[dart:js_interop] Add/fix some js_interop helpers

Minus all the operator-related functionalities, members that
can be worked around using static interop e.g. getPrototypeOf,
and createDartExport/createStaticInteropMock, this bridges the
gap of js_util.

Adds:
- instanceOfString from js_util as an extension methods
- JSObject constructor to replace js_util.newObject
- Unnamed factory constructor to JSAny so users can't extend it

Fixes:
- JSArray.withLength to take an int
- typeofEquals to take a String and return a bool
- instanceof to return a bool

CoreLibraryReviewExempt: Backend-specific library.
Change-Id: I7db1651f641a4fc84392957dfa7ad64904f110e8
Reviewed-on: https://dart-review.googlesource.com/c/sdk/+/326691
Reviewed-by: Sigmund Cherem <sigmund@google.com>
Commit-Queue: Srujan Gaddam <srujzs@google.com>

CHANGELOG.md

@@ -167,6 +167,14 @@ constraint][language version] lower bound to 3.2 or greater (`sdk: '^3.2.0'`).
   conflates the two values and treats them both as Dart null. Therefore, these
   two helper methods should not be used on dart2wasm and will throw to avoid
   potentially erroneous code.
+- **Breaking Change on `dart:js_interop` `typeofEquals` and `instanceof`**:
+  Both APIs now return a `bool` instead of a `JSBoolean`. `typeofEquals` also
+  now takes in a `String` instead of a `JSString`.
+- **Breaking Change on `dart:js_interop` `JSAny` and `JSObject`**:
+  These types can only be implemented, and no longer extended, by user
+  `@staticInterop` types.
+- **Breaking Change on `dart:js_interop` `JSArray.withLength`**:
+  This API now takes in an `int` instead of `JSNumber`.
 
 ### Tools
 

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

@@ -997,3 +997,6 @@ external Object jsObjectSetPrototypeOf(@notNull Object obj, Object? prototype);
 /// inline the call so this will be an extra level of indirection. DDC manually
 /// inlines this method in the compiler instead.
 external Object get staticInteropGlobalContext;
+
+/// Return a fresh object literal.
+T createObjectLiteral<T>() => JS('PlainJavaScriptObject', '{}');

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

@@ -3376,3 +3376,6 @@ abstract class TrustedGetRuntimeType {}
 /// This should match the global context that non-static interop members use.
 Object get staticInteropGlobalContext =>
     JS('creates:;returns:Object;depends:none;effects:none;gvn:true', 'self');
+
+/// Return a fresh object literal.
+T createObjectLiteral<T>() => JS('PlainJavaScriptObject', '{}');

sdk/lib/_internal/js_shared/lib/js_interop_patch.dart

@@ -19,7 +19,7 @@ JSObject get globalContext => staticInteropGlobalContext as JSObject;
 extension NullableUndefineableJSAnyExtension on JSAny? {
   @patch
   @pragma('dart2js:prefer-inline')
-  bool get isUndefined => js_util.typeofEquals(this, 'undefined');
+  bool get isUndefined => typeofEquals('undefined');
 
   @patch
   @pragma('dart2js:prefer-inline')
@@ -27,7 +27,7 @@ extension NullableUndefineableJSAnyExtension on JSAny? {
 
   @patch
   @pragma('dart2js:prefer-inline')
-  JSBoolean typeofEquals(JSString typeString) =>
+  bool typeofEquals(String typeString) =>
       foreign_helper.JS('bool', 'typeof # === #', this, typeString);
 
   @patch
@@ -48,7 +48,7 @@ extension NullableObjectUtilExtension on Object? {
 extension JSObjectUtilExtension on JSObject {
   @patch
   @pragma('dart2js:prefer-inline')
-  JSBoolean instanceof(JSFunction constructor) =>
+  bool instanceof(JSFunction constructor) =>
       foreign_helper.JS('bool', '# instanceof #', this, constructor);
 }
 

sdk/lib/_internal/js_shared/lib/js_types.dart

@@ -30,14 +30,21 @@
 library _js_types;
 
 import 'dart:_js_annotations';
+import 'dart:_js_helper' show createObjectLiteral;
 
 @JS()
 @staticInterop
-class JSAny {}
+class JSAny {
+  // Unnamed factory constructor so users can only implement JSAny.
+  external factory JSAny._();
+}
 
