| 1 | /**
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| 2 | * @fileoverview A rule to disallow the type conversions with shorter notations.
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| 3 | * @author Toru Nagashima
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| 4 | */
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| 5 |
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| 6 | "use strict";
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| 7 |
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| 8 | const astUtils = require("./utils/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 | const INDEX_OF_PATTERN = /^(?:i|lastI)ndexOf$/u;
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| 15 | const ALLOWABLE_OPERATORS = ["~", "!!", "+", "*"];
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| 16 |
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| 17 | /**
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| 18 | * Parses and normalizes an option object.
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| 19 | * @param {Object} options An option object to parse.
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| 20 | * @returns {Object} The parsed and normalized option object.
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| 21 | */
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| 22 | function parseOptions(options) {
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| 23 | return {
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| 24 | boolean: "boolean" in options ? options.boolean : true,
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| 25 | number: "number" in options ? options.number : true,
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| 26 | string: "string" in options ? options.string : true,
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| 27 | disallowTemplateShorthand: "disallowTemplateShorthand" in options ? options.disallowTemplateShorthand : false,
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| 28 | allow: options.allow || []
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| 29 | };
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| 30 | }
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| 31 |
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| 32 | /**
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| 33 | * Checks whether or not a node is a double logical negating.
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| 34 | * @param {ASTNode} node An UnaryExpression node to check.
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| 35 | * @returns {boolean} Whether or not the node is a double logical negating.
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| 36 | */
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| 37 | function isDoubleLogicalNegating(node) {
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| 38 | return (
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| 39 | node.operator === "!" &&
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| 40 | node.argument.type === "UnaryExpression" &&
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| 41 | node.argument.operator === "!"
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| 42 | );
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| 43 | }
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| 44 |
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| 45 | /**
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| 46 | * Checks whether or not a node is a binary negating of `.indexOf()` method calling.
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| 47 | * @param {ASTNode} node An UnaryExpression node to check.
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| 48 | * @returns {boolean} Whether or not the node is a binary negating of `.indexOf()` method calling.
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| 49 | */
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| 50 | function isBinaryNegatingOfIndexOf(node) {
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| 51 | if (node.operator !== "~") {
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| 52 | return false;
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| 53 | }
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| 54 | const callNode = astUtils.skipChainExpression(node.argument);
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| 55 |
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| 56 | return (
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| 57 | callNode.type === "CallExpression" &&
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| 58 | astUtils.isSpecificMemberAccess(callNode.callee, null, INDEX_OF_PATTERN)
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| 59 | );
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| 60 | }
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| 61 |
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| 62 | /**
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| 63 | * Checks whether or not a node is a multiplying by one.
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| 64 | * @param {BinaryExpression} node A BinaryExpression node to check.
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| 65 | * @returns {boolean} Whether or not the node is a multiplying by one.
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| 66 | */
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| 67 | function isMultiplyByOne(node) {
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| 68 | return node.operator === "*" && (
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| 69 | node.left.type === "Literal" && node.left.value === 1 ||
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| 70 | node.right.type === "Literal" && node.right.value === 1
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| 71 | );
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| 72 | }
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| 73 |
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| 74 | /**
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| 75 | * Checks whether the given node logically represents multiplication by a fraction of `1`.
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| 76 | * For example, `a * 1` in `a * 1 / b` is technically multiplication by `1`, but the
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| 77 | * whole expression can be logically interpreted as `a * (1 / b)` rather than `(a * 1) / b`.
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| 78 | * @param {BinaryExpression} node A BinaryExpression node to check.
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| 79 | * @param {SourceCode} sourceCode The source code object.
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| 80 | * @returns {boolean} Whether or not the node is a multiplying by a fraction of `1`.
