prefer-spread.js
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/**
* @fileoverview A rule to suggest using of the spread operator instead of `.apply()`.
* @author Toru Nagashima
* @copyright 2015 Toru Nagashima. All rights reserved.
*/
"use strict";
var astUtils = require("../ast-utils");
//------------------------------------------------------------------------------
// Helpers
//------------------------------------------------------------------------------
/**
* Checks whether or not a node is a `.apply()` for variadic.
* @param {ASTNode} node - A CallExpression node to check.
* @returns {boolean} Whether or not the node is a `.apply()` for variadic.
*/
function isVariadicApplyCalling(node) {
return (
node.callee.type === "MemberExpression" &&
node.callee.property.type === "Identifier" &&
node.callee.property.name === "apply" &&
node.callee.computed === false &&
node.arguments.length === 2 &&
node.arguments[1].type !== "ArrayExpression"
);
}
/**
* Checks whether or not the tokens of two given nodes are same.
* @param {ASTNode} left - A node 1 to compare.
* @param {ASTNode} right - A node 2 to compare.
* @param {RuleContext} context - The ESLint rule context object.
* @returns {boolean} the source code for the given node.
*/
function equalTokens(left, right, context) {
var tokensL = context.getTokens(left);
var tokensR = context.getTokens(right);
if (tokensL.length !== tokensR.length) {
return false;
}
for (var i = 0; i < tokensL.length; ++i) {
if (tokensL[i].type !== tokensR[i].type ||
tokensL[i].value !== tokensR[i].value
) {
return false;
}
}
return true;
}
/**
* Checks whether or not `thisArg` is not changed by `.apply()`.
* @param {ASTNode|null} expectedThis - The node that is the owner of the applied function.
* @param {ASTNode} thisArg - The node that is given to the first argument of the `.apply()`.
* @param {RuleContext} context - The ESLint rule context object.
* @returns {boolean} Whether or not `thisArg` is not changed by `.apply()`.
*/
function isValidThisArg(expectedThis, thisArg, context) {
if (!expectedThis) {
return astUtils.isNullOrUndefined(thisArg);
}
return equalTokens(expectedThis, thisArg, context);
}
//------------------------------------------------------------------------------
// Rule Definition
//------------------------------------------------------------------------------
module.exports = function(context) {
return {
"CallExpression": function(node) {
if (!isVariadicApplyCalling(node)) {
return;
}
var applied = node.callee.object;
var expectedThis = (applied.type === "MemberExpression") ? applied.object : null;
var thisArg = node.arguments[0];
if (isValidThisArg(expectedThis, thisArg, context)) {
context.report(node, "use the spread operator instead of the \".apply()\".");
}
}
};
};
module.exports.schema = [];