Add WeakReference and Finalizer patches for ddc and dart2js

Routes implementation to JavaScript WeakRef and
FinalizerRegistry APIs using JS foreign function calls. Uses
Wrapper names for the Dart library to avoid issues with DDC.

Bug: #47775, #47776
Change-Id: Iad82bd83ac10c666d08a2c042a8ed6109b8b58c8
Reviewed-on: https://dart-review.googlesource.com/c/sdk/+/229180
Reviewed-by: Stephen Adams <[email protected]>
Reviewed-by: Sigmund Cherem <[email protected]>
Reviewed-by: Nicholas Shahan <[email protected]>
Commit-Queue: Riley Porter <[email protected]>

Author: rileyporter

sdk/lib/_internal/js_dev_runtime/patch/core_patch.dart

@@ -17,7 +17,8 @@ import 'dart:_js_helper'
         Primitives,
         PrivateSymbol,
         quoteStringForRegExp,
-        undefined;
+        undefined,
+        wrapZoneUnaryCallback;
 import 'dart:_runtime' as dart;
 import 'dart:_foreign_helper' show JS, JSExportName;
 import 'dart:_native_typed_data' show NativeUint8List;
@@ -165,19 +166,55 @@ class Expando<T extends Object> {
   }
 }
 
+// Patch for WeakReference implementation.
 @patch
 class WeakReference<T extends Object> {
   @patch
   factory WeakReference(T object) {
-    throw UnimplementedError("WeakReference");
+    return _WeakReferenceWrapper<T>(object);
   }
 }
 
+class _WeakReferenceWrapper<T extends Object> implements WeakReference<T> {
+  final Object _weakRef;
+
+  _WeakReferenceWrapper(T object)
+      : _weakRef = JS('!', 'new WeakRef(#)', object);
+
+  T? get target {
+    var target = JS<T?>('', '#.deref()', _weakRef);
+    // Coerce to null if JavaScript returns undefined.
+    if (JS<bool>('!', 'target === void 0')) return null;
+    return target;
+  }
+}
+
+// Patch for Finalizer implementation.
 @patch
 class Finalizer<T> {
   @patch
   factory Finalizer(void Function(T) object) {
-    throw UnimplementedError("Finalizer");
+    return _FinalizationRegistryWrapper<T>(object);
+  }
+}
+
+class _FinalizationRegistryWrapper<T> implements Finalizer<T> {
+  final Object _registry;
+
+  _FinalizationRegistryWrapper(void Function(T) callback)
+      : _registry = JS('!', 'new FinalizationRegistry(#)',
+            wrapZoneUnaryCallback(callback));
+
+  void attach(Object value, T token, {Object? detach}) {
+    if (detach != null) {
+      JS('', '#.register(#, #, #)', _registry, value, token, detach);
+    } else {
+      JS('', '#.register(#, #)', _registry, value, token);
+    }
+  }
+
+  void detach(Object detachToken) {
+    JS('', '#.unregister(#)', _registry, detachToken);
   }
 }
 

sdk/lib/_internal/js_dev_runtime/private/js_helper.dart

@@ -4,6 +4,7 @@
 
 library dart._js_helper;
 
+import 'dart:async' show Zone;
 import 'dart:collection';
 
 import 'dart:_foreign_helper' show JS, JSExportName;
@@ -828,3 +829,11 @@ void assertInterop(Object? value) {
 /// Like [assertInterop], except iterates over a list of arguments
 /// non-recursively.
 void assertInteropArgs(List<Object?> args) => args.forEach(assertInterop);
+
+/// Wraps the given [callback] within the current Zone.
+void Function(T)? wrapZoneUnaryCallback<T>(void Function(T)? callback) {
+  // For performance reasons avoid wrapping if we are in the root zone.
+  if (Zone.current == Zone.root) return callback;
+  if (callback == null) return null;
+  return Zone.current.bindUnaryCallbackGuarded(callback);
+}

