Add typings for JSRecord and some unsafe extensions for JSObject

js_interop/lib/js_interop.dart

@@ -3,4 +3,6 @@
 // BSD-style license that can be found in the LICENSE file.
 
 export 'src/dart/date_time.dart';
+export 'src/dart/map.dart';
 export 'src/date.dart';
+export 'src/record.dart';

js_interop/lib/src/dart/map.dart

@@ -0,0 +1,13 @@
+// Copyright (c) 2025, 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.p
+
+import 'dart:js_interop';
+
+import '../record.dart';
+
+/// Conversion from [Map] to [JSRecord].
+extension MapToJSRecord<V extends JSAny?> on Map<String, V> {
+  /// Converts [this] to a [JSRecord] by cloning it.
+  JSRecord<V> get toJSRecord => JSRecord.ofMap<V>(this);
+}

js_interop/lib/src/record.dart

@@ -0,0 +1,192 @@
+// Copyright (c) 2025, 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.
+
+import 'dart:js_interop';
+import 'dart:js_interop_unsafe';
+
+import 'unsafe/object.dart';
+
+/// A JavaScript "record type", or in other words an object that's used as a
+/// lightweight map.
+///
+/// This provides a map-like API and utilities for interacting with records, as
+/// well as a [toDart] method for converting it into a true map. It considers
+/// the object's keys to be its enumerable, own, string properties (following
+/// `Object.keys()`).
+///
+/// In most cases, JS records only accept string keys, and this type is
+/// optimized to make this case easy to work with by automatically wrapping and
+/// unwrapping [JSString]s. However, there are cases where [JSSymbol]s are used
+/// as keys, in which case [JSSymbolicRecord] may be used instead.
+///
+/// Because this is a JavaScript object it follows JavaScript ordering
+/// semantics. Specifically: all number-like keys come first in numeric order,
+/// then all string keys in insertion order.
+///
+/// **Note:** Like Dart collections, it's not guaranteed to be safe to modify
+/// this while iterating over it. Unlike Dart collections, it doesn't have any
+/// fail-safes to throw errors if this happens. So be extra careful!
+extension type JSRecord<V extends JSAny?>._(JSObject _) implements JSObject {
+  /// Returns an iterable over tuples of the `key`/`value` pairs in this record.
+  Iterable<(String, V)> get pairs =>
+      JSObjectUnsafeExtension(this).entries.cast<(String, V)>();
+
+  /// See [Map.entries].
+  Iterable<MapEntry<String, V>> get entries sync* {
+    for (var (key, value) in pairs) {
+      yield MapEntry(key, value);
+    }
+  }
+
+  /// See [Map.isEmpty].
+  bool get isEmpty => length == 0;
+
+  /// See [Map.isNotEmpty].
+  bool get isNotEmpty => length != 0;
+
+  /// See [Map.keys].
+  Iterable<String> get keys sync* {
+    for (var key in JSObjectUnsafeExtension(this).keys) {
+      yield key.toDart;
+    }
+  }
+
+  /// See [Map.length].
+  int get length => JSObjectUnsafeExtension(this).keys.length;
+
+  /// See [Map.values].
+  Iterable<V> get values => JSObjectUnsafeExtension(this).values.cast<V>();
+
+  /// Creates a new Dart map with the same contents as this record.
+  Map<String, V> get toDart => {for (var (key, value) in pairs) key: value};
+
+  /// Creates a new, empty record.
+  factory JSRecord() => JSRecord._(JSObject());
+
+  /// Creates a [JSRecord] with the same keys and values as [other].
+  static JSRecord<V> ofRecord<V extends JSAny?>(JSRecord<V> other) =>
+      JSRecord<V>()..addAllRecord(other);
+
+  /// Like [Map.of], but creates a record.
+  static JSRecord<V> ofMap<V extends JSAny?>(Map<String, V> other) =>
+      JSRecord.fromEntries<V>(other.entries);
+
+  /// Like [Map.fromEntries], but creates a record.
