no-constant-condition.js
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/**
* @fileoverview Rule to flag use constant conditions
* @author Christian Schulz <http://rndm.de>
* @copyright 2014 Christian Schulz. All rights reserved.
*/
"use strict";
//------------------------------------------------------------------------------
// Rule Definition
//------------------------------------------------------------------------------
module.exports = function(context) {
//--------------------------------------------------------------------------
// Helpers
//--------------------------------------------------------------------------
/**
* Checks if a node has a constant truthiness value.
* @param {ASTNode} node The AST node to check.
* @returns {Bool} true when node's truthiness is constant
* @private
*/
function isConstant(node) {
switch (node.type) {
case "Literal":
case "ArrowFunctionExpression":
case "FunctionExpression":
case "ObjectExpression":
case "ArrayExpression":
return true;
case "UnaryExpression":
return isConstant(node.argument);
case "BinaryExpression":
case "LogicalExpression":
return isConstant(node.left) && isConstant(node.right);
case "AssignmentExpression":
return (node.operator === "=") && isConstant(node.right);
case "SequenceExpression":
return isConstant(node.expressions[node.expressions.length - 1]);
// no default
}
return false;
}
/**
* Reports when the given node contains a constant condition.
* @param {ASTNode} node The AST node to check.
* @returns {void}
* @private
*/
function checkConstantCondition(node) {
if (node.test && isConstant(node.test)) {
context.report(node, "Unexpected constant condition.");
}
}
//--------------------------------------------------------------------------
// Public
//--------------------------------------------------------------------------
return {
"ConditionalExpression": checkConstantCondition,
"IfStatement": checkConstantCondition,
"WhileStatement": checkConstantCondition,
"DoWhileStatement": checkConstantCondition,
"ForStatement": checkConstantCondition
};
};
module.exports.schema = [];