[dart2js] Use symbols for isolate tags

All supported browsers have JavaScript Symbols so use Symbols.
Avoiding string property names should fix a bug where separate
programs running in separate iframes arrive at using the same
property.

Issue: #53154
Change-Id: I470dc47de3ad381aeab670cf62d62e53f2e72873
Reviewed-on: https://dart-review.googlesource.com/c/sdk/+/319865
Reviewed-by: Sigmund Cherem <sigmund@google.com>
Commit-Queue: Stephen Adams <sra@google.com>

pkg/compiler/lib/src/js_emitter/js_emitter.dart

@@ -11,6 +11,5 @@ export 'interceptor_stub_generator.dart';
 export 'main_call_stub_generator.dart';
 export 'metadata_collector.dart';
 export 'native_emitter.dart';
-export 'native_generator.dart';
 export 'parameter_stub_generator.dart';
 export 'runtime_type_generator.dart';

pkg/compiler/lib/src/js_emitter/native_generator.dart

@@ -1,77 +0,0 @@
-// Copyright (c) 2014, the Dart project authors.  Please see the AUTHORS file
-// for details. All rights reserved. Use of this source code is governed by a
-// BSD-style license that can be found in the LICENSE file.
-
-library dart2js.js_emitter.native_generator;
-
-import 'package:js_runtime/synced/embedded_names.dart' as embeddedNames;
-
-import '../js/js.dart' as jsAst;
-import '../js/js.dart' show js;
-import '../js_backend/backend_usage.dart' show BackendUsage;
-
-class NativeGenerator {
-  static bool needsIsolateAffinityTagInitialization(BackendUsage backendUsage) {
-    return backendUsage.needToInitializeIsolateAffinityTag;
-  }
-
-  /// Generates the code for isolate affinity tags.
-  ///
-  /// Independently Dart programs on the same page must not interfere and
-  /// this code sets up the variables needed to guarantee that behavior.
-  static jsAst.Statement generateIsolateAffinityTagInitialization(
-      BackendUsage backendUsage,
-      jsAst.Expression generateEmbeddedGlobalAccess(String global),
-      jsAst.Expression internStringFunction) {
-    assert(backendUsage.needToInitializeIsolateAffinityTag);
-
-    jsAst.Expression getIsolateTagAccess =
-        generateEmbeddedGlobalAccess(embeddedNames.GET_ISOLATE_TAG);
-    jsAst.Expression isolateTagAccess =
-        generateEmbeddedGlobalAccess(embeddedNames.ISOLATE_TAG);
-    jsAst.Expression dispatchPropertyNameAccess =
-        generateEmbeddedGlobalAccess(embeddedNames.DISPATCH_PROPERTY_NAME);
-
-    return js.statement('''
-      !function() {
-        var intern = #internStringFunction;
-
-        #getIsolateTag = function(name) {
-          return intern("___dart_" + name + #isolateTag);
-        };
-
-        // To ensure that different programs loaded into the same context (page)
-        // use distinct dispatch properties, we place an object on `Object` to
-        // contain the names already in use.
-        var tableProperty = "___dart_isolate_tags_";
-        var usedProperties = Object[tableProperty] ||
-            (Object[tableProperty] = Object.create(null));
-
-        var rootProperty = "_${generateIsolateTagRoot()}";
-        for (var i = 0; ; i++) {
-          var property = intern(rootProperty + "_" + i + "_");
-          if (!(property in usedProperties)) {
-            usedProperties[property] = 1;
-            #isolateTag = property;
-            break;
-          }
-        }
-        if (#initializeDispatchProperty) {
-          #dispatchPropertyName = #getIsolateTag("dispatch_record");
-        }
-      }();
-    ''', {
-      'initializeDispatchProperty':
-          backendUsage.needToInitializeDispatchProperty,
-      'internStringFunction': internStringFunction,
-      'getIsolateTag': getIsolateTagAccess,
-      'isolateTag': isolateTagAccess,
-      'dispatchPropertyName': dispatchPropertyNameAccess
-    });
-  }
-
-  static String generateIsolateTagRoot() {
-    // TODO(sra): MD5 of contributing source code or URIs?
-    return 'ZxYxX';
-  }
-}

pkg/compiler/lib/src/js_emitter/startup_emitter/fragment_emitter.dart

@@ -1900,6 +1900,11 @@ class FragmentEmitter {
           js.string(RECORD_TYPE_TEST_COMBINATORS_PROPERTY), recordStubs));
     }
 
