-config) config._
+
+<!-- /RULE_NOTICE -->
+
+This rules helps to use existing methods instead of using extra polyfills.
+
+## Fail
+
+package.json
+
+```json
+{
+	"engines": {
+		"node": ">=8"
+	}
+}
+```
+
+```js
+const assign = require('object-assign');
+```
+
+## Pass
+
+package.json
+
+```json
+{
+	"engines": {
+		"node": "4"
+	}
+}
+```
+
+```js
+const assign = require('object-assign'); // Passes as Object.assign is not supported
+```
+
+## Options
+
+Type: `object`
+
+### targets
+
+Type: `string | string[] | object`
+
+Specify the target versions, which could be a Browserlist query or a targets object. See the [core-js-compat `targets` option](https://github.com/zloirock/core-js/tree/HEAD/packages/core-js-compat#targets-option) for more info.
+
+If the option is not specified, the target versions are defined using the [`browserlist`](https://browsersl.ist) field in package.json, or as a last resort, the `engines` field in package.json.
+
+```js
+"unicorn/no-unnecessary-polyfills": [
+	"error",
+	{
+		"targets": "node >=12"
+	}
+]
+```
+
+```js
+"unicorn/no-unnecessary-polyfills": [
+	"error",
+	{
+		"targets": [
+			"node 14.1.0",
+			"chrome 95"
+		]
+	}
+]
+```
+
+```js
+"unicorn/no-unnecessary-polyfills": [
+	"error",
+	{
+		"targets": {
+			"node": "current",
+			"firefox": "15"
+		}
+	}
+]
+```

package.json

@@ -51,6 +51,7 @@
 		"@eslint-community/eslint-utils": "^4.4.0",
 		"ci-info": "^3.8.0",
 		"clean-regexp": "^1.0.0",
+		"core-js-compat": "^3.33.2",
 		"esquery": "^1.5.0",
 		"indent-string": "^4.0.0",
 		"is-builtin-module": "^3.2.1",

readme.md

@@ -96,6 +96,7 @@ If you don't use the preset, ensure you use the same `env` and `parserOptions` c
 | [no-this-assignment](docs/rules/no-this-assignment.md)                                           | Disallow assigning `this` to a variable.                                                                                                                                                                          | ✅  |    |    |
 | [no-typeof-undefined](docs/rules/no-typeof-undefined.md)                                         | Disallow comparing `undefined` using `typeof`.                                                                                                                                                                    | ✅  | 🔧 | 💡 |
 | [no-unnecessary-await](docs/rules/no-unnecessary-await.md)                                       | Disallow awaiting non-promise values.                                                                                                                                                                             | ✅  | 🔧 |    |
+| [no-unnecessary-polyfills](docs/rules/no-unnecessary-polyfills.md)                               | Enforce the use of built-in methods instead of unnecessary polyfills.                                                                                                                                             | ✅  |    |    |
 | [no-unreadable-array-destructuring](docs/rules/no-unreadable-array-destructuring.md)             | Disallow unreadable array destructuring.                                                                                                                                                                          | ✅  | 🔧 |    |
 | [no-unreadable-iife](docs/rules/no-unreadable-iife.md)                                           | Disallow unreadable IIFEs.                                                                                                                                                                                        | ✅  |    |    |
 | [no-unused-properties](docs/rules/no-unused-properties.md)                                       | Disallow unused object properties.                                                                                                                                                                                |    |    |    |

rules/no-unnecessary-polyfills.js

@@ -0,0 +1,176 @@
+'use strict';
+const path = require('node:path');
+const readPkgUp = require('read-pkg-up');
+const coreJsCompat = require('core-js-compat');
+const {camelCase} = require('lodash');
+const isStaticRequire = require('./ast/is-static-require.js');
+
+const {data: compatData, entries: coreJsEntries} = coreJsCompat;
+
+const MESSAGE_ID_POLYFILL = 'unnecessaryPolyfill';
+const MESSAGE_ID_CORE_JS = 'unnecessaryCoreJsModule';
+const messages = {
+	[MESSAGE_ID_POLYFILL]: 'Use built-in instead.',
+	[MESSAGE_ID_CORE_JS]:
+		'All polyfilled features imported from `{{coreJsModule}}` are available as built-ins. Use the built-ins instead.',
+};
+
+const additionalPolyfillPatterns = {
+	'es.promise.finally': '|(p-finally)',
+	'es.object.set-prototype-of': '|(setprototypeof)',
+	'es.string.code-point-at': '|(code-point-at)',
+};
+
+const prefixes = '(mdn-polyfills/|polyfill-)';
+const suffixes = '(-polyfill)';
+const delimiter = '(\\.|-|\\.prototype\\.|/)?';
+
+const polyfills = Object.keys(compatData).map(feature => {
+	let [ecmaVersion, constructorName, methodName = ''] = feature.split('.');
+
+	if (ecmaVersion === 'es') {
+		ecmaVersion = '(es\\d*)';
+	}
+
+	constructorName = `(${constructorName}|${camelCase(constructorName)})`;
+	methodName &&= `(${methodName}|${camelCase(methodName)})`;
+
+	const methodOrConstructor = methodName || constructorName;
+
+	const patterns = [
+		`^((${prefixes}?(`,
+		methodName && `(${ecmaVersion}${delimiter}${constructorName}${delimiter}${methodName})|`, // Ex: es6-array-copy-within
+		methodName && `(${constructorName}${delimiter}${methodName})|`, // Ex: array-copy-within
+		`(${ecmaVersion}${delimiter}${constructorName}))`, // Ex: es6-array
+		`${suffixes}?)|`,
+		`(${prefixes}${methodOrConstructor}|${methodOrConstructor}${suffixes})`, // Ex: polyfill-copy-within / polyfill-promise
+		`${additionalPolyfillPatterns[feature] || ''})$`,
+	];
+
+	return {
+		feature,
+		pattern: new RegExp(patterns.join(''), 'i'),
+	};
+});
+
+function getTargets(options, dirname) {
+	if (options?.targets) {
+		return options.targets;
+	}
+
+	/** @type {readPkgUp.ReadResult | undefined} */
+	let packageResult;
+	try {
+		// It can fail if, for example, the package.json file has comments.
+		packageResult = readPkgUp.sync({normalize: false, cwd: dirname});
+	} catch {}
+
+	if (!packageResult) {
+		return;
+	}
+
+	const {browserlist, engines} = packageResult.packageJson;
+	return browserlist ?? engines;
+}
+
+function create(context) {
+	const targets = getTargets(context.options[0], path.dirname(context.filename));
+	if (!targets) {
+		return {};
+	}
+
+	let unavailableFeatures;
+	try {
+		unavailableFeatures = coreJsCompat({targets}).list;
+	} catch {
+		// This can happen if the targets are invalid or use unsupported syntax like `{node:'*'}`.
+		return {};
+	}
+
+	const checkFeatures = features => !features.every(feature => unavailableFeatures.includes(feature));
+
+	return {
+		Literal(node) {
+			if (
+				!(
+					(['ImportDeclaration', 'ImportExpression'].includes(node.parent.type) && node.parent.source === node)
+					|| (isStaticRequire(node.parent) && node.parent.arguments[0] === node)
+				)
+			) {
+				return;
+			}
+
+			const importedModule = node.value;
+			if (typeof importedModule !== 'string' || ['.', '/'].includes(importedModule[0])) {
+				return;
+			}
+
+			const coreJsModuleFeatures = coreJsEntries[importedModule.replace('core-js-pure', 'core-js')];
+
+			if (coreJsModuleFeatures) {
+				if (coreJsModuleFeatures.length > 1) {
+					if (checkFeatures(coreJsModuleFeatures)) {
+						return {
+							node,
+							messageId: MESSAGE_ID_CORE_JS,
+							data: {
+								coreJsModule: importedModule,
+							},
+						};
+					}
+				} else if (!unavailableFeatures.includes(coreJsModuleFeatures[0])) {
+					return {node, messageId: MESSAGE_ID_POLYFILL};
+				}
+
+				return;
+			}
+
+			const polyfill = polyfills.find(({pattern}) => pattern.test(importedModule));
+			if (polyfill) {
+				const [, namespace, method = ''] = polyfill.feature.split('.');
+				const [, features] = Object.entries(coreJsEntries).find(
+					entry => entry[0] === `core-js/full/${namespace}${method && '/'}${method}`,
+				);
+				if (checkFeatures(features)) {
+					return {node, messageId: MESSAGE_ID_POLYFILL};
+				}
+			}
+		},
+	};
+}
+
+const schema = [
+	{
+		type: 'object',
+		additionalProperties: false,
+		required: ['targets'],
+		properties: {
+			targets: {
+				oneOf: [
+					{
+						type: 'string',
+					},
+					{
+						type: 'array',
+					},
+					{
+						type: 'object',
+					},
+				],
+			},
+		},
+	},
+];
+
+/** @type {import('eslint').Rule.RuleModule} */
+module.exports = {
+	create,
+	meta: {
+		type: 'suggestion',
+		docs: {
+			description: 'Enforce the use of built-in methods instead of unnecessary polyfills.',
+		},
+		schema,
+		messages,
+	},
+};