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Add prefer-import-meta-properties rule (#2607)
Co-authored-by: fisker <[email protected]> Co-authored-by: Sindre Sorhus <[email protected]>
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‎docs/rules/prefer-import-meta-properties.md

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# Prefer `import.meta.{dirname,filename}` over legacy techniques for getting file paths
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🚫 This rule is _disabled_ in the ✅ `recommended` [config](https://github.com/sindresorhus/eslint-plugin-unicorn#recommended-config).
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🔧 This rule is automatically fixable by the [`--fix` CLI option](https://eslint.org/docs/latest/user-guide/command-line-interface#--fix).
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<!-- end auto-generated rule header -->
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<!-- Do not manually modify this header. Run: `npm run fix:eslint-docs` -->
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Starting with Node.js 20.11, [`import.meta.dirname`](https://nodejs.org/api/esm.html#importmetadirname) and [`import.meta.filename`](https://nodejs.org/api/esm.html#importmetafilename) have been introduced in ES modules.
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> `import.meta.filename` is the same as the `url.fileURLToPath()` of the `import.meta.url`.\
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> `import.meta.dirname` is the same as the `path.dirname()` of the `import.meta.filename`.
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This rule replaces legacy patterns with `import.meta.{dirname,filename}`.
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## Examples
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```js
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import path from 'node:path';
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import {fileURLToPath} from "node:url";
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// ❌
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const filename = fileURLToPath(import.meta.url);
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// ✅
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const filename = import.meta.filename;
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```
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```js
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import path from 'node:path';
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import {fileURLToPath} from 'node:url';
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// ❌
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const dirname = path.dirname(fileURLToPath(import.meta.url));
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const dirname = path.dirname(import.meta.filename);
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const dirname = fileURLToPath(new URL('.', import.meta.url));
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// ✅
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const dirname = import.meta.dirname;
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```

‎eslint.dogfooding.config.js

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@@ -45,6 +45,7 @@ const config = [
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],
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rules: {
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'unicorn/prefer-module': 'off',
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'unicorn/prefer-import-meta-properties': 'off', // We can enable this rule when we drop support for Node.js v18.
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},
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},
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];

‎readme.md

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| [prefer-event-target](docs/rules/prefer-event-target.md) | Prefer `EventTarget` over `EventEmitter`. | ✅ | | |
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| [prefer-export-from](docs/rules/prefer-export-from.md) | Prefer `export…from` when re-exporting. | ✅ | 🔧 | 💡 |
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| [prefer-global-this](docs/rules/prefer-global-this.md) | Prefer `globalThis` over `window`, `self`, and `global`. | ✅ | 🔧 | |
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| [prefer-import-meta-properties](docs/rules/prefer-import-meta-properties.md) | Prefer `import.meta.{dirname,filename}` over legacy techniques for getting file paths. | | 🔧 | |
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| [prefer-includes](docs/rules/prefer-includes.md) | Prefer `.includes()` over `.indexOf()`, `.lastIndexOf()`, and `Array#some()` when checking for existence or non-existence. | ✅ | 🔧 | 💡 |
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| [prefer-json-parse-buffer](docs/rules/prefer-json-parse-buffer.md) | Prefer reading a JSON file as a buffer. | | 🔧 | |
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| [prefer-keyboard-event-key](docs/rules/prefer-keyboard-event-key.md) | Prefer `KeyboardEvent#key` over `KeyboardEvent#keyCode`. | ✅ | 🔧 | |

‎rules/index.js

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@@ -87,6 +87,7 @@ import preferDomNodeTextContent from './prefer-dom-node-text-content.js';
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import preferEventTarget from './prefer-event-target.js';
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import preferExportFrom from './prefer-export-from.js';
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import preferGlobalThis from './prefer-global-this.js';
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import preferImportMetaProperties from './prefer-import-meta-properties.js';
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import preferIncludes from './prefer-includes.js';
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import preferJsonParseBuffer from './prefer-json-parse-buffer.js';
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import preferKeyboardEventKey from './prefer-keyboard-event-key.js';
@@ -217,6 +218,7 @@ const rules = {
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'prefer-event-target': createRule(preferEventTarget, 'prefer-event-target'),
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'prefer-export-from': createRule(preferExportFrom, 'prefer-export-from'),
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'prefer-global-this': createRule(preferGlobalThis, 'prefer-global-this'),
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'prefer-import-meta-properties': createRule(preferImportMetaProperties, 'prefer-import-meta-properties'),
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'prefer-includes': createRule(preferIncludes, 'prefer-includes'),
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'prefer-json-parse-buffer': createRule(preferJsonParseBuffer, 'prefer-json-parse-buffer'),
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'prefer-keyboard-event-key': createRule(preferKeyboardEventKey, 'prefer-keyboard-event-key'),