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| 81 | */
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| 82 | function isMultiplyByFractionOfOne(node, sourceCode) {
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| 83 | return node.type === "BinaryExpression" &&
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| 84 | node.operator === "*" &&
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| 85 | (node.right.type === "Literal" && node.right.value === 1) &&
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| 86 | node.parent.type === "BinaryExpression" &&
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| 87 | node.parent.operator === "/" &&
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| 88 | node.parent.left === node &&
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| 89 | !astUtils.isParenthesised(sourceCode, node);
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| 90 | }
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| 91 |
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| 92 | /**
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| 93 | * Checks whether the result of a node is numeric or not
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| 94 | * @param {ASTNode} node The node to test
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| 95 | * @returns {boolean} true if the node is a number literal or a `Number()`, `parseInt` or `parseFloat` call
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| 96 | */
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| 97 | function isNumeric(node) {
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| 98 | return (
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| 99 | node.type === "Literal" && typeof node.value === "number" ||
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| 100 | node.type === "CallExpression" && (
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| 101 | node.callee.name === "Number" ||
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| 102 | node.callee.name === "parseInt" ||
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| 103 | node.callee.name === "parseFloat"
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| 104 | )
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| 105 | );
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| 106 | }
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| 107 |
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| 108 | /**
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| 109 | * Returns the first non-numeric operand in a BinaryExpression. Designed to be
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| 110 | * used from bottom to up since it walks up the BinaryExpression trees using
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| 111 | * node.parent to find the result.
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| 112 | * @param {BinaryExpression} node The BinaryExpression node to be walked up on
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| 113 | * @returns {ASTNode|null} The first non-numeric item in the BinaryExpression tree or null
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| 114 | */
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| 115 | function getNonNumericOperand(node) {
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| 116 | const left = node.left,
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| 117 | right = node.right;
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| 118 |
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| 119 | if (right.type !== "BinaryExpression" && !isNumeric(right)) {
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| 120 | return right;
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| 121 | }
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| 122 |
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| 123 | if (left.type !== "BinaryExpression" && !isNumeric(left)) {
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| 124 | return left;
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| 125 | }
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| 126 |
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| 127 | return null;
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| 128 | }
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| 129 |
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| 130 | /**
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| 131 | * Checks whether an expression evaluates to a string.
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| 132 | * @param {ASTNode} node node that represents the expression to check.
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| 133 | * @returns {boolean} Whether or not the expression evaluates to a string.
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| 134 | */
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| 135 | function isStringType(node) {
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| 136 | return astUtils.isStringLiteral(node) ||
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| 137 | (
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| 138 | node.type === "CallExpression" &&
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| 139 | node.callee.type === "Identifier" &&
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| 140 | node.callee.name === "String"
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| 141 | );
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| 142 | }
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| 143 |
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| 144 | /**
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| 145 | * Checks whether a node is an empty string literal or not.
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| 146 | * @param {ASTNode} node The node to check.
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| 147 | * @returns {boolean} Whether or not the passed in node is an
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| 148 | * empty string literal or not.
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| 149 | */
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| 150 | function isEmptyString(node) {
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| 151 | return astUtils.isStringLiteral(node) && (node.value === "" || (node.type === "TemplateLiteral" && node.quasis.length === 1 && node.quasis[0].value.cooked === ""));
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| 152 | }
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| 153 |
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| 154 | /**
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| 155 | * Checks whether or not a node is a concatenating with an empty string.
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| 156 | * @param {ASTNode} node A BinaryExpression node to check.
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| 157 | * @returns {boolean} Whether or not the node is a concatenating with an empty string.
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| 158 | */
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| 159 | function isConcatWithEmptyString(node) {
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| 160 | return node.operator === "+" && (
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| 161 | (isEmptyString(node.left) && !isStringType(node.right)) ||
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| 162 | (isEmptyString(node.right) && !isStringType(node.left))
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| 163 | );
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| 164 | }
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| 165 |
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| 166 | /**
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| 167 | * Checks whether or not a node is appended with an empty string.
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| 168 | * @param {ASTNode} node An AssignmentExpression node to check.
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| 169 | * @returns {boolean} Whether or not the node is appended with an empty string.
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| 170 | */
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| 171 | function isAppendEmptyString(node) {
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| 172 | return node.operator === "+=" && isEmptyString(node.right);
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| 173 | }
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| 174 |
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| 175 | /**
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| 176 | * Returns the operand that is not an empty string from a flagged BinaryExpression.