+    if (_closedWorld.backendUsage.needToInitializeDispatchProperty) {
+      globals.add(js.Property(js.string(DISPATCH_PROPERTY_NAME),
+          js.js('Symbol("dispatch_property")')));
+    }
+
     js.ObjectInitializer globalsObject =
         js.ObjectInitializer(globals, isOneLiner: false);
 
@@ -2060,22 +2065,6 @@ class FragmentEmitter {
   js.Statement emitNativeSupport(Fragment fragment) {
     List<js.Statement> statements = [];
 
-    // The isolate-affinity tag must only be initialized once per program.
-    if (fragment.isMainFragment &&
-        NativeGenerator.needsIsolateAffinityTagInitialization(
-            _closedWorld.backendUsage)) {
-      statements.add(NativeGenerator.generateIsolateAffinityTagInitialization(
-          _closedWorld.backendUsage, generateEmbeddedGlobalAccess, js.js("""
-        // On V8, the 'intern' function converts a string to a symbol, which
-        // makes property access much faster.
-        // TODO(sra): Use Symbol on non-IE11 browsers.
-        function (s) {
-          var o = {};
-          o[s] = 1;
-          return Object.keys(hunkHelpers.convertToFastObject(o))[0];
-        }""", [])));
-    }
-
     Map<String, js.Expression> interceptorsByTag = {};
     Map<String, js.Expression> leafTags = {};
     List<js.Statement> subclassAssignments = [];

pkg/compiler/lib/src/js_emitter/startup_emitter/model_emitter.dart

@@ -12,6 +12,7 @@ import 'package:js_runtime/synced/embedded_names.dart'
         DEFERRED_LIBRARY_PARTS,
         DEFERRED_PART_URIS,
         DEFERRED_PART_HASHES,
+        DISPATCH_PROPERTY_NAME,
         INITIALIZATION_EVENT_LOG,
         INITIALIZE_LOADED_HUNK,
         INTERCEPTORS_BY_TAG,

sdk/lib/_internal/js_runtime/lib/interceptors.dart

@@ -66,17 +66,17 @@ part 'js_array.dart';
 part 'js_number.dart';
 part 'js_string.dart';
 
-final String DART_CLOSURE_PROPERTY_NAME =
+final JavaScriptSymbol DART_CLOSURE_PROPERTY_NAME =
     getIsolateAffinityTag(r'_$dart_dartClosure');
 
 getDispatchProperty(object) {
-  return JS(
-      '', '#[#]', object, JS_EMBEDDED_GLOBAL('String', DISPATCH_PROPERTY_NAME));
+  return JS('', '#[#]', object,
+      JS_EMBEDDED_GLOBAL('JavaScriptSymbol', DISPATCH_PROPERTY_NAME));
 }
 
 setDispatchProperty(object, value) {
-  defineProperty(
-      object, JS_EMBEDDED_GLOBAL('String', DISPATCH_PROPERTY_NAME), value);
+  defineProperty(object,
+      JS_EMBEDDED_GLOBAL('JavaScriptSymbol', DISPATCH_PROPERTY_NAME), value);
 }
 
 // Avoid inlining this method because inlining gives us multiple allocation
@@ -191,11 +191,8 @@ getNativeInterceptor(object) {
   return JS_INTERCEPTOR_CONSTANT(UnknownJavaScriptObject);
 }
 
-// A JS String or Symbol.
-dynamic _JS_INTEROP_INTERCEPTOR_TAG = null;
-get JS_INTEROP_INTERCEPTOR_TAG {
-  return _JS_INTEROP_INTERCEPTOR_TAG ??= getIsolateAffinityTag(r'_$dart_js');
-}
+final JavaScriptSymbol JS_INTEROP_INTERCEPTOR_TAG =
+    getIsolateAffinityTag(r'_$dart_js');
 
 lookupInterceptorByConstructor(constructor) {
   return constructor == null

sdk/lib/_internal/js_runtime/lib/js_helper.dart

@@ -2808,15 +2808,12 @@ String jsonEncodeNative(String string) {
   return JS('String', 'JSON.stringify(#)', string);
 }
 