 @JS()
 @staticInterop
-class JSObject implements JSAny {}
+class JSObject implements JSAny {
+  /// Returns a new object literal.
+  factory JSObject() => createObjectLiteral<JSObject>();
+}
 
 @JS()
 @staticInterop
@@ -51,8 +58,7 @@ class JSExportedDartFunction implements JSFunction {}
 @staticInterop
 class JSArray implements JSObject {
   external factory JSArray();
-  // TODO(srujzs): Should we make this an `int`?
-  external factory JSArray.withLength(JSNumber length);
+  external factory JSArray.withLength(int length);
 }
 
 @JS()

sdk/lib/_internal/js_shared/lib/js_util_patch.dart

@@ -5,7 +5,11 @@
 import 'dart:_foreign_helper' show JS;
 import 'dart:_internal' show patch;
 import 'dart:_js_helper'
-    show convertDartClosureToJS, assertInterop, assertInteropArgs;
+    show
+        assertInterop,
+        assertInteropArgs,
+        convertDartClosureToJS,
+        createObjectLiteral;
 import 'dart:collection' show HashMap;
 import 'dart:async' show Completer;
 import 'dart:typed_data';
@@ -67,7 +71,7 @@ dynamic jsify(Object? object) {
 Object get globalThis => JS('', 'globalThis');
 
 @patch
-T newObject<T>() => JS('PlainJavaScriptObject', '{}');
+T newObject<T>() => createObjectLiteral<T>();
 
 @patch
 bool hasProperty(Object o, Object name) => JS('bool', '# in #', name, o);

sdk/lib/_internal/wasm/lib/js_helper.dart

@@ -523,7 +523,7 @@ List<int> jsIntTypedArrayToDartIntTypedData(
 
 JSArray toJSArray(List<JSAny?> list) {
   int length = list.length;
-  JSArray result = JSArray.withLength(length.toJS);
+  JSArray result = JSArray.withLength(length);
   for (int i = 0; i < length; i++) {
     result[i.toJS] = list[i];
   }

sdk/lib/_internal/wasm/lib/js_interop_patch.dart

@@ -41,9 +41,10 @@ extension NullableUndefineableJSAnyExtension on JSAny? {
           "this API should not be used when compiling to Wasm.");
 
   @patch
-  JSBoolean typeofEquals(JSString type) =>
-      _box<JSBoolean>(js_helper.JS<WasmExternRef?>(
-          '(o, t) => typeof o === t', this?.toExternRef, type.toExternRef));
+  bool typeofEquals(String type) =>
+      _box<JSBoolean>(js_helper.JS<WasmExternRef?>('(o, t) => typeof o === t',
+              this?.toExternRef, type.toJS.toExternRef))
+          .toDart;
 
   @patch
   Object? dartify() => js_util.dartify(this);
@@ -60,9 +61,10 @@ extension NullableObjectUtilExtension on Object? {
 @patch
 extension JSObjectUtilExtension on JSObject {
   @patch
-  JSBoolean instanceof(JSFunction constructor) =>
+  bool instanceof(JSFunction constructor) =>
       _box<JSBoolean>(js_helper.JS<WasmExternRef?>(
-          '(o, c) => o instanceof c', toExternRef, constructor.toExternRef));
+              '(o, c) => o instanceof c', toExternRef, constructor.toExternRef))
+          .toDart;
 }
 
 /// [JSExportedDartFunction] <-> [Function]

sdk/lib/_internal/wasm/lib/js_types.dart

@@ -77,11 +77,17 @@ part 'js_typed_array.dart';
 ///    JS and Wasm backends until we have a better story here.
 @JS()
 @staticInterop
-class JSAny {}
+class JSAny {
+  // Unnamed factory constructor so users can only implement JSAny.
+  external factory JSAny._();
+}
 
 @JS()
 @staticInterop
-class JSObject implements JSAny {}
+class JSObject implements JSAny {
+  /// Returns a new object literal.
+  factory JSObject() => js.JSValue(js.newObjectRaw()) as JSObject;
+}
 
 @JS()
 @staticInterop
@@ -101,8 +107,7 @@ class JSPromise implements JSObject {
 @staticInterop
 class JSArray implements JSObject {
   external factory JSArray();
-  // TODO(srujzs): Should we make this an `int`?
-  external factory JSArray.withLength(JSNumber length);
+  external factory JSArray.withLength(int length);
 }
 