sdk/lib/_internal/js_runtime/lib/core_patch.dart

@@ -13,6 +13,7 @@ import 'dart:_js_helper'
         checkInt,
         Closure,
         ConstantMap,
+        convertDartClosureToJS,
         getRuntimeType,
         JsLinkedHashMap,
         jsonEncodeNative,
@@ -23,7 +24,8 @@ import 'dart:_js_helper'
         quoteStringForRegExp,
         getTraceFromException,
         RuntimeError,
-        wrapException;
+        wrapException,
+        wrapZoneUnaryCallback;
 
 import 'dart:_foreign_helper' show JS;
 import 'dart:_native_typed_data' show NativeUint8List;
@@ -117,19 +119,49 @@ class Expando<T extends Object> {
   }
 }
 
+// Patch for WeakReference implementation.
 @patch
 class WeakReference<T extends Object> {
   @patch
   factory WeakReference(T object) {
-    throw UnimplementedError("WeakReference");
+    return _WeakReferenceWrapper<T>(object);
   }
 }
 
+class _WeakReferenceWrapper<T extends Object> implements WeakReference<T> {
+  final Object _weakRef;
+
+  _WeakReferenceWrapper(T object) : _weakRef = JS('', 'new WeakRef(#)', object);
+
+  T? get target => JS('', '#.deref()', _weakRef);
+}
+
+// Patch for Finalizer implementation.
 @patch
 class Finalizer<T> {
   @patch
   factory Finalizer(void Function(T) object) {
-    throw UnimplementedError("Finalizer");
+    return _FinalizationRegistryWrapper<T>(object);
+  }
+}
+
+class _FinalizationRegistryWrapper<T> implements Finalizer<T> {
+  final Object _registry;
+
+  _FinalizationRegistryWrapper(void Function(T) callback)
+      : _registry = JS('', 'new FinalizationRegistry(#)',
+            convertDartClosureToJS(wrapZoneUnaryCallback(callback), 1));
+
+  void attach(Object value, T token, {Object? detach}) {
+    if (detach != null) {
+      JS('', '#.register(#, #, #)', _registry, value, token, detach);
+    } else {
+      JS('', '#.register(#, #)', _registry, value, token);
+    }
+  }
+
+  void detach(Object detachToken) {
+    JS('', '#.unregister(#)', _registry, detachToken);
   }
 }
 

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

@@ -27,7 +27,7 @@ import 'dart:_js_embedded_names'
 
 import 'dart:collection';
 
-import 'dart:async' show Completer, DeferredLoadException, Future;
+import 'dart:async' show Completer, DeferredLoadException, Future, Zone;
 
 import 'dart:_foreign_helper'
     show
@@ -3029,3 +3029,11 @@ void assertInteropArgs(List<Object?> args) {
 Object? rawStartupMetrics() {
   return JS('JSArray', '#.a', JS_EMBEDDED_GLOBAL('', STARTUP_METRICS));
 }
+
+/// Wraps the given [callback] within the current Zone.
+void Function(T)? wrapZoneUnaryCallback<T>(void Function(T)? callback) {
+  // For performance reasons avoid wrapping if we are in the root zone.
+  if (Zone.current == Zone.root) return callback;
+  if (callback == null) return null;
+  return Zone.current.bindUnaryCallbackGuarded(callback);
+}

