no-extra-boolean-cast.js
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/**
* @fileoverview Rule to flag unnecessary double negation in Boolean contexts
* @author Brandon Mills
*/
"use strict";
//------------------------------------------------------------------------------
// Rule Definition
//------------------------------------------------------------------------------
module.exports = function(context) {
return {
"UnaryExpression": function(node) {
var ancestors = context.getAncestors(),
parent = ancestors.pop(),
grandparent = ancestors.pop();
// Exit early if it's guaranteed not to match
if (node.operator !== "!" ||
parent.type !== "UnaryExpression" ||
parent.operator !== "!") {
return;
}
// if (<bool>) ...
if (grandparent.type === "IfStatement") {
context.report(node, "Redundant double negation in an if statement condition.");
// do ... while (<bool>)
} else if (grandparent.type === "DoWhileStatement") {
context.report(node, "Redundant double negation in a do while loop condition.");
// while (<bool>) ...
} else if (grandparent.type === "WhileStatement") {
context.report(node, "Redundant double negation in a while loop condition.");
// <bool> ? ... : ...
} else if ((grandparent.type === "ConditionalExpression" &&
parent === grandparent.test)) {
context.report(node, "Redundant double negation in a ternary condition.");
// for (...; <bool>; ...) ...
} else if ((grandparent.type === "ForStatement" &&
parent === grandparent.test)) {
context.report(node, "Redundant double negation in a for loop condition.");
// !<bool>
} else if ((grandparent.type === "UnaryExpression" &&
grandparent.operator === "!")) {
context.report(node, "Redundant multiple negation.");
// Boolean(<bool>)
} else if ((grandparent.type === "CallExpression" &&
grandparent.callee.type === "Identifier" &&
grandparent.callee.name === "Boolean")) {
context.report(node, "Redundant double negation in call to Boolean().");
// new Boolean(<bool>)
} else if ((grandparent.type === "NewExpression" &&
grandparent.callee.type === "Identifier" &&
grandparent.callee.name === "Boolean")) {
context.report(node, "Redundant double negation in Boolean constructor call.");
}
}
};
};
module.exports.schema = [];