 @JS()

sdk/lib/js_interop/js_interop.dart

@@ -178,7 +178,7 @@ extension NullableUndefineableJSAnyExtension on JSAny? {
 
   bool get isUndefinedOrNull => this == null;
   bool get isDefinedAndNotNull => !isUndefinedOrNull;
-  external JSBoolean typeofEquals(JSString typeString);
+  external bool typeofEquals(String typeString);
 
   /// Effectively the inverse of [jsify], [dartify] Takes a JavaScript object,
   /// and converts it to a Dart based object. Only JS primitives, arrays, or
@@ -195,7 +195,14 @@ extension NullableObjectUtilExtension on Object? {
 
 /// Utility extensions for [JSObject].
 extension JSObjectUtilExtension on JSObject {
-  external JSBoolean instanceof(JSFunction constructor);
+  external bool instanceof(JSFunction constructor);
+
+  /// Like [instanceof], but only takes a [String] for the constructor name,
+  /// which is then looked up in the [globalContext].
+  bool instanceOfString(String constructorName) {
+    final constructor = globalContext[constructorName] as JSFunction?;
+    return constructor != null && instanceof(constructor);
+  }
 }
 
 /// The type of `JSUndefined` when returned from functions. Unlike pure JS,

tests/lib/js/static_interop_test/js_types_test.dart

@@ -309,7 +309,7 @@ void syncTests() {
   expect(nullAny, null);
   expect(nullAny.isUndefinedOrNull, true);
   expect(nullAny.isDefinedAndNotNull, false);
-  expect(typeofEquals(nullAny, 'object'), true);
+  expect(nullAny.typeofEquals('object'), true);
   if (isJSBackend) {
     expect(undefinedAny.isNull, false);
     expect(undefinedAny.isUndefined, true);
@@ -317,15 +317,15 @@ void syncTests() {
   expect(undefinedAny.isUndefinedOrNull, true);
   expect(undefinedAny.isDefinedAndNotNull, false);
   if (isJSBackend) {
-    expect(typeofEquals(undefinedAny, 'undefined'), true);
+    expect(undefinedAny.typeofEquals('undefined'), true);
     expect(definedNonNullAny.isNull, false);
     expect(definedNonNullAny.isUndefined, false);
   } else {
-    expect(typeofEquals(undefinedAny, 'object'), true);
+    expect(undefinedAny.typeofEquals('object'), true);
   }
   expect(definedNonNullAny.isUndefinedOrNull, false);
   expect(definedNonNullAny.isDefinedAndNotNull, true);
-  expect(typeofEquals(definedNonNullAny, 'object'), true);
+  expect(definedNonNullAny.typeofEquals('object'), true);
 }
 
 @JS()
@@ -436,8 +436,7 @@ Future<void> asyncTests() async {
     } catch (e) {
       expect(e is JSObject, true);
       final jsError = e as JSObject;
-      expect(jsError.instanceof(globalContext['Error'] as JSFunction).toDart,
-          true);
+      expect(jsError.instanceof(globalContext['Error'] as JSFunction), true);
       expect((jsError['error'] as JSBoxedDartObject).toDart is Exception, true);
       StackTrace.fromString((jsError['stack'] as JSString).toDart);
     }
@@ -462,8 +461,7 @@ Future<void> asyncTests() async {
     } catch (e) {
       expect(e is JSObject, true);
       final jsError = e as JSObject;
-      expect(jsError.instanceof(globalContext['Error'] as JSFunction).toDart,
-          true);
+      expect(jsError.instanceof(globalContext['Error'] as JSFunction), true);
       expect((jsError['error'] as JSBoxedDartObject).toDart is Exception, true);
       StackTrace.fromString((jsError['stack'] as JSString).toDart);
     }

tests/lib/js/static_interop_test/subtype_js_types_static_test.dart

@@ -10,6 +10,10 @@ import 'dart:js_interop';
 @JS()
 @staticInterop
 class ExtendsJSAny extends JSAny {}
+//    ^
+// [web] The superclass, 'JSAny', has no unnamed constructor that takes no arguments.
+//                         ^^^^^
+// [analyzer] COMPILE_TIME_ERROR.NO_GENERATIVE_CONSTRUCTORS_IN_SUPERCLASS
 
