/**
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* @fileoverview Rule to disallow negating the left operand of relational operators
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* @author Toru Nagashima
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*/
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"use strict";
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//------------------------------------------------------------------------------
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// Requirements
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//------------------------------------------------------------------------------
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const astUtils = require("../util/ast-utils");
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//------------------------------------------------------------------------------
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// Helpers
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//------------------------------------------------------------------------------
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/**
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* Checks whether the given operator is a relational operator or not.
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*
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* @param {string} op - The operator type to check.
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* @returns {boolean} `true` if the operator is a relational operator.
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*/
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function isRelationalOperator(op) {
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return op === "in" || op === "instanceof";
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}
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/**
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* Checks whether the given node is a logical negation expression or not.
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*
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* @param {ASTNode} node - The node to check.
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* @returns {boolean} `true` if the node is a logical negation expression.
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*/
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function isNegation(node) {
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return node.type === "UnaryExpression" && node.operator === "!";
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}
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//------------------------------------------------------------------------------
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// Rule Definition
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//------------------------------------------------------------------------------
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module.exports = {
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meta: {
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type: "problem",
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docs: {
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description: "disallow negating the left operand of relational operators",
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category: "Possible Errors",
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recommended: true,
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url: "https://eslint.org/docs/rules/no-unsafe-negation"
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},
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schema: [],
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fixable: "code",
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messages: {
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unexpected: "Unexpected negating the left operand of '{{operator}}' operator."
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}
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},
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create(context) {
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const sourceCode = context.getSourceCode();
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return {
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BinaryExpression(node) {
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if (isRelationalOperator(node.operator) &&
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isNegation(node.left) &&
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!astUtils.isParenthesised(sourceCode, node.left)
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) {
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context.report({
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node,
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loc: node.left.loc,
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messageId: "unexpected",
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data: { operator: node.operator },
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fix(fixer) {
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const negationToken = sourceCode.getFirstToken(node.left);
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const fixRange = [negationToken.range[1], node.range[1]];
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const text = sourceCode.text.slice(fixRange[0], fixRange[1]);
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return fixer.replaceTextRange(fixRange, `(${text})`);
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}
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});
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}
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}
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};
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}
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};
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