tests/web/weak_reference_test.dart

@@ -0,0 +1,55 @@
+// Copyright (c) 2022, 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.
+
+// Basic tests for the WeakReference and Finalizer API for the web backends.
+// Does not trigger garbage collection to heavily test the functionality.
+
+import 'package:expect/minitest.dart';
+
+class Foo {
+  int close() {
+    return 42; // no-op, dropped return value.
+  }
+}
+
+void callback(Foo f) {
+  f.close();
+}
+
+main() {
+  test('weak reference', () {
+    var list = ["foo"];
+    var weakRef = WeakReference<List<String>>(list);
+    expect(weakRef.target, equals(list));
+
+    // Javascript API throws when the representation of target is not 'object'
+    // in the compiled Javascript.
+    expect(() => WeakReference<String>("foo"), throws);
+    expect(() => WeakReference<int>(1), throws);
+  });
+
+  test('finalizer', () {
+    var finalizer = Finalizer<Foo>(callback);
+    var list = ["foo"];
+    var foo = Foo();
+    // Should not cause errors to attach or detach
+    finalizer.attach(list, foo);
+    finalizer.attach(list, foo, detach: list);
+    finalizer.detach(list);
+
+    // Should not cause errors to use a different detach token
+    var detachList = [1, 2, 3];
+    finalizer.attach(list, foo, detach: detachList);
+    finalizer.detach(detachList);
+
+    // JavaScript API returns false when unknown target detached.
+    // Should not cause an error to detach unknown token.
+    var unknownList = [2, 4, 6];
+    finalizer.detach(unknownList);
+
+    // JavaScript API throws when target and detach token are not objects.
+    expect(() => finalizer.attach("token string value", foo), throws);
+    expect(() => finalizer.detach("detach string value"), throws);
+  });
+}

tests/web/web.status

@@ -53,3 +53,6 @@ dummy_compiler_test: SkipByDesign # Issue 30773. Test should be migrated as a un
 [ $compiler == none && $runtime == vm ]
 new_from_env_test: SkipByDesign # dart2js only test
 unconditional_dartio_import_test: SkipByDesign # dart2js only test
+
+[ $compiler == dartkp || $runtime == vm ]
+weak_reference_test: SkipByDesign # Web only test

tests/web_2/weak_reference_test.dart

@@ -0,0 +1,55 @@
+// Copyright (c) 2022, 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.
+
+// Basic tests for the WeakReference and Finalizer API for the web backends.
+// Does not trigger garbage collection to heavily test the functionality.
+
+import 'package:expect/minitest.dart';
+
+class Foo {
+  int close() {
+    return 42; // no-op, dropped return value.
+  }
+}
+
+void callback(Foo f) {
+  f.close();
+}
+
+main() {
+  test('weak reference', () {
+    var list = ["foo"];
+    var weakRef = WeakReference<List<String>>(list);
+    expect(weakRef.target, equals(list));
+
+    // Javascript API throws when the representation of target is not 'object'
+    // in the compiled Javascript.
+    expect(() => WeakReference<String>("foo"), throws);
+    expect(() => WeakReference<int>(1), throws);
+  });
+
+  test('finalizer', () {
+    var finalizer = Finalizer<Foo>(callback);
+    var list = ["foo"];
+    var foo = Foo();
+    // Should not cause errors to attach or detach
+    finalizer.attach(list, foo);
+    finalizer.attach(list, foo, detach: list);
+    finalizer.detach(list);
+
+    // Should not cause errors to use a different detach token
+    var detachList = [1, 2, 3];
+    finalizer.attach(list, foo, detach: detachList);
+    finalizer.detach(detachList);
+
+    // JavaScript API returns false when unknown target detached.
+    // Should not cause an error to detach unknown token.
+    var unknownList = [2, 4, 6];
+    finalizer.detach(unknownList);
+
+    // JavaScript API throws when target and detach token are not objects.
+    expect(() => finalizer.attach("token string value", foo), throws);
+    expect(() => finalizer.detach("detach string value"), throws);
+  });
+}

tests/web_2/web_2.status

@@ -53,3 +53,6 @@ dummy_compiler_test: SkipByDesign # Issue 30773. Test should be migrated as a un
 [ $compiler == none && $runtime == vm ]
 new_from_env_test: SkipByDesign # dart2js only test
 unconditional_dartio_import_test: SkipByDesign # dart2js only test
+
+[ $compiler == dartkp || $runtime == vm ]
+weak_reference_test: SkipByDesign # Web only test