-/// Returns a property name for placing data on JavaScript objects shared
-/// between DOM isolates.  This happens when multiple programs are loaded in the
-/// same JavaScript context (i.e. page).  The name is based on [name] but with
-/// an additional part that is unique for each isolate.
-///
-/// The form of the name is '___dart_$name_$id'.
-String getIsolateAffinityTag(String name) {
-  var isolateTagGetter = JS_EMBEDDED_GLOBAL('', GET_ISOLATE_TAG);
-  return JS('String', '#(#)', isolateTagGetter, name);
+/// Returns a property symbol for this isolate to place private data on
+/// JavaScript objects where we need to avoid other isolates from seeing the
+/// data.  This happens when multiple programs are loaded in the same JavaScript
+/// context (i.e. page).  The property is based on [name].
+JavaScriptSymbol getIsolateAffinityTag(String name) {
+  return JS('JavaScriptSymbol', 'Symbol(#)', name);
 }
 
 final Map<String, Completer<Null>?> _loadingLibraries = {};

sdk/lib/_internal/js_runtime/lib/js_patch.dart

@@ -7,7 +7,7 @@ import 'dart:collection' show HashMap, ListMixin;
 import 'dart:typed_data' show TypedData;
 
 import 'dart:_foreign_helper' show JS, DART_CLOSURE_TO_JS;
-import 'dart:_interceptors' show DART_CLOSURE_PROPERTY_NAME;
+import 'dart:_interceptors' show DART_CLOSURE_PROPERTY_NAME, JavaScriptSymbol;
 import 'dart:_internal' show patch;
 import 'dart:_js_helper'
     show
@@ -17,6 +17,10 @@ import 'dart:_js_helper'
         JS_FUNCTION_PROPERTY_NAME;
 import 'dart:_js' show isBrowserObject, convertFromBrowserObject;
 
+// TODO(sra): Replace with an extension type when they become available.
+
+typedef _JavaScriptProperty = Object; // String | JavaScriptSymbol
+
 @patch
 JsObject get context => _context;
 
@@ -371,7 +375,7 @@ class JsArray<E> /*extends JsObject with ListMixin<E>*/ {
 }
 
 // property added to a Dart object referencing its JS-side DartObject proxy
-final String _DART_OBJECT_PROPERTY_NAME =
+final JavaScriptSymbol _DART_OBJECT_PROPERTY_NAME =
     getIsolateAffinityTag(r'_$dart_dartObject');
 
 // property added to a JS object referencing its Dart-side JsObject proxy
@@ -380,7 +384,7 @@ const _JS_OBJECT_PROPERTY_NAME = r'_$dart_jsObject';
 @pragma('dart2js:tryInline')
 JsObject _castToJsObject(o) => JS<JsObject>('', '#', o);
 
-bool _defineProperty(o, String name, value) {
+bool _defineProperty(o, _JavaScriptProperty name, value) {
   try {
     if (_isExtensible(o) &&
         // TODO(ahe): Calling _hasOwnProperty to work around
@@ -397,13 +401,13 @@ bool _defineProperty(o, String name, value) {
   return false;
 }
 
-bool _hasOwnProperty(o, String name) {
+bool _hasOwnProperty(o, _JavaScriptProperty name) {
   return JS('bool', 'Object.prototype.hasOwnProperty.call(#, #)', o, name);
 }
 
 bool _isExtensible(o) => JS('bool', 'Object.isExtensible(#)', o);
 
-Object? _getOwnProperty(o, String name) {
+Object? _getOwnProperty(o, _JavaScriptProperty name) {
   if (_hasOwnProperty(o, name)) {
     return JS('', '#[#]', o, name);
   }
@@ -491,8 +495,8 @@ Object _wrapToDart(o) {
       o, _DART_OBJECT_PROPERTY_NAME, (o) => JsObject._fromJs(o));
 }
 
-Object _getDartProxy(o, String propertyName, JsObject createProxy(o)) {
-  var dartProxy = _getOwnProperty(o, propertyName);
+Object _getDartProxy(o, _JavaScriptProperty property, JsObject createProxy(o)) {
+  var dartProxy = _getOwnProperty(o, property);
   // Temporary fix for dartbug.com/15193
   // In some cases it's possible to see a JavaScript object that
   // came from a different context and was previously proxied to
@@ -502,7 +506,7 @@ Object _getDartProxy(o, String propertyName, JsObject createProxy(o)) {
   // to cache proxies from multiple JS contexts and Dart isolates.
   if (dartProxy == null || !_isLocalObject(o)) {
     dartProxy = createProxy(o);
-    _defineProperty(o, propertyName, dartProxy);
+    _defineProperty(o, property, dartProxy);
   }
   return dartProxy;
 }

sdk/lib/_internal/js_runtime/lib/native_helper.dart

@@ -68,7 +68,8 @@ String toStringForNativeObject(var obj) {
 int hashCodeForNativeObject(object) => Primitives.objectHashCode(object);
 
 /// Sets a JavaScript property on an object.
-void defineProperty(var obj, String property, var value) {
+void defineProperty(
+    var obj, Object /*String | JavaScriptSymbol*/ property, var value) {
   JS(
       'void',
       'Object.defineProperty(#, #, '