Use extension types and generics internally (#184)

Migrate @staticInterop to extension types, which enables us
to use generic arguments to JSArray and JSPromise.

Author: srujzs

tool/generator/filesystem_api.dart

@@ -2,31 +2,25 @@
 // 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.
 
+// TODO(srujzs): Remove this workaround once we use an SDK version that contains
+// https://github.com/dart-lang/sdk/issues/54801.
+@JS()
+library;
+
 import 'dart:js_interop';
 
 @JS()
 external FileSystem get fs;
 
-@JS()
-@anonymous
-@staticInterop
-class JSMkdirOptions {
+extension type JSMkdirOptions._(JSObject _) implements JSObject {
   external factory JSMkdirOptions({JSBoolean? recursive});
 }
 
-@JS()
-@anonymous
-@staticInterop
-class JSReadFileOptions {
+extension type JSReadFileOptions._(JSObject _) implements JSObject {
   external factory JSReadFileOptions({JSString? encoding});
 }
 
-@JS()
-@staticInterop
-class FileSystem {}
-
-// TODO(joshualitt): Replace `void` with `JSVoid`
-extension FileSystemExtension on FileSystem {
+extension type FileSystem._(JSObject _) implements JSObject {
   external JSBoolean existsSync(JSString path);
 
   @JS('mkdirSync')

tool/generator/generate_bindings.dart

@@ -6,20 +6,21 @@ import 'dart:js_interop';
 
 import 'translator.dart';
 import 'util.dart';
+import 'webidl_api.dart' as webidl;
 import 'webref_css_api.dart';
 import 'webref_idl_api.dart';
 
 /// Generate CSS property names for setting / getting CSS properties in JS.
 Future<List<String>> _generateCSSStyleDeclarations() async {
   final cssStyleDeclarations = <String>{};
-  final array = objectEntries(await css.listAll().toDart as JSObject);
+  final array = objectEntries(await css.listAll().toDart);
   for (var i = 0; i < array.length; i++) {
-    final entry = array[i] as JSArray;
-    final data = entry[1] as CSSEntries;
+    final entry = array[i] as JSArray<CSSEntries>;
+    final data = entry[1];
     final properties = data.properties;
     if (properties != null) {
       for (var j = 0; j < properties.length; j++) {
-        final property = properties[j] as CSSEntry;
+        final property = properties[j];
         // There are three cases for [styleDeclaration]:
         //   1) Length == 1, a single word CSS property.
         //   2) Length == 2, a kebab case property + a camel case property.
@@ -32,7 +33,7 @@ Future<List<String>> _generateCSSStyleDeclarations() async {
           }
           // For now we ignore browser specific properties.
           if (length == 3) continue;
-          final style = (styleDeclaration[length - 1] as JSString).toDart;
+          final style = styleDeclaration[length - 1].toDart;
           if (style.contains('-')) {
             throw Exception('Unexpected style declaration $styleDeclaration');
           }
@@ -49,11 +50,11 @@ Future<TranslationResult> generateBindings(
   final cssStyleDeclarations = await _generateCSSStyleDeclarations();
   final translator =
       Translator(packageRoot, librarySubDir, cssStyleDeclarations);
-  final array = objectEntries(await idl.parseAll().toDart as JSObject);
+  final array = objectEntries(await idl.parseAll().toDart);
   for (var i = 0; i < array.length; i++) {
-    final entry = array[i] as JSArray;
+    final entry = array[i] as JSArray<JSAny?>;
     final shortname = (entry[0] as JSString).toDart;
-    final ast = entry[1] as JSArray;
+    final ast = entry[1] as JSArray<webidl.Node>;
     translator.collect(shortname, ast);
   }
   translator.setOrUpdateInterfacelikes();

tool/generator/translator.dart

@@ -287,21 +287,21 @@ class _Parameter {
 class _OverridableMember {
   final List<_Parameter> parameters = [];
 
-  _OverridableMember(JSArray rawParameters) {
+  _OverridableMember(JSArray<idl.Argument> rawParameters) {
     for (var i = 0; i < rawParameters.length; i++) {
-      parameters.add(_Parameter(rawParameters[i] as idl.Argument));
+      parameters.add(_Parameter(rawParameters[i]));
     }
   }
 
