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Mesteerysindresorhus
Mesteery
and
sindresorhus
authoredNov 2, 2023
Add no-unnecessary-polyfills rule (#1717)
Co-authored-by: Sindre Sorhus <sindresorhus@gmail.com>
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v59.0.0v50.0.0
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‎configs/recommended.js

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

‎docs/rules/no-unnecessary-polyfills.md

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# Enforce the use of built-in methods instead of unnecessary polyfills
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💼 This rule is enabled in the ✅ `recommended` [config](https://github.com/sindresorhus/eslint-plugin-unicorn#preset-configs).
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<!-- end auto-generated rule header -->
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<!-- Do not manually modify RULE_NOTICE part. Run: `npm run generate-rule-notices` -->
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<!-- RULE_NOTICE -->
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✅ _This rule is part of the [recommended](https://github.com/sindresorhus/eslint-plugin-unicorn#recommended-config) config._
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<!-- /RULE_NOTICE -->
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This rules helps to use existing methods instead of using extra polyfills.
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## Fail
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package.json
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```json
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{
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"engines": {
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"node": ">=8"
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}
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}
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```
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```js
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const assign = require('object-assign');
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```
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## Pass
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package.json
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```json
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{
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"engines": {
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"node": "4"
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}
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}
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```
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```js
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const assign = require('object-assign'); // Passes as Object.assign is not supported
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```
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## Options
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Type: `object`
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### targets
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Type: `string | string[] | object`
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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.
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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.
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```js
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"unicorn/no-unnecessary-polyfills": [
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"error",
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{
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"targets": "node >=12"
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}
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]
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```
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```js
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"unicorn/no-unnecessary-polyfills": [
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"error",
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{
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"targets": [
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"node 14.1.0",
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"chrome 95"
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]
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}
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]
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```
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```js
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"unicorn/no-unnecessary-polyfills": [
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"error",
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{
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"targets": {
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"node": "current",
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"firefox": "15"
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}
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}
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]
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```

‎package.json

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

‎readme.md

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| [no-this-assignment](docs/rules/no-this-assignment.md) | Disallow assigning `this` to a variable. | ✅ | | |
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| [no-typeof-undefined](docs/rules/no-typeof-undefined.md) | Disallow comparing `undefined` using `typeof`. | ✅ | 🔧 | 💡 |
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| [no-unnecessary-await](docs/rules/no-unnecessary-await.md) | Disallow awaiting non-promise values. | ✅ | 🔧 | |
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| [no-unnecessary-polyfills](docs/rules/no-unnecessary-polyfills.md) | Enforce the use of built-in methods instead of unnecessary polyfills. | ✅ | | |
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| [no-unreadable-array-destructuring](docs/rules/no-unreadable-array-destructuring.md) | Disallow unreadable array destructuring. | ✅ | 🔧 | |
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| [no-unreadable-iife](docs/rules/no-unreadable-iife.md) | Disallow unreadable IIFEs. | ✅ | | |
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| [no-unused-properties](docs/rules/no-unused-properties.md) | Disallow unused object properties. | | | |

