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Wolfgang Knopki authoredThis reverts commit f83b6c2a, reversing changes made to c2b73ce6.
08d3a3ba
/** * @fileoverview Rule to flag comparisons to the value NaN * @author James Allardice */"use strict";//------------------------------------------------------------------------------// Requirements//------------------------------------------------------------------------------const astUtils = require("./utils/ast-utils");//------------------------------------------------------------------------------// Helpers//------------------------------------------------------------------------------/** * Determines if the given node is a NaN `Identifier` node. * @param {ASTNode|null} node The node to check. * @returns {boolean} `true` if the node is 'NaN' identifier. */function isNaNIdentifier(node) { return Boolean(node) && ( astUtils.isSpecificId(node, "NaN") || astUtils.isSpecificMemberAccess(node, "Number", "NaN") );}//------------------------------------------------------------------------------// Rule Definition//------------------------------------------------------------------------------module.exports = { meta: { type: "problem", docs: { description: "require calls to `isNaN()` when checking for `NaN`", category: "Possible Errors", recommended: true, url: "https://eslint.org/docs/rules/use-isnan" }, schema: [ { type: "object", properties: { enforceForSwitchCase: { type: "boolean", default: true }, enforceForIndexOf: { type: "boolean", default: false } }, additionalProperties: false } ], messages: { comparisonWithNaN: "Use the isNaN function to compare with NaN.", switchNaN: "'switch(NaN)' can never match a case clause. Use Number.isNaN instead of the switch.", caseNaN: "'case NaN' can never match. Use Number.isNaN before the switch.", indexOfNaN: "Array prototype method '{{ methodName }}' cannot find NaN." } }, create(context) {
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const enforceForSwitchCase = !context.options[0] || context.options[0].enforceForSwitchCase;
const enforceForIndexOf = context.options[0] && context.options[0].enforceForIndexOf;
/**
* Checks the given `BinaryExpression` node for `foo === NaN` and other comparisons.
* @param {ASTNode} node The node to check.
* @returns {void}
*/
function checkBinaryExpression(node) {
if (
/^(?:[<>]|[!=]=)=?$/u.test(node.operator) &&
(isNaNIdentifier(node.left) || isNaNIdentifier(node.right))
) {
context.report({ node, messageId: "comparisonWithNaN" });
}
}
/**
* Checks the discriminant and all case clauses of the given `SwitchStatement` node for `switch(NaN)` and `case NaN:`
* @param {ASTNode} node The node to check.
* @returns {void}
*/
function checkSwitchStatement(node) {
if (isNaNIdentifier(node.discriminant)) {
context.report({ node, messageId: "switchNaN" });
}
for (const switchCase of node.cases) {
if (isNaNIdentifier(switchCase.test)) {
context.report({ node: switchCase, messageId: "caseNaN" });
}
}
}
/**
* Checks the given `CallExpression` node for `.indexOf(NaN)` and `.lastIndexOf(NaN)`.
* @param {ASTNode} node The node to check.
* @returns {void}
*/
function checkCallExpression(node) {
const callee = astUtils.skipChainExpression(node.callee);
if (callee.type === "MemberExpression") {
const methodName = astUtils.getStaticPropertyName(callee);
if (
(methodName === "indexOf" || methodName === "lastIndexOf") &&
node.arguments.length === 1 &&
isNaNIdentifier(node.arguments[0])
) {
context.report({ node, messageId: "indexOfNaN", data: { methodName } });
}
}
}
const listeners = {
BinaryExpression: checkBinaryExpression
};
if (enforceForSwitchCase) {
listeners.SwitchStatement = checkSwitchStatement;
}
if (enforceForIndexOf) {
listeners.CallExpression = checkCallExpression;
}
return listeners;
}