-  void _processParameters(JSArray thoseParameters) {
+  void _processParameters(JSArray<idl.Argument> thoseParameters) {
     // Assume if we have extra arguments beyond what was provided in some other
     // method, that these are all optional.
     final thatLength = thoseParameters.length;
     for (var i = thatLength; i < parameters.length; i++) {
       parameters[i].isOptional = true;
     }
     for (var i = 0; i < thatLength; i++) {
-      final argument = thoseParameters[i] as idl.Argument;
+      final argument = thoseParameters[i];
       if (i >= parameters.length) {
         // We assume these parameters must be optional, regardless of what the
         // IDL says.
@@ -361,9 +361,9 @@ class _PartialInterfacelike {
     return partialInterfacelike;
   }
 
-  void _processMembers(JSArray nodeMembers) {
+  void _processMembers(JSArray<idl.Member> nodeMembers) {
     for (var i = 0; i < nodeMembers.length; i++) {
-      final member = nodeMembers[i] as idl.Member;
+      final member = nodeMembers[i];
       final type = member.type;
       switch (type) {
         case 'constructor':
@@ -532,14 +532,14 @@ class Translator {
     }
   }
 
-  void collect(String shortName, JSArray ast) {
+  void collect(String shortName, JSArray<idl.Node> ast) {
     final libraryPath = '$_librarySubDir/${shortName.kebabToSnake}.dart';
     assert(!_libraries.containsKey(libraryPath));
 
     final library = _Library(this, '$packageRoot/$libraryPath');
 
     for (var i = 0; i < ast.length; i++) {
-      library.add(ast[i] as idl.Node);
+      library.add(ast[i]);
     }
 
     if (_shouldGenerate(shortName, library)) {

tool/generator/util.dart

@@ -8,10 +8,11 @@ import 'filesystem_api.dart';
 
 // TODO(joshualitt): Let's find a better place for these.
 @JS('Object.entries')
-external JSArray objectEntries(JSObject o);
+external JSArray<JSAny?> objectEntries(JSObject o);
 
-extension JSArrayExtension on JSArray {
-  external JSAny? operator [](int i);
+// TODO(srujzs): Remove once this is in dart:js_interop.
+extension JSArrayExtension<T extends JSAny?> on JSArray<T> {
+  external T operator [](int i);
   external int get length;
 }
 

tool/generator/webidl_api.dart

@@ -4,11 +4,7 @@
 
 import 'dart:js_interop';
 
-@JS()
-@staticInterop
-class IDLType {}
-
-extension IDLTypeExtension on IDLType {
+extension type IDLType._(JSObject _) implements JSObject {
   external String? get type;
   external String get generic;
   external JSAny get idlType;
@@ -18,21 +14,13 @@ extension IDLTypeExtension on IDLType {
 
 /// The abstract node interface in the IDL AST. All nodes that can occur at the
 /// root of the IDL inherit from [Node].
-@JS()
-@staticInterop
-class Node {}
-
-extension NodeExtension on Node {
+extension type Node._(JSObject _) implements JSObject {
   external String get type;
 }
 
 /// The abstract node interface for named nodes in the IDL. Most root nodes have
 /// names, with the exception of `includes`.
-@JS()
-@staticInterop
-class Named extends Node {}
-
-extension NamedExtension on Named {
+extension type Named._(JSObject _) implements Node {
   external String get name;
 }
 
@@ -43,69 +31,39 @@ extension NamedExtension on Named {
 ///   * callback interface
 ///   * dictionary
 /// To disambiguate, use the `type` getter.
-@JS()
-@staticInterop
-class Interfacelike extends Named {}
-
-extension InterfaceExtension on Interfacelike {
+extension type Interfacelike._(JSObject _) implements Named {
   external bool get partial;
-  external JSArray get members;
+  external JSArray<Member> get members;
   external String? get inheritance;
 }
 
-@JS()
-@staticInterop
-class Callback extends Named {}
-
-extension CallