fix(ext/dom_exception): align better with spec

cli/tests/unit/dom_exception_test.ts

@@ -1,4 +1,8 @@
-import { assertEquals, assertStringIncludes } from "./test_util.ts";
+import {
+  assertEquals,
+  assertNotEquals,
+  assertStringIncludes,
+} from "./test_util.ts";
 
 Deno.test(function customInspectFunction() {
   const blob = new DOMException("test");
@@ -8,3 +12,13 @@ Deno.test(function customInspectFunction() {
   );
   assertStringIncludes(Deno.inspect(DOMException.prototype), "DOMException");
 });
+
+Deno.test(function nameToCodeMappingPrototypeAccess() {
+  const newCode = 100;
+  const objectPrototype = Object.prototype as unknown as {
+    pollution: number;
+  };
+  objectPrototype.pollution = newCode;
+  assertNotEquals(newCode, new DOMException("test", "pollution").code);
+  Reflect.deleteProperty(objectPrototype, "pollution");
+});

ext/web/01_dom_exception.js

@@ -18,13 +18,18 @@
     ObjectEntries,
     ObjectPrototypeIsPrototypeOf,
     ObjectSetPrototypeOf,
+    Symbol,
     SymbolFor,
   } = window.__bootstrap.primordials;
   const webidl = window.__bootstrap.webidl;
   const consoleInternal = window.__bootstrap.console;
 
+  const _name = Symbol("name");
+  const _message = Symbol("message");
+  const _code = Symbol("code");
+
   // Defined in WebIDL 4.3.
-  // https://heycam.github.io/webidl/#idl-DOMException
+  // https://webidl.spec.whatwg.org/#idl-DOMException
   const INDEX_SIZE_ERR = 1;
   const DOMSTRING_SIZE_ERR = 2;
   const HIERARCHY_REQUEST_ERR = 3;
@@ -52,9 +57,10 @@
   const DATA_CLONE_ERR = 25;
 
   // Defined in WebIDL 2.8.1.
-  // https://heycam.github.io/webidl/#dfn-error-names-table
+  // https://webidl.spec.whatwg.org/#dfn-error-names-table
   /** @type {Record<string, number>} */
   const nameToCodeMapping = {
+    __proto__: null,
     IndexSizeError: INDEX_SIZE_ERR,
     HierarchyRequestError: HIERARCHY_REQUEST_ERR,
     WrongDocumentError: WRONG_DOCUMENT_ERR,
@@ -80,24 +86,30 @@
   };
 
   // Defined in WebIDL 4.3.
-  // https://heycam.github.io/webidl/#idl-DOMException
+  // https://webidl.spec.whatwg.org/#idl-DOMException
   class DOMException {
-    #message = "";
-    #name = "";
-    #code = 0;
+    [_message];
+    [_name];
+    [_code];
 
+    // https://webidl.spec.whatwg.org/#dom-domexception-domexception
     constructor(message = "", name = "Error") {
-      this.#message = webidl.converters.DOMString(message, {
+      message = webidl.converters.DOMString(message, {
         prefix: "Failed to construct 'DOMException'",
         context: "Argument 1",
       });
-      this.#name = webidl.converters.DOMString(name, {
+      name = webidl.converters.DOMString(name, {
         prefix: "Failed to construct 'DOMException'",
         context: "Argument 2",
       });
-      this.#code = nameToCodeMapping[this.#name] ?? 0;
+      const code = nameToCodeMapping[name] ?? 0;
+
+      this[_message] = message;
+      this[_name] = name;
+      this[_code] = code;
+      this[webidl.brand] = webidl.brand;
 
-      const error = new Error(this.#message);
+      const error = new Error(message);
       error.name = "DOMException";
       ObjectDefineProperty(this, "stack", {
         value: error.stack,
@@ -115,20 +127,23 @@
     }
 
     get message() {
-      return this.#message;
+      webidl.assertBranded(this, DOMExceptionPrototype);
+      return this[_message];
     }
 
     get name() {
-      return this.#name;
+      webidl.assertBranded(this, DOMExceptionPrototype);
+      return this[_name];
     }
 
     get code() {
-      return this.#code;
+      webidl.assertBranded(this, DOMExceptionPrototype);
+      return this[_code];
     }
 
     [SymbolFor("Deno.customInspect")](inspect) {
       if (ObjectPrototypeIsPrototypeOf(DOMExceptionPrototype, this)) {
-        return `DOMException: ${this.#message}`;
+        return `DOMException: ${this[_message]}`;
       } else {
         return inspect(consoleInternal.createFilteredInspectProxy({
           object: this,