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105 lines
3.4 KiB
105 lines
3.4 KiB
/**
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* @fileoverview A rule to disallow unnecessary `.call()` and `.apply()`.
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* @author Toru Nagashima
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*/
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"use strict";
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var astUtils = require("../ast-utils");
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//------------------------------------------------------------------------------
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// Helpers
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//------------------------------------------------------------------------------
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/**
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* Checks whether or not a node is a `.call()`/`.apply()`.
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* @param {ASTNode} node - A CallExpression node to check.
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* @returns {boolean} Whether or not the node is a `.call()`/`.apply()`.
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*/
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function isCallOrNonVariadicApply(node) {
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return (
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node.callee.type === "MemberExpression" &&
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node.callee.property.type === "Identifier" &&
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node.callee.computed === false &&
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(
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(node.callee.property.name === "call" && node.arguments.length >= 1) ||
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(node.callee.property.name === "apply" && node.arguments.length === 2 && node.arguments[1].type === "ArrayExpression")
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)
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);
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}
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/**
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* Checks whether or not the tokens of two given nodes are same.
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* @param {ASTNode} left - A node 1 to compare.
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* @param {ASTNode} right - A node 2 to compare.
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* @param {RuleContext} context - The ESLint rule context object.
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* @returns {boolean} the source code for the given node.
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*/
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function equalTokens(left, right, context) {
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var tokensL = context.getTokens(left);
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var tokensR = context.getTokens(right);
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if (tokensL.length !== tokensR.length) {
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return false;
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}
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for (var i = 0; i < tokensL.length; ++i) {
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if (tokensL[i].type !== tokensR[i].type ||
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tokensL[i].value !== tokensR[i].value
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) {
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return false;
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}
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}
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return true;
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}
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/**
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* Checks whether or not `thisArg` is not changed by `.call()`/`.apply()`.
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* @param {ASTNode|null} expectedThis - The node that is the owner of the applied function.
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* @param {ASTNode} thisArg - The node that is given to the first argument of the `.call()`/`.apply()`.
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* @param {RuleContext} context - The ESLint rule context object.
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* @returns {boolean} Whether or not `thisArg` is not changed by `.call()`/`.apply()`.
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*/
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function isValidThisArg(expectedThis, thisArg, context) {
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if (!expectedThis) {
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return astUtils.isNullOrUndefined(thisArg);
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}
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return equalTokens(expectedThis, thisArg, context);
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}
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//------------------------------------------------------------------------------
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// Rule Definition
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//------------------------------------------------------------------------------
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module.exports = {
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meta: {
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docs: {
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description: "disallow unnecessary calls to `.call()` and `.apply()`",
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category: "Best Practices",
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recommended: false
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},
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schema: []
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},
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create: function(context) {
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return {
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CallExpression: function(node) {
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if (!isCallOrNonVariadicApply(node)) {
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return;
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}
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var applied = node.callee.object;
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var expectedThis = (applied.type === "MemberExpression") ? applied.object : null;
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var thisArg = node.arguments[0];
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if (isValidThisArg(expectedThis, thisArg, context)) {
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context.report(
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node,
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"unnecessary '.{{name}}()'.",
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{name: node.callee.property.name});
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}
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}
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};
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}
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};
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