/**
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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("./utils/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 `in` or `instanceof`
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* @param {string} op The operator type to check.
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* @returns {boolean} `true` if the operator is `in` or `instanceof`
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*/
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function isInOrInstanceOfOperator(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 operator is an ordering relational operator or not.
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* @param {string} op The operator type to check.
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* @returns {boolean} `true` if the operator is an ordering relational operator.
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*/
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function isOrderingRelationalOperator(op) {
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return op === "<" || op === ">" || op === ">=" || op === "<=";
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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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* @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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{
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type: "object",
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properties: {
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enforceForOrderingRelations: {
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type: "boolean",
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default: false
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}
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},
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additionalProperties: false
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}
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],
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fixable: null,
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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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const options = context.options[0] || {};
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const enforceForOrderingRelations = options.enforceForOrderingRelations === true;
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return {
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BinaryExpression(node) {
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const orderingRelationRuleApplies = enforceForOrderingRelations && isOrderingRelationalOperator(node.operator);
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if (
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(isInOrInstanceOfOperator(node.operator) || orderingRelationRuleApplies) &&
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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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});
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}
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}
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};
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}
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};
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