1 | /**
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2 | * @fileoverview Disallow shadowing of NaN, undefined, and Infinity (ES5 section 15.1.1)
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3 | * @author Michael Ficarra
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4 | */
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5 | ;
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6 |
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7 | /**
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8 | * Determines if a variable safely shadows undefined.
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9 | * This is the case when a variable named `undefined` is never assigned to a value (i.e. it always shares the same value
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10 | * as the global).
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11 | * @param {eslintScope.Variable} variable The variable to check
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12 | * @returns {boolean} true if this variable safely shadows `undefined`
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13 | */
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14 | function safelyShadowsUndefined(variable) {
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15 | return variable.name === "undefined" &&
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16 | variable.references.every(ref => !ref.isWrite()) &&
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17 | variable.defs.every(def => def.node.type === "VariableDeclarator" && def.node.init === null);
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18 | }
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19 |
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20 | //------------------------------------------------------------------------------
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21 | // Rule Definition
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22 | //------------------------------------------------------------------------------
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23 |
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24 | module.exports = {
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25 | meta: {
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26 | type: "suggestion",
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27 |
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28 | docs: {
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29 | description: "disallow identifiers from shadowing restricted names",
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30 | category: "Variables",
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31 | recommended: true,
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32 | url: "https://eslint.org/docs/rules/no-shadow-restricted-names"
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33 | },
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34 |
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35 | schema: []
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36 | },
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37 |
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38 | create(context) {
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39 |
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40 |
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41 | const RESTRICTED = new Set(["undefined", "NaN", "Infinity", "arguments", "eval"]);
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42 |
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43 | return {
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44 | "VariableDeclaration, :function, CatchClause"(node) {
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45 | for (const variable of context.getDeclaredVariables(node)) {
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46 | if (variable.defs.length > 0 && RESTRICTED.has(variable.name) && !safelyShadowsUndefined(variable)) {
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47 | context.report({
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48 | node: variable.defs[0].name,
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49 | message: "Shadowing of global property '{{idName}}'.",
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50 | data: {
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51 | idName: variable.name
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52 | }
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53 | });
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54 | }
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55 | }
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56 | }
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57 | };
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58 |
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59 | }
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60 | };
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