1 | /**
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2 | * @fileoverview A rule to suggest using of the spread operator instead of `.apply()`.
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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 | const astUtils = require("../ast-utils");
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9 |
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10 | //------------------------------------------------------------------------------
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11 | // Helpers
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12 | //------------------------------------------------------------------------------
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13 |
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14 | /**
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15 | * Checks whether or not a node is a `.apply()` for variadic.
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16 | * @param {ASTNode} node - A CallExpression node to check.
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17 | * @returns {boolean} Whether or not the node is a `.apply()` for variadic.
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18 | */
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19 | function isVariadicApplyCalling(node) {
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20 | return (
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21 | node.callee.type === "MemberExpression" &&
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22 | node.callee.property.type === "Identifier" &&
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23 | node.callee.property.name === "apply" &&
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24 | node.callee.computed === false &&
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25 | node.arguments.length === 2 &&
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26 | node.arguments[1].type !== "ArrayExpression" &&
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27 | node.arguments[1].type !== "SpreadElement"
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28 | );
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29 | }
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30 |
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31 | /**
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32 | * Checks whether or not the tokens of two given nodes are same.
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33 | * @param {ASTNode} left - A node 1 to compare.
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34 | * @param {ASTNode} right - A node 2 to compare.
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35 | * @param {SourceCode} sourceCode - The ESLint source code object.
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36 | * @returns {boolean} the source code for the given node.
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37 | */
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38 | function equalTokens(left, right, sourceCode) {
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39 | const tokensL = sourceCode.getTokens(left);
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40 | const tokensR = sourceCode.getTokens(right);
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41 |
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42 | if (tokensL.length !== tokensR.length) {
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43 | return false;
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44 | }
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45 | for (let i = 0; i < tokensL.length; ++i) {
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46 | if (tokensL[i].type !== tokensR[i].type ||
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47 | tokensL[i].value !== tokensR[i].value
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48 | ) {
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49 | return false;
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50 | }
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51 | }
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52 |
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53 | return true;
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54 | }
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55 |
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56 | /**
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57 | * Checks whether or not `thisArg` is not changed by `.apply()`.
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58 | * @param {ASTNode|null} expectedThis - The node that is the owner of the applied function.
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59 | * @param {ASTNode} thisArg - The node that is given to the first argument of the `.apply()`.
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60 | * @param {RuleContext} context - The ESLint rule context object.
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61 | * @returns {boolean} Whether or not `thisArg` is not changed by `.apply()`.
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62 | */
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63 | function isValidThisArg(expectedThis, thisArg, context) {
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64 | if (!expectedThis) {
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65 | return astUtils.isNullOrUndefined(thisArg);
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66 | }
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67 | return equalTokens(expectedThis, thisArg, context);
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68 | }
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69 |
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70 | //------------------------------------------------------------------------------
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71 | // Rule Definition
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72 | //------------------------------------------------------------------------------
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73 |
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74 | module.exports = {
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75 | meta: {
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76 | docs: {
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77 | description: "require spread operators instead of `.apply()`",
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78 | category: "ECMAScript 6",
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79 | recommended: false
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80 | },
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81 |
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82 | schema: [],
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83 |
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84 | fixable: "code"
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85 | },
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86 |
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87 | create(context) {
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88 | const sourceCode = context.getSourceCode();
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89 |
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90 | return {
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91 | CallExpression(node) {
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92 | if (!isVariadicApplyCalling(node)) {
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93 | return;
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94 | }
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95 |
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96 | const applied = node.callee.object;
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97 | const expectedThis = (applied.type === "MemberExpression") ? applied.object : null;
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98 | const thisArg = node.arguments[0];
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99 |
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100 | if (isValidThisArg(expectedThis, thisArg, sourceCode)) {
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101 | context.report({
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102 | node,
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103 | message: "Use the spread operator instead of '.apply()'.",
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104 | fix(fixer) {
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105 | if (expectedThis && expectedThis.type !== "Identifier") {
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106 |
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107 | // Don't fix cases where the `this` value could be a computed expression.
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108 | return null;
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109 | }
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110 |
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111 | const propertyDot = sourceCode.getFirstTokenBetween(applied, node.callee.property, token => token.value === ".");
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112 |
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113 | return fixer.replaceTextRange([propertyDot.range[0], node.range[1]], `(...${sourceCode.getText(node.arguments[1])})`);
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114 | }
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115 | });
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116 | }
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117 | }
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118 | };
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119 | }
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120 | };
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