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| 177 | * @param {ASTNode} node The flagged BinaryExpression node to check.
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| 178 | * @returns {ASTNode} The operand that is not an empty string from a flagged BinaryExpression.
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| 179 | */
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| 180 | function getNonEmptyOperand(node) {
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| 181 | return isEmptyString(node.left) ? node.right : node.left;
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| 182 | }
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| 183 |
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| 184 | //------------------------------------------------------------------------------
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| 185 | // Rule Definition
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| 186 | //------------------------------------------------------------------------------
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| 187 |
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| 188 | /** @type {import('../shared/types').Rule} */
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| 189 | module.exports = {
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| 190 | meta: {
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| 191 | type: "suggestion",
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| 192 |
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| 193 | docs: {
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| 194 | description: "Disallow shorthand type conversions",
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| 195 | recommended: false,
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| 196 | url: "https://eslint.org/docs/latest/rules/no-implicit-coercion"
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| 197 | },
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| 198 |
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| 199 | fixable: "code",
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| 200 |
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| 201 | schema: [{
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| 202 | type: "object",
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| 203 | properties: {
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| 204 | boolean: {
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| 205 | type: "boolean",
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| 206 | default: true
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| 207 | },
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| 208 | number: {
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| 209 | type: "boolean",
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| 210 | default: true
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| 211 | },
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| 212 | string: {
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| 213 | type: "boolean",
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| 214 | default: true
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| 215 | },
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| 216 | disallowTemplateShorthand: {
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| 217 | type: "boolean",
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| 218 | default: false
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| 219 | },
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| 220 | allow: {
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| 221 | type: "array",
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| 222 | items: {
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| 223 | enum: ALLOWABLE_OPERATORS
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| 224 | },
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| 225 | uniqueItems: true
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| 226 | }
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| 227 | },
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| 228 | additionalProperties: false
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| 229 | }],
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| 230 |
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| 231 | messages: {
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| 232 | useRecommendation: "use `{{recommendation}}` instead."
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| 233 | }
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| 234 | },
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| 235 |
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| 236 | create(context) {
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| 237 | const options = parseOptions(context.options[0] || {});
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| 238 | const sourceCode = context.sourceCode;
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| 239 |
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| 240 | /**
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| 241 | * Reports an error and autofixes the node
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| 242 | * @param {ASTNode} node An ast node to report the error on.
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| 243 | * @param {string} recommendation The recommended code for the issue
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| 244 | * @param {bool} shouldFix Whether this report should fix the node
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| 245 | * @returns {void}
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| 246 | */
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| 247 | function report(node, recommendation, shouldFix) {
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| 248 | context.report({
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| 249 | node,
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| 250 | messageId: "useRecommendation",
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| 251 | data: {
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| 252 | recommendation
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| 253 | },
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| 254 | fix(fixer) {
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| 255 | if (!shouldFix) {
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| 256 | return null;
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| 257 | }
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| 258 |
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| 259 | const tokenBefore = sourceCode.getTokenBefore(node);
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| 260 |
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| 261 | if (
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| 262 | tokenBefore &&
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| 263 | tokenBefore.range[1] === node.range[0] &&
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| 264 | !astUtils.canTokensBeAdjacent(tokenBefore, recommendation)
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| 265 | ) {
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| 266 | return fixer.replaceText(node, ` ${recommendation}`);
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| 267 | }
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| 268 | return fixer.replaceText(node, recommendation);
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| 269 | }
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| 270 | });
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| 271 | }
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| 272 |
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| 273 | return {
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| 274 | UnaryExpression(node) {
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| 275 | let operatorAllowed;
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| 276 |
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| 277 | // !!foo
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| 278 | operatorAllowed = options.allow.includes("!!");
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| 279 | if (!operatorAllowed && options.boolean && isDoubleLogicalNegating(node)) {
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| 280 | const recommendation = `Boolean(${sourceCode.getText(node.argument.argument)})`;
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| 281 |
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| 282 | report(node, recommendation, true);
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| 283 | }
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| 284 |
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| 285 | // ~foo.indexOf(bar)
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| 286 | operatorAllowed = options.allow.includes("~");
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| 287 | if (!operatorAllowed && options.boolean && isBinaryNegatingOfIndexOf(node)) {
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| 288 |
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| 289 | // `foo?.indexOf(bar) !== -1` will be true (== found) if the `foo` is nullish. So use `>= 0` in that case.
