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/** * @fileoverview A rule to suggest using of the spread operator instead of `.apply()`. * @author Toru Nagashima */
"use strict";
const astUtils = require("./utils/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 ( astUtils.isSpecificMemberAccess(node.callee, null, "apply") && node.arguments.length === 2 && node.arguments[1].type !== "ArrayExpression" && node.arguments[1].type !== "SpreadElement" ); }
/** * 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 astUtils.equalTokens(expectedThis, thisArg, context); }
//------------------------------------------------------------------------------
// Rule Definition
//------------------------------------------------------------------------------
module.exports = { meta: { type: "suggestion",
docs: { description: "require spread operators instead of `.apply()`", category: "ECMAScript 6", recommended: false, url: "https://eslint.org/docs/rules/prefer-spread" },
schema: [], fixable: null,
messages: { preferSpread: "Use the spread operator instead of '.apply()'." } },
create(context) { const sourceCode = context.getSourceCode();
return { CallExpression(node) { if (!isVariadicApplyCalling(node)) { return; }
const applied = astUtils.skipChainExpression(astUtils.skipChainExpression(node.callee).object); const expectedThis = (applied.type === "MemberExpression") ? applied.object : null; const thisArg = node.arguments[0];
if (isValidThisArg(expectedThis, thisArg, sourceCode)) { context.report({ node, messageId: "preferSpread" }); } } }; } };
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