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/**
* @fileoverview Rule to
* @author Toru Nagashima
*/
"use strict";
//------------------------------------------------------------------------------
// Helpers
//------------------------------------------------------------------------------
/**
* Gets the variable object of `arguments` which is defined implicitly.
* @param {eslint-scope.Scope} scope - A scope to get.
* @returns {eslint-scope.Variable} The found variable object.
*/
function getVariableOfArguments(scope) {
const variables = scope.variables;
for (let i = 0; i < variables.length; ++i) {
const variable = variables[i];
if (variable.name === "arguments") {
/*
* If there was a parameter which is named "arguments", the implicit "arguments" is not defined.
* So does fast return with null.
*/
return (variable.identifiers.length === 0) ? variable : null;
}
}
/* istanbul ignore next : unreachable */
return null;
}
/**
* Checks if the given reference is not normal member access.
*
* - arguments .... true // not member access
* - arguments[i] .... true // computed member access
* - arguments[0] .... true // computed member access
* - arguments.length .... false // normal member access
*
* @param {eslint-scope.Reference} reference - The reference to check.
* @returns {boolean} `true` if the reference is not normal member access.
*/
function isNotNormalMemberAccess(reference) {
const id = reference.identifier;
const parent = id.parent;
return !(
parent.type === "MemberExpression" &&
parent.object === id &&
!parent.computed
);
}
//------------------------------------------------------------------------------
// Rule Definition
//------------------------------------------------------------------------------
module.exports = {
meta: {
type: "suggestion",
docs: {
description: "require rest parameters instead of `arguments`",
category: "ECMAScript 6",
recommended: false,
url: "https://eslint.org/docs/rules/prefer-rest-params"
},
schema: []
},
create(context) {
/**
* Reports a given reference.
*
* @param {eslint-scope.Reference} reference - A reference to report.
* @returns {void}
*/
function report(reference) {
context.report({
node: reference.identifier,
loc: reference.identifier.loc,
message: "Use the rest parameters instead of 'arguments'."
});
}
/**
* Reports references of the implicit `arguments` variable if exist.
*
* @returns {void}
*/
function checkForArguments() {
const argumentsVar = getVariableOfArguments(context.getScope());
if (argumentsVar) {
argumentsVar
.references
.filter(isNotNormalMemberAccess)
.forEach(report);
}
}
return {
"FunctionDeclaration:exit": checkForArguments,
"FunctionExpression:exit": checkForArguments
};
}
};
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