--- /dev/null
+/**
+ * @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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