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| 290 | const comparison = node.argument.type === "ChainExpression" ? ">= 0" : "!== -1";
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| 291 | const recommendation = `${sourceCode.getText(node.argument)} ${comparison}`;
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| 292 |
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| 293 | report(node, recommendation, false);
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| 294 | }
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| 295 |
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| 296 | // +foo
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| 297 | operatorAllowed = options.allow.includes("+");
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| 298 | if (!operatorAllowed && options.number && node.operator === "+" && !isNumeric(node.argument)) {
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| 299 | const recommendation = `Number(${sourceCode.getText(node.argument)})`;
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| 300 |
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| 301 | report(node, recommendation, true);
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| 302 | }
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| 303 | },
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| 304 |
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| 305 | // Use `:exit` to prevent double reporting
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| 306 | "BinaryExpression:exit"(node) {
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| 307 | let operatorAllowed;
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| 308 |
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| 309 | // 1 * foo
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| 310 | operatorAllowed = options.allow.includes("*");
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| 311 | const nonNumericOperand = !operatorAllowed && options.number && isMultiplyByOne(node) && !isMultiplyByFractionOfOne(node, sourceCode) &&
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| 312 | getNonNumericOperand(node);
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| 313 |
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| 314 | if (nonNumericOperand) {
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| 315 | const recommendation = `Number(${sourceCode.getText(nonNumericOperand)})`;
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| 316 |
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| 317 | report(node, recommendation, true);
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| 318 | }
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| 319 |
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| 320 | // "" + foo
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| 321 | operatorAllowed = options.allow.includes("+");
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| 322 | if (!operatorAllowed && options.string && isConcatWithEmptyString(node)) {
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| 323 | const recommendation = `String(${sourceCode.getText(getNonEmptyOperand(node))})`;
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| 324 |
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| 325 | report(node, recommendation, true);
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| 326 | }
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| 327 | },
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| 328 |
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| 329 | AssignmentExpression(node) {
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| 330 |
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| 331 | // foo += ""
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| 332 | const operatorAllowed = options.allow.includes("+");
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| 333 |
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| 334 | if (!operatorAllowed && options.string && isAppendEmptyString(node)) {
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| 335 | const code = sourceCode.getText(getNonEmptyOperand(node));
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| 336 | const recommendation = `${code} = String(${code})`;
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| 337 |
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| 338 | report(node, recommendation, true);
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| 339 | }
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| 340 | },
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| 341 |
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| 342 | TemplateLiteral(node) {
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| 343 | if (!options.disallowTemplateShorthand) {
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| 344 | return;
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| 345 | }
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| 346 |
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| 347 | // tag`${foo}`
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| 348 | if (node.parent.type === "TaggedTemplateExpression") {
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| 349 | return;
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| 350 | }
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| 351 |
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| 352 | // `` or `${foo}${bar}`
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| 353 | if (node.expressions.length !== 1) {
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| 354 | return;
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| 355 | }
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| 356 |
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| 357 |
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| 358 | // `prefix${foo}`
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| 359 | if (node.quasis[0].value.cooked !== "") {
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| 360 | return;
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| 361 | }
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| 362 |
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| 363 | // `${foo}postfix`
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| 364 | if (node.quasis[1].value.cooked !== "") {
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| 365 | return;
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| 366 | }
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| 367 |
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| 368 | // if the expression is already a string, then this isn't a coercion
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| 369 | if (isStringType(node.expressions[0])) {
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| 370 | return;
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| 371 | }
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| 372 |
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| 373 | const code = sourceCode.getText(node.expressions[0]);
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| 374 | const recommendation = `String(${code})`;
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| 375 |
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| 376 | report(node, recommendation, true);
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| 377 | }
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| 378 | };
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| 379 | }
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| 380 | };
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