| /** | |
| * @fileoverview Disallow shadowing of NaN, undefined, and Infinity (ES5 section 15.1.1) | |
| * @author Michael Ficarra | |
| */ | |
| "use strict"; | |
| /** | |
| * Determines if a variable safely shadows undefined. | |
| * This is the case when a variable named `undefined` is never assigned to a value (i.e. it always shares the same value | |
| * as the global). | |
| * @param {eslintScope.Variable} variable The variable to check | |
| * @returns {boolean} true if this variable safely shadows `undefined` | |
| */ | |
| function safelyShadowsUndefined(variable) { | |
| return variable.name === "undefined" && | |
| variable.references.every(ref => !ref.isWrite()) && | |
| variable.defs.every(def => def.node.type === "VariableDeclarator" && def.node.init === null); | |
| } | |
| //------------------------------------------------------------------------------ | |
| // Rule Definition | |
| //------------------------------------------------------------------------------ | |
| module.exports = { | |
| meta: { | |
| type: "suggestion", | |
| docs: { | |
| description: "disallow identifiers from shadowing restricted names", | |
| category: "Variables", | |
| recommended: true, | |
| url: "https://eslint.org/docs/rules/no-shadow-restricted-names" | |
| }, | |
| schema: [] | |
| }, | |
| create(context) { | |
| const RESTRICTED = new Set(["undefined", "NaN", "Infinity", "arguments", "eval"]); | |
| return { | |
| "VariableDeclaration, :function, CatchClause"(node) { | |
| for (const variable of context.getDeclaredVariables(node)) { | |
| if (variable.defs.length > 0 && RESTRICTED.has(variable.name) && !safelyShadowsUndefined(variable)) { | |
| context.report({ | |
| node: variable.defs[0].name, | |
| message: "Shadowing of global property '{{idName}}'.", | |
| data: { | |
| idName: variable.name | |
| } | |
| }); | |
| } | |
| } | |
| } | |
| }; | |
| } | |
| }; |