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no-unsafe-negation.js 4.62 KiB
/**
 * @fileoverview Rule to disallow negating the left operand of relational operators
 * @author Toru Nagashima
 */
"use strict";
//------------------------------------------------------------------------------
// Requirements
//------------------------------------------------------------------------------
const astUtils = require("./utils/ast-utils");
//------------------------------------------------------------------------------
// Helpers
//------------------------------------------------------------------------------
/**
 * Checks whether the given operator is `in` or `instanceof`
 * @param {string} op The operator type to check.
 * @returns {boolean} `true` if the operator is `in` or `instanceof`
function isInOrInstanceOfOperator(op) {
    return op === "in" || op === "instanceof";
/**
 * Checks whether the given operator is an ordering relational operator or not.
 * @param {string} op The operator type to check.
 * @returns {boolean} `true` if the operator is an ordering relational operator.
function isOrderingRelationalOperator(op) {
    return op === "<" || op === ">" || op === ">=" || op === "<=";
/**
 * Checks whether the given node is a logical negation expression or not.
 * @param {ASTNode} node The node to check.
 * @returns {boolean} `true` if the node is a logical negation expression.
function isNegation(node) {
    return node.type === "UnaryExpression" && node.operator === "!";
//------------------------------------------------------------------------------
// Rule Definition
//------------------------------------------------------------------------------
module.exports = {
    meta: {
        type: "problem",
        docs: {
            description: "disallow negating the left operand of relational operators",
            category: "Possible Errors",
            recommended: true,
            url: "https://eslint.org/docs/rules/no-unsafe-negation",
            suggestion: true
        schema: [
                type: "object",
                properties: {
                    enforceForOrderingRelations: {
                        type: "boolean",
                        default: false
                additionalProperties: false
} ], fixable: null, messages: { unexpected: "Unexpected negating the left operand of '{{operator}}' operator.", suggestNegatedExpression: "Negate '{{operator}}' expression instead of its left operand. This changes the current behavior.", suggestParenthesisedNegation: "Wrap negation in '()' to make the intention explicit. This preserves the current behavior." } }, create(context) { const sourceCode = context.getSourceCode(); const options = context.options[0] || {}; const enforceForOrderingRelations = options.enforceForOrderingRelations === true; return { BinaryExpression(node) { const operator = node.operator; const orderingRelationRuleApplies = enforceForOrderingRelations && isOrderingRelationalOperator(operator); if ( (isInOrInstanceOfOperator(operator) || orderingRelationRuleApplies) && isNegation(node.left) && !astUtils.isParenthesised(sourceCode, node.left) ) { context.report({ node, loc: node.left.loc, messageId: "unexpected", data: { operator }, suggest: [ { messageId: "suggestNegatedExpression", data: { operator }, fix(fixer) { const negationToken = sourceCode.getFirstToken(node.left); const fixRange = [negationToken.range[1], node.range[1]]; const text = sourceCode.text.slice(fixRange[0], fixRange[1]); return fixer.replaceTextRange(fixRange, `(${text})`); } }, { messageId: "suggestParenthesisedNegation", fix(fixer) { return fixer.replaceText(node.left, `(${sourceCode.getText(node.left)})`); } } ] }); } } }; } };