Skip to content
Permalink
9bfb9ba527
Switch branches/tags

Name already in use

A tag already exists with the provided branch name. Many Git commands accept both tag and branch names, so creating this branch may cause unexpected behavior. Are you sure you want to create this branch?
Go to file
 
 
Cannot retrieve contributors at this time
90 lines (74 sloc) 2.99 KB
/**
* @fileoverview A rule to disallow unnecessary `.call()` and `.apply()`.
* @author Toru Nagashima
*/
"use strict";
const astUtils = require("./utils/ast-utils");
//------------------------------------------------------------------------------
// Helpers
//------------------------------------------------------------------------------
/**
* Checks whether or not a node is a `.call()`/`.apply()`.
* @param {ASTNode} node A CallExpression node to check.
* @returns {boolean} Whether or not the node is a `.call()`/`.apply()`.
*/
function isCallOrNonVariadicApply(node) {
const callee = astUtils.skipChainExpression(node.callee);
return (
callee.type === "MemberExpression" &&
callee.property.type === "Identifier" &&
callee.computed === false &&
(
(callee.property.name === "call" && node.arguments.length >= 1) ||
(callee.property.name === "apply" && node.arguments.length === 2 && node.arguments[1].type === "ArrayExpression")
)
);
}
/**
* Checks whether or not `thisArg` is not changed by `.call()`/`.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 `.call()`/`.apply()`.
* @param {SourceCode} sourceCode The ESLint source code object.
* @returns {boolean} Whether or not `thisArg` is not changed by `.call()`/`.apply()`.
*/
function isValidThisArg(expectedThis, thisArg, sourceCode) {
if (!expectedThis) {
return astUtils.isNullOrUndefined(thisArg);
}
return astUtils.equalTokens(expectedThis, thisArg, sourceCode);
}
//------------------------------------------------------------------------------
// Rule Definition
//------------------------------------------------------------------------------
/** @type {import('../shared/types').Rule} */
module.exports = {
meta: {
type: "suggestion",
docs: {
description: "Disallow unnecessary calls to `.call()` and `.apply()`",
recommended: false,
url: "https://eslint.org/docs/latest/rules/no-useless-call"
},
schema: [],
messages: {
unnecessaryCall: "Unnecessary '.{{name}}()'."
}
},
create(context) {
const sourceCode = context.sourceCode;
return {
CallExpression(node) {
if (!isCallOrNonVariadicApply(node)) {
return;
}
const callee = astUtils.skipChainExpression(node.callee);
const applied = astUtils.skipChainExpression(callee.object);
const expectedThis = (applied.type === "MemberExpression") ? applied.object : null;
const thisArg = node.arguments[0];
if (isValidThisArg(expectedThis, thisArg, sourceCode)) {
context.report({ node, messageId: "unnecessaryCall", data: { name: callee.property.name } });
}
}
};
}
};