‎rules/no-unnecessary-polyfills.js

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

‎test/no-unnecessary-polyfills.mjs

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import {getTester} from './utils/test.mjs';
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const {test} = getTester(import.meta);
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test({
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valid: [
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{
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code: 'require("object-assign")',
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options: [{targets: {node: '0.1.0'}}],
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},
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{
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code: 'require("this-is-not-a-polyfill")',
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options: [{targets: {node: '0.1.0'}}],
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},
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{
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code: 'import assign from "object-assign"',
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options: [{targets: {node: '0.1.0'}}],
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},
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{
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code: 'import("object-assign")',
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options: [{targets: {node: '0.1.0'}}],
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},
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{
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code: 'require("object-assign")',
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options: [{targets: 'node <4'}],
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},
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{
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code: 'require("object-assign")',
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options: [{targets: 'node >3'}],
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},
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{
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code: 'require()',
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options: [{targets: 'node >3'}],
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},
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{
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code: 'import("")',
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options: [{targets: 'node >3'}],
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},
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{
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code: 'import(null)',
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options: [{targets: 'node >3'}],
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},
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{
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code: 'require(null)',
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options: [{targets: 'node >3'}],
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},
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{
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code: 'require("" )',
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options: [{targets: 'node >3'}],
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},
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],
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invalid: [
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{
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code: 'require("setprototypeof")',
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options: [{targets: 'node >4'}],
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errors: [{message: 'Use built-in instead.'}],
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},
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{
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code: 'require("core-js/features/array/last-index-of")',
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options: [{targets: 'node >6.5'}],
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errors: [{message: 'Use built-in instead.'}],
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},
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{
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code: 'require("core-js-pure/features/array/from")',
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options: [{targets: 'node >7'}],
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errors: [{message: 'All polyfilled features imported from `core-js-pure/features/array/from` are available as built-ins. Use the built-ins instead.'}],
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},
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{
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code: 'require("core-js/features/array/from")',
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options: [{targets: 'node >7'}],
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errors: [{message: 'All polyfilled features imported from `core-js/features/array/from` are available as built-ins. Use the built-ins instead.'}],
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},
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{
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code: 'require("core-js/features/typed-array")',
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options: [{targets: 'node >16'}],
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errors: [{message: 'All polyfilled features imported from `core-js/features/typed-array` are available as built-ins. Use the built-ins instead.'}],
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},
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{
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code: 'require("es6-symbol")',
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options: [{targets: 'node >15'}],
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errors: [{message: 'Use built-in instead.'}],
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},
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{
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code: 'require("code-point-at")',
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options: [{targets: 'node >4'}],
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errors: [{message: 'Use built-in instead.'}],
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},
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{
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code: 'require("object.getownpropertydescriptors")',
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options: [{targets: 'node >8'}],
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errors: [{message: 'Use built-in instead.'}],
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},
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{
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code: 'require("string.prototype.padstart")',
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options: [{targets: 'node >8'}],
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errors: [{message: 'Use built-in instead.'}],
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},
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{
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code: 'require("p-finally")',
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options: [{targets: 'node >10.4'}],
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errors: [{message: 'Use built-in instead.'}],
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},
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{
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code: 'require("promise-polyfill")',
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options: [{targets: 'node >15'}],
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errors: [{message: 'Use built-in instead.'}],
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},
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{
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code: 'require("es6-promise")',
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options: [{targets: 'node >15'}],
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errors: [{message: 'Use built-in instead.'}],
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},
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{
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code: 'require("object-assign")',
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options: [{targets: 'node 6'}],
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errors: [{message: 'Use built-in instead.'}],
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},
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{
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code: 'import assign from "object-assign"',
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options: [{targets: 'node 6'}],
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errors: [{message: 'Use built-in instead.'}],
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},
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{
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code: 'import("object-assign")',
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options: [{targets: 'node 6'}],
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errors: [{message: 'Use built-in instead.'}],
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},
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{
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code: 'require("object-assign")',
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options: [{targets: 'node >6'}],
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errors: [{message: 'Use built-in instead.'}],
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},
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{
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code: 'require("object-assign")',
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options: [{targets: 'node 8'}],
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errors: [{message: 'Use built-in instead.'}],
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},
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{
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code: 'require("array-from")',
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options: [{targets: 'node >7'}],
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errors: [{message: 'Use built-in instead.'}],
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},
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{
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code: 'require("array-find-index")',
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options: [{targets: 'node >4.0.0'}],
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errors: [{message: 'Use built-in instead.'}],
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},
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{
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code: 'require("array-find-index")',
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options: [{targets: 'node >4'}],
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errors: [{message: 'Use built-in instead.'}],
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},
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{
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code: 'require("array-find-index")',
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options: [{targets: 'node 4'}],
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errors: [{message: 'Use built-in instead.'}],
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},
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{
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code: 'require("mdn-polyfills/Array.prototype.findIndex")',
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options: [{targets: 'node 4'}],
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errors: [{message: 'Use built-in instead.'}],
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},
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{
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code: 'require("weakmap-polyfill")',
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options: [{targets: 'node 12'}],
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errors: [{message: 'Use built-in instead.'}],
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},
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{
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code: 'require("typed-array-float64-array-polyfill")',
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options: [{targets: 'node 17'}],
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errors: [{message: 'Use built-in instead.'}],
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},
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],
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});

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