+  static JSRecord<V> fromEntries<V extends JSAny?>(
+    Iterable<MapEntry<String, V>> entries,
+  ) => JSRecord<V>()..addEntries(entries);
+
+  /// Creates a new record and adds all the [pairs].
+  ///
+  /// If multiple pairs have the same key, later occurrences overwrite the value
+  /// of the earlier ones.
+  static JSRecord<V> fromPairs<V extends JSAny?>(Iterable<(String, V)> pairs) =>
+      JSRecord<V>()..addPairs(pairs);
+
+  /// See [Map.addAll].
+  void addAll(Map<String, V> other) => addEntries(other.entries);
+
+  /// Adds all enumerable, own, string key/value pairs of [other] to this
+  /// record.
+  ///
+  /// If a key of [other] is already in this record, its value is overwritten.
+  ///
+  /// The operation is equivalent to doing `this[key] = value` for each key and
+  /// associated value in [other]. It iterates over [other], which must therefore
+  /// not change during the iteration.
+  void addAllRecord(JSRecord<V> other) => addPairs(other.pairs);
+
+  /// See [Map.addEntries].
+  void addEntries(Iterable<MapEntry<String, V>> entries) {
+    for (var MapEntry(key: key, value: value) in entries) {
+      this[key] = value;
+    }
+  }
+
+  /// Adds all key/value pairs of [newPairs] to this record.
+  ///
+  /// If a key of [newPairs] is already in this record, the corresponding value
+  /// is overwritten.
+  ///
+  /// The operation is equivalent to doing `this[entry.key] = entry.value` for
+  /// each pair of the iterable.
+  void addPairs(Iterable<(String, V)> newPairs) {
+    for (var (key, value) in newPairs) {
+      this[key] = value;
+    }
+  }
+
+  /// See [Map.clear].
+  void clear() {
+    for (var key in JSObjectUnsafeExtension(this).keys) {
+      delete(key);
+    }
+  }
+
+  /// See [Map.containsKey].
+  bool containsKey(Object? key) =>
+      key is String && propertyIsEnumerable(key.toJS);
+
+  /// See [Map.containsValue].
+  bool containsValue(Object? value) => values.any((actual) => actual == value);
+
+  /// See [Map.forEach].
+  void forEach(void action(String key, V value)) {
+    for (var (key, value) in pairs) {
+      action(key, value);
+    }
+  }
+
+  /// See [Map.map].
+  Map<K2, V2> map<K2, V2>(MapEntry<K2, V2> convert(String key, V value)) =>
+      Map.fromEntries(pairs.map((pair) => convert(pair.$1, pair.$2)));
+
+  /// See [Map.putIfAbsent].
+  V putIfAbsent(String key, V ifAbsent()) {
+    if (containsKey(key)) return this[key]!;
+    var result = ifAbsent();
+    this[key] = result;
+    return result;
+  }
+
+  /// See [Map.remove].
+  V? remove(Object? key) {
+    if (!containsKey(key)) return null;
+    var value = this[key];
+    delete((key as String).toJS);
+    return value;
+  }
+
+  /// See [Map.removeWhere].
+  void removeWhere(bool test(String key, V value)) {
+    for (var (key, value) in pairs) {
+      if (test(key, value)) delete(key.toJS);
+    }
+  }
+
+  /// See [Map.update].
+  V update(String key, V update(V value), {V ifAbsent()?}) {
+    if (containsKey(key)) {
+      return this[key] = update(this[key]!);
+    } else if (ifAbsent == null) {
+      throw new ArgumentError("ifAbsent must be passed if the key is absent.");
+    } else {
+      return this[key] = ifAbsent();
+    }
+  }
+
+  /// See [Map.updateAll].
+  void updateAll(V update(String key, V value)) {
+    for (var (key, value) in pairs) {
+      this[key] = update(key, value);
+    }
+  }
+
+  /// See [Map.operator[]].
+  V? operator [](Object? key) =>
+      key is String ? getProperty(key.toJS) as V? : null;
+
+  /// See [Map.operator[]=].
+  void operator []=(String key, V value) => setProperty(key.toJS, value);
+}