‎rules/prefer-import-meta-properties.js

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import {findVariable} from '@eslint-community/eslint-utils';
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import {
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isMemberExpression,
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isCallExpression,
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isNewExpression,
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isMethodCall,
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} from './ast/index.js';
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const ERROR_DIRNAME = 'error/calculate-dirname';
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const ERROR_FILENAME = 'error/calculate-filename';
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const messages = {
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[ERROR_DIRNAME]: 'Do not construct dirname.',
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[ERROR_FILENAME]: 'Do not construct filename using `fileURLToPath()`.',
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};
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const isParentLiteral = node => {
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if (node?.type !== 'Literal') {
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return false;
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}
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return node.value === '.' || node.value === './';
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};
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const isImportMeta = node =>
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node.type === 'MetaProperty'
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&& node.meta.name === 'import'
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&& node.property.name === 'meta';
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function isNodeBuiltinModuleFunctionCall(node, {modules, functionName, sourceCode}) {
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if (!isCallExpression(node, {optional: false, argumentsLength: 1})) {
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return false;
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}
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const visited = new Set();
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return checkExpression(node.callee, 'property');
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/** @param {import('estree').Expression} node */
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function checkExpression(node, checkKind) {
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if (node.type === 'MemberExpression') {
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if (!(
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checkKind === 'property'
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&& isMemberExpression(node, {property: functionName, computed: false, optional: false})
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)) {
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return false;
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}
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return checkExpression(node.object, 'module');
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}
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if (node.type === 'CallExpression') {
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if (checkKind !== 'module') {
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return false;
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}
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// `process.getBuiltinModule('x')`
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return (
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isMethodCall(node, {
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object: 'process',
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method: 'getBuiltinModule',
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argumentsLength: 1,
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optionalMember: false,
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optionalCall: false,
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})
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&& isModuleLiteral(node.arguments[0])
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);
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}
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if (node.type !== 'Identifier') {
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return false;
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}
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if (visited.has(node)) {
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return false;
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}
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visited.add(node);
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const variable = findVariable(sourceCode.getScope(node), node);
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if (!variable || variable.defs.length !== 1) {
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return;
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}
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return checkDefinition(variable.defs[0], checkKind);
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}
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/** @param {import('eslint').Scope.Definition} define */
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function checkDefinition(define, checkKind) {
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if (define.type === 'ImportBinding') {
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if (!isModuleLiteral(define.parent.source)) {
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return false;
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}
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const specifier = define.node;
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return checkKind === 'module'
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? (specifier?.type === 'ImportDefaultSpecifier' || specifier?.type === 'ImportNamespaceSpecifier')
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: (specifier?.type === 'ImportSpecifier' && specifier.imported.name === functionName);
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}
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return define.type === 'Variable' && checkPattern(define.name, checkKind);
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}
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/** @param {import('estree').Identifier | import('estree').ObjectPattern} node */
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function checkPattern(node, checkKind) {
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/** @type {{parent?: import('estree').Node}} */
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const {parent} = node;
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if (parent.type === 'VariableDeclarator') {
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if (
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!parent.init
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|| parent.id !== node
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|| parent.parent.type !== 'VariableDeclaration'
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|| parent.parent.kind !== 'const'
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) {
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return false;
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}
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return checkExpression(parent.init, checkKind);
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}
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if (parent.type === 'Property') {
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if (!(
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checkKind === 'property'
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&& parent.value === node
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&& !parent.computed
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&& parent.key.type === 'Identifier'
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&& parent.key.name === functionName
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)) {
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return false;
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}
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// Check for ObjectPattern
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return checkPattern(parent.parent, 'module');
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}
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return false;
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}
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function isModuleLiteral(node) {
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return node?.type === 'Literal' && modules.has(node.value);
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}
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}
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/**
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@returns {node is import('estree').SimpleCallExpression}
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*/
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function isUrlFileURLToPathCall(node, sourceCode) {
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return isNodeBuiltinModuleFunctionCall(node, {
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modules: new Set(['url', 'node:url']),
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functionName: 'fileURLToPath',
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sourceCode,
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});
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}
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/**
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@returns {node is import('estree').SimpleCallExpression}
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*/
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function isPathDirnameCall(node, sourceCode) {
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return isNodeBuiltinModuleFunctionCall(node, {
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modules: new Set(['path', 'node:path']),
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functionName: 'dirname',
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sourceCode,
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});
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}
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function create(context) {
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const {sourceCode} = context;
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context.on('MetaProperty', function * (node) {
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if (!isImportMeta(node)) {
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return;
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}
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/** @type {import('estree').Node} */
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const memberExpression = node.parent;
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if (!isMemberExpression(memberExpression, {
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properties: ['url', 'filename'],
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computed: false,
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optional: false,
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})) {
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return;
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}
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const propertyName = memberExpression.property.name;
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if (propertyName === 'url') {
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// `url.fileURLToPath(import.meta.url)`
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if (
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isUrlFileURLToPathCall(memberExpression.parent, sourceCode)
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&& memberExpression.parent.arguments[0] === memberExpression
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) {
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yield * iterateProblemsFromFilename(memberExpression.parent, {
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reportFilenameNode: true,
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});
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return;
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}
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// `new URL(import.meta.url)`
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// `new URL('.', import.meta.url)`
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// `new URL('./', import.meta.url)`
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if (isNewExpression(memberExpression.parent, {name: 'URL', minimumArguments: 1, maximumArguments: 2})) {
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const newUrl = memberExpression.parent;
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const urlParent = newUrl.parent;
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// `new URL(import.meta.url)`
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if (
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newUrl.arguments.length === 1
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&& newUrl.arguments[0] === memberExpression
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// `url.fileURLToPath(new URL(import.meta.url))`
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&& isUrlFileURLToPathCall(urlParent, sourceCode)
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&& urlParent.arguments[0] === newUrl
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) {
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yield * iterateProblemsFromFilename(urlParent, {
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reportFilenameNode: true,
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});
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return;
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}
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// `url.fileURLToPath(new URL(".", import.meta.url))`
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// `url.fileURLToPath(new URL("./", import.meta.url))`
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if (
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newUrl.arguments.length === 2
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&& isParentLiteral(newUrl.arguments[0])
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&& newUrl.arguments[1] === memberExpression
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&& isUrlFileURLToPathCall(urlParent, sourceCode)
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&& urlParent.arguments[0] === newUrl
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) {
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yield getProblem(urlParent, 'dirname');
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}
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}
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return;
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}
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if (propertyName === 'filename') {
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yield * iterateProblemsFromFilename(memberExpression);
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}
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/**
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Iterates over reports where a given filename expression node
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would be used to convert it to a dirname.
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@param { import('estree').Expression} node
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*/
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function * iterateProblemsFromFilename(node, {reportFilenameNode = false} = {}) {
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/** @type {{parent: import('estree').Node}} */
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const {parent} = node;
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// `path.dirname(filename)`
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if (
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isPathDirnameCall(parent, sourceCode)
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&& parent.arguments[0] === node
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) {
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yield getProblem(parent, 'dirname');
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return;
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}
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if (reportFilenameNode) {
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yield getProblem(node, 'filename');
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}
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if (
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parent.type !== 'VariableDeclarator'
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|| parent.init !== node
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|| parent.id.type !== 'Identifier'
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|| parent.parent.type !== 'VariableDeclaration'
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|| parent.parent.kind !== 'const'
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) {
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return;
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}
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/** @type {import('eslint').Scope.Variable|null} */
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const variable = findVariable(sourceCode.getScope(parent.id), parent.id);
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if (!variable) {
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return;
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}
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for (const reference of variable.references) {
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if (!reference.isReadOnly()) {
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continue;
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}
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/** @type {{parent: import('estree').Node}} */
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const {parent} = reference.identifier;
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if (
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isPathDirnameCall(parent, sourceCode)
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&& parent.arguments[0] === reference.identifier
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) {
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// Report `path.dirname(identifier)`
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yield getProblem(parent, 'dirname');
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}
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}
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}
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/**
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@param { import('estree').Node} node
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@param {'dirname' | 'filename'} name
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*/
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function getProblem(node, name) {
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return {
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node,
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messageId: name === 'dirname' ? ERROR_DIRNAME : ERROR_FILENAME,
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fix: fixer => fixer.replaceText(node, `import.meta.${name}`),
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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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const config = {
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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: 'Prefer `import.meta.{dirname,filename}` over legacy techniques for getting file paths.',
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recommended: false,
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},
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fixable: 'code',
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messages,
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},
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};
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export default config;

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