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node_modules/eslint/lib/rules/no-extend-native.js

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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");
+
+//------------------------------------------------------------------------------
+// Helpers
+//------------------------------------------------------------------------------
+
+const propertyDefinitionMethods = new Set(["defineProperty", "defineProperties"]);
+
+//------------------------------------------------------------------------------
+// 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"
+            );
+        }
+
+        /**
+         * Checks that an identifier is an object of a prototype whose member
+         * is being assigned in an AssignmentExpression.
+         * Example: Object.prototype.foo = "bar"
+         * @param {ASTNode} identifierNode The identifier to check.
+         * @returns {boolean} True if the identifier's prototype is modified.
+         */
+        function isInPrototypePropertyAssignment(identifierNode) {
+            return Boolean(
+                isPrototypePropertyAccessed(identifierNode) &&
+                identifierNode.parent.parent.type === "MemberExpression" &&
+                identifierNode.parent.parent.parent.type === "AssignmentExpression" &&
+                identifierNode.parent.parent.parent.left === identifierNode.parent.parent
+            );
+        }
+
+        /**
+         * Checks that an identifier is an object of a prototype whose member
+         * is being extended via the Object.defineProperty() or
+         * Object.defineProperties() methods.
+         * Example: Object.defineProperty(Array.prototype, "foo", ...)
+         * Example: Object.defineProperties(Array.prototype, ...)
+         * @param {ASTNode} identifierNode The identifier to check.
+         * @returns {boolean} True if the identifier's prototype is modified.
+         */
+        function isInDefinePropertyCall(identifierNode) {
+            return Boolean(
+                isPrototypePropertyAccessed(identifierNode) &&
+                identifierNode.parent.parent.type === "CallExpression" &&
+                identifierNode.parent.parent.arguments[0] === identifierNode.parent &&
+                identifierNode.parent.parent.callee.type === "MemberExpression" &&
+                identifierNode.parent.parent.callee.object.type === "Identifier" &&
+                identifierNode.parent.parent.callee.object.name === "Object" &&
+                identifierNode.parent.parent.callee.property.type === "Identifier" &&
+                propertyDefinitionMethods.has(identifierNode.parent.parent.callee.property.name)
+            );
+        }
+
+        /**
+         * 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 (isInPrototypePropertyAssignment(identifierNode)) {
+
+                // Identifier --> MemberExpression --> MemberExpression --> AssignmentExpression
+                reportNode(identifierNode.parent.parent.parent, identifierNode.name);
+            } else if (isInDefinePropertyCall(identifierNode)) {
+
+                // Identifier --> MemberExpression --> CallExpression
+                reportNode(identifierNode.parent.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);
+                    }
+                });
+            }
+        };
+
+    }
+};