js_interop/lib/src/unsafe/object.dart

@@ -0,0 +1,134 @@
+// Copyright (c) 2025, 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.
+
+import 'dart:js_interop';
+
+@JS('Object.assign')
+external void _assign(
+  JSObject target, [
+  JSAny? source1,
+  JSAny? source2,
+  JSAny? source3,
+  JSAny? source4,
+]);
+
+@JS('Object.entries')
+external JSArray<JSArray<JSAny?>> _entries(JSObject object);
+
+@JS('Object.freeze')
+external void _freeze(JSObject object);
+
+@JS('Reflect.get')
+external JSAny? _get(JSObject object, JSAny name, JSAny? thisArg);
+
+@JS('Object.getOwnPropertyNames')
+external JSArray<JSString> _getOwnPropertyNames(JSObject object);
+
+@JS('Object.getOwnPropertySymbols')
+external JSArray<JSSymbol> _getOwnPropertySymbols(JSObject object);
+
+@JS('Object.hasOwn')
+external bool _hasOwn(JSObject object, JSAny property);
+
+@JS('Object.keys')
+external JSArray<JSString> _keys(JSObject object);
+
+@JS('Reflect.ownKeys')
+external JSArray<JSAny> _ownKeys(JSObject object);
+
+@JS('Reflect.set')
+external bool _set(JSObject object, JSAny name, JSAny? value, JSAny? thisArg);
+
+@JS('Object.values')
+external JSArray<JSAny?> _values(JSObject object);
+
+/// Additional instance methods for the `dart:js_interop` [interop.JSObject]
+/// type meant to be used when the names of properties or methods are not known
+/// statically.
+extension JSObjectUnsafeExtension on JSObject {
+  /// See [`Object.entries()`].
+  ///
+  /// [`Object.entries()`]: https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/Object/entries
+  List<(String, JSAny?)> get entries => [
+    for (var entry in _entries(this).toDart)
+      ((entry[0] as JSString).toDart, entry[1]),
+  ];
+
+  /// See [`Reflect.ownKeys()`].
+  ///
+  /// The return value contains only [JSString]s and [JSSymbol]s.
+  ///
+  /// [`Reflect.ownKeys()`]: https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/Object/ownKeys
+  List<JSAny> get ownKeys => _ownKeys(this).toDart;
+
+  /// See [`Object.getOwnPropertyNames()`].
+  ///
+  /// [`Object.getOwnPropertyNames()`]: https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/Object/getOwnPropertyNames
+  List<JSString> get ownPropertyNames => _getOwnPropertyNames(this).toDart;
+
+  /// See [`Object.getOwnPropertySymbols()`].
+  ///
+  /// [`Object.getOwnPropertySymbols()`]: https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/Object/getOwnPropertySymbols
+  List<JSSymbol> get ownPropertySymbols => _getOwnPropertySymbols(this).toDart;
+
+  /// See [`Object.keys()`].
+  ///
+  /// [`Object.keys()`]: https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/Object/keys
+  List<JSString> get keys => _keys(this).toDart;
+
+  /// See [`Object.values()`].
+  ///
+  /// [`Object.values()`]: https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/Object/values
+  List<JSAny?> get values => _values(this).toDart;
+
+  /// See [`Object.assign()`].
+  ///
+  /// [`Object.assign()`]: https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/Object/assign
+  void assign([
+    JSObject? source1,
+    JSObject? source2,
+    JSObject? source3,
+    JSObject? source4,
+  ]) => _assign(this, source1, source2, source3, source4);
+
+  /// See [`Object.freeze()`].
+  ///
+  /// [`Object.freeze()`]: https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/Object/freeze
+  void freeze() => _freeze(this);
+
+  /// See [`Reflect.get()`].
+  ///
+  /// The [name] must be a [JSString] or a [JSSymbol].
+  ///
+  /// [`Reflect.get()`]: https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/Reflect/get
+  R getPropertyWithThis<R extends JSAny?>(JSAny name, JSAny? thisArg) =>
+      _get(this, name, thisArg) as R;
+
+  /// See [`Object.hasOwn()`].
+  ///
+  /// The [name] must be a [JSString] or a [JSSymbol].
+  ///
+  /// [`Object.hasOwn()`]: https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/Object/hasOwn
+  bool hasOwnProperty(JSAny name) => _hasOwn(this, name);
+
+  /// See [`Reflect.set()`].
+  ///
+  /// The [name] must be a [JSString] or a [JSSymbol].
+  ///
+  /// [`Reflect.set()`]: https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/Reflect/set
+  bool setPropertyWithThis(JSAny name, JSAny? thisArg, JSAny? value) =>
+      _set(this, name, value, thisArg);
+
+  /// See [`Object.isPrototypeOf()`].
+  ///
+  /// [`Object.isPrototypeOf()`]: https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/Object/isPrototypeOf
+  external bool isPrototypeOf(JSObject other);
+
+  /// See [`Object.propertyIsEnumerable()`].
+  ///
+  /// The [name] must be a [JSString] or a [JSSymbol].
+  ///
+  /// [`Object.propertyIsEnumerable()`]: https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/Object/propertyIsEnumerable
+  external bool propertyIsEnumerable(JSAny name);
+}

js_interop/lib/unsafe.dart

@@ -0,0 +1,12 @@
+// Copyright (c) 2025, 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.
+
+/// Like `dart:js_interop_unsafe`, this library contains utilities that treat JS
+/// objects as arbitrary sets of properties as well as those that expose JS's
+/// runtime reflection capabilities. It should be used with care as it can
+/// invalidate assumptions made by the statically type-annotated JS APIs used
+/// elsewhere.
+library;
+
+export 'src/unsafe/object.dart';