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- /**
- * @fileoverview Rule to flag adding properties to native object's prototypes.
- * @author David Nelson
- */
- "use strict";
- //------------------------------------------------------------------------------
- // Requirements
- //------------------------------------------------------------------------------
- const astUtils = require("./utils/ast-utils");
- const globals = require("globals");
- //------------------------------------------------------------------------------
- // Rule Definition
- //------------------------------------------------------------------------------
- module.exports = {
- meta: {
- type: "suggestion",
- docs: {
- description: "disallow extending native types",
- category: "Best Practices",
- recommended: false,
- url: "https://eslint.org/docs/rules/no-extend-native"
- },
- schema: [
- {
- type: "object",
- properties: {
- exceptions: {
- type: "array",
- items: {
- type: "string"
- },
- uniqueItems: true
- }
- },
- additionalProperties: false
- }
- ],
- messages: {
- unexpected: "{{builtin}} prototype is read only, properties should not be added."
- }
- },
- create(context) {
- const config = context.options[0] || {};
- const exceptions = new Set(config.exceptions || []);
- const modifiedBuiltins = new Set(
- Object.keys(globals.builtin)
- .filter(builtin => builtin[0].toUpperCase() === builtin[0])
- .filter(builtin => !exceptions.has(builtin))
- );
- /**
- * Reports a lint error for the given node.
- * @param {ASTNode} node The node to report.
- * @param {string} builtin The name of the native builtin being extended.
- * @returns {void}
- */
- function reportNode(node, builtin) {
- context.report({
- node,
- messageId: "unexpected",
- data: {
- builtin
- }
- });
- }
- /**
- * Check to see if the `prototype` property of the given object
- * identifier node is being accessed.
- * @param {ASTNode} identifierNode The Identifier representing the object
- * to check.
- * @returns {boolean} True if the identifier is the object of a
- * MemberExpression and its `prototype` property is being accessed,
- * false otherwise.
- */
- function isPrototypePropertyAccessed(identifierNode) {
- return Boolean(
- identifierNode &&
- identifierNode.parent &&
- identifierNode.parent.type === "MemberExpression" &&
- identifierNode.parent.object === identifierNode &&
- astUtils.getStaticPropertyName(identifierNode.parent) === "prototype"
- );
- }
- /**
- * Check if it's an assignment to the property of the given node.
- * Example: `*.prop = 0` // the `*` is the given node.
- * @param {ASTNode} node The node to check.
- * @returns {boolean} True if an assignment to the property of the node.
- */
- function isAssigningToPropertyOf(node) {
- return (
- node.parent.type === "MemberExpression" &&
- node.parent.object === node &&
- node.parent.parent.type === "AssignmentExpression" &&
- node.parent.parent.left === node.parent
- );
- }
- /**
- * Checks if the given node is at the first argument of the method call of `Object.defineProperty()` or `Object.defineProperties()`.
- * @param {ASTNode} node The node to check.
- * @returns {boolean} True if the node is at the first argument of the method call of `Object.defineProperty()` or `Object.defineProperties()`.
- */
- function isInDefinePropertyCall(node) {
- return (
- node.parent.type === "CallExpression" &&
- node.parent.arguments[0] === node &&
- astUtils.isSpecificMemberAccess(node.parent.callee, "Object", /^definePropert(?:y|ies)$/u)
- );
- }
- /**
- * Check to see if object prototype access is part of a prototype
- * extension. There are three ways a prototype can be extended:
- * 1. Assignment to prototype property (Object.prototype.foo = 1)
- * 2. Object.defineProperty()/Object.defineProperties() on a prototype
- * If prototype extension is detected, report the AssignmentExpression
- * or CallExpression node.
- * @param {ASTNode} identifierNode The Identifier representing the object
- * which prototype is being accessed and possibly extended.
- * @returns {void}
- */
- function checkAndReportPrototypeExtension(identifierNode) {
- if (!isPrototypePropertyAccessed(identifierNode)) {
- return; // This is not `*.prototype` access.
- }
- /*
- * `identifierNode.parent` is a MemberExpression `*.prototype`.
- * If it's an optional member access, it may be wrapped by a `ChainExpression` node.
- */
- const prototypeNode =
- identifierNode.parent.parent.type === "ChainExpression"
- ? identifierNode.parent.parent
- : identifierNode.parent;
- if (isAssigningToPropertyOf(prototypeNode)) {
- // `*.prototype` -> MemberExpression -> AssignmentExpression
- reportNode(prototypeNode.parent.parent, identifierNode.name);
- } else if (isInDefinePropertyCall(prototypeNode)) {
- // `*.prototype` -> CallExpression
- reportNode(prototypeNode.parent, identifierNode.name);
- }
- }
- return {
- "Program:exit"() {
- const globalScope = context.getScope();
- modifiedBuiltins.forEach(builtin => {
- const builtinVar = globalScope.set.get(builtin);
- if (builtinVar && builtinVar.references) {
- builtinVar.references
- .map(ref => ref.identifier)
- .forEach(checkAndReportPrototypeExtension);
- }
- });
- }
- };
- }
- };
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