| /** |
| * @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) { |
| return ( |
| node.callee.type === "MemberExpression" && |
| node.callee.property.type === "Identifier" && |
| node.callee.computed === false && |
| ( |
| (node.callee.property.name === "call" && node.arguments.length >= 1) || |
| (node.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 |
| //------------------------------------------------------------------------------ |
| |
| module.exports = { |
| meta: { |
| type: "suggestion", |
| |
| docs: { |
| description: "disallow unnecessary calls to `.call()` and `.apply()`", |
| category: "Best Practices", |
| recommended: false, |
| url: "https://eslint.org/docs/rules/no-useless-call" |
| }, |
| |
| schema: [] |
| }, |
| |
| create(context) { |
| const sourceCode = context.getSourceCode(); |
| |
| return { |
| CallExpression(node) { |
| if (!isCallOrNonVariadicApply(node)) { |
| return; |
| } |
| |
| const applied = node.callee.object; |
| const expectedThis = (applied.type === "MemberExpression") ? applied.object : null; |
| const thisArg = node.arguments[0]; |
| |
| if (isValidThisArg(expectedThis, thisArg, sourceCode)) { |
| context.report({ node, message: "unnecessary '.{{name}}()'.", data: { name: node.callee.property.name } }); |
| } |
| } |
| }; |
| } |
| }; |