1 | /**
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2 | * @fileoverview Rule to
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3 | * @author Toru Nagashima
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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 | //------------------------------------------------------------------------------
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9 | // Helpers
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10 | //------------------------------------------------------------------------------
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11 |
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12 | /**
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13 | * Gets the variable object of `arguments` which is defined implicitly.
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14 | * @param {eslint-scope.Scope} scope - A scope to get.
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15 | * @returns {eslint-scope.Variable} The found variable object.
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16 | */
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17 | function getVariableOfArguments(scope) {
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18 | const variables = scope.variables;
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19 |
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20 | for (let i = 0; i < variables.length; ++i) {
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21 | const variable = variables[i];
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22 |
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23 | if (variable.name === "arguments") {
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24 |
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25 | /*
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26 | * If there was a parameter which is named "arguments", the implicit "arguments" is not defined.
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27 | * So does fast return with null.
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28 | */
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29 | return (variable.identifiers.length === 0) ? variable : null;
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30 | }
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31 | }
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32 |
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33 | /* istanbul ignore next : unreachable */
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34 | return null;
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35 | }
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36 |
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37 | /**
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38 | * Checks if the given reference is not normal member access.
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39 | *
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40 | * - arguments .... true // not member access
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41 | * - arguments[i] .... true // computed member access
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42 | * - arguments[0] .... true // computed member access
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43 | * - arguments.length .... false // normal member access
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44 | *
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45 | * @param {eslint-scope.Reference} reference - The reference to check.
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46 | * @returns {boolean} `true` if the reference is not normal member access.
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47 | */
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48 | function isNotNormalMemberAccess(reference) {
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49 | const id = reference.identifier;
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50 | const parent = id.parent;
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51 |
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52 | return !(
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53 | parent.type === "MemberExpression" &&
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54 | parent.object === id &&
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55 | !parent.computed
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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 | // Rule Definition
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61 | //------------------------------------------------------------------------------
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62 |
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63 | module.exports = {
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64 | meta: {
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65 | docs: {
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66 | description: "require rest parameters instead of `arguments`",
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67 | category: "ECMAScript 6",
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68 | recommended: false,
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69 | url: "https://eslint.org/docs/rules/prefer-rest-params"
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70 | },
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71 |
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72 | schema: []
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73 | },
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74 |
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75 | create(context) {
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76 |
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77 | /**
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78 | * Reports a given reference.
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79 | *
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80 | * @param {eslint-scope.Reference} reference - A reference to report.
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81 | * @returns {void}
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82 | */
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83 | function report(reference) {
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84 | context.report({
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85 | node: reference.identifier,
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86 | loc: reference.identifier.loc,
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87 | message: "Use the rest parameters instead of 'arguments'."
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88 | });
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89 | }
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90 |
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91 | /**
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92 | * Reports references of the implicit `arguments` variable if exist.
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93 | *
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94 | * @returns {void}
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95 | */
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96 | function checkForArguments() {
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97 | const argumentsVar = getVariableOfArguments(context.getScope());
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98 |
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99 | if (argumentsVar) {
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100 | argumentsVar
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101 | .references
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102 | .filter(isNotNormalMemberAccess)
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103 | .forEach(report);
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104 | }
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105 | }
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106 |
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107 | return {
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108 | "FunctionDeclaration:exit": checkForArguments,
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109 | "FunctionExpression:exit": checkForArguments
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110 | };
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111 | }
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112 | };
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