 @JS()
 @staticInterop
@@ -18,6 +22,10 @@ class ImplementsJSAny implements JSAny {}
 @JS()
 @staticInterop
 class ExtendsJSObject extends JSObject {}
+//    ^
+// [web] The superclass, 'JSObject', has no unnamed constructor that takes no arguments.
+//                            ^^^^^^^^
+// [analyzer] COMPILE_TIME_ERROR.NO_GENERATIVE_CONSTRUCTORS_IN_SUPERCLASS
 
 @JS()
 @staticInterop

tests/lib/js_interop_unsafe/basic_test.dart

@@ -4,9 +4,6 @@
 
 import 'dart:js_interop';
 import 'dart:js_interop_unsafe';
-// TODO(joshualitt): Once we reify JS types on JS backends, we can add a
-// constructor to [JSObject].
-import 'dart:js_util' show newObject;
 import 'dart:typed_data';
 
 import 'package:expect/expect.dart';
@@ -15,7 +12,7 @@ import 'package:expect/expect.dart';
 external void eval(String code);
 
 void createObjectTest() {
-  JSObject o = newObject<JSObject>();
+  JSObject o = JSObject();
   Expect.isFalse(o.hasProperty('foo'.toJS).toDart);
   o['foo'] = 'bar'.toJS;
   Expect.isTrue(o.hasProperty('foo'.toJS).toDart);
@@ -25,8 +22,8 @@ void createObjectTest() {
 void equalTest() {
   // Different objects aren't equal.
   {
-    JSObject o1 = newObject<JSObject>();
-    JSObject o2 = newObject<JSObject>();
+    JSObject o1 = JSObject();
+    JSObject o2 = JSObject();
     Expect.notEquals(o1, o2);
   }
 
@@ -82,11 +79,10 @@ void typeofTest() {
     'symbol'
   };
   void test(String property, String expectedType) {
-    Expect.isTrue(
-        globalContext[property]?.typeofEquals(expectedType.toJS).toDart);
+    Expect.isTrue(globalContext[property]?.typeofEquals(expectedType));
     for (final type in types) {
       if (type != expectedType) {
-        Expect.isFalse(globalContext[property]?.typeofEquals(type.toJS).toDart);
+        Expect.isFalse(globalContext[property]?.typeofEquals(type));
       }
     }
   }
@@ -112,8 +108,10 @@ void instanceOfTest() {
   JSObject obj = gc['obj'] as JSObject;
   JSFunction jsClass1Constructor = gc['JSClass1'] as JSFunction;
   JSFunction jsClass2Constructor = gc['JSClass2'] as JSFunction;
-  Expect.isTrue(obj.instanceof(jsClass1Constructor).toDart);
-  Expect.isFalse(obj.instanceof(jsClass2Constructor).toDart);
+  Expect.isTrue(obj.instanceof(jsClass1Constructor));
+  Expect.isFalse(obj.instanceof(jsClass2Constructor));
+  Expect.isTrue(obj.instanceOfString('JSClass1'));
+  Expect.isFalse(obj.instanceOfString('JSClass2'));
 }
 
 void _expectIterableEquals(Iterable<Object?> l, Iterable<Object?> r) {

tests/lib_2/js/static_interop_test/subtype_js_types_static_test.dart

@@ -10,6 +10,10 @@ import 'dart:js_interop';
 @JS()
 @staticInterop
 class ExtendsJSAny extends JSAny {}
+//    ^
+// [web] The superclass, 'JSAny', has no unnamed constructor that takes no arguments.
+//                         ^^^^^
+// [analyzer] COMPILE_TIME_ERROR.NO_GENERATIVE_CONSTRUCTORS_IN_SUPERCLASS
 
 @JS()
 @staticInterop
@@ -18,6 +22,10 @@ class ImplementsJSAny implements JSAny {}
 @JS()
 @staticInterop
 class ExtendsJSObject extends JSObject {}
+//    ^
+// [web] The superclass, 'JSObject', has no unnamed constructor that takes no arguments.
+//                            ^^^^^^^^
+// [analyzer] COMPILE_TIME_ERROR.NO_GENERATIVE_CONSTRUCTORS_IN_SUPERCLASS
 
 @JS()
 @staticInterop