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| /** | |
| * @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 } }); | |
| } | |
| } | |
| }; | |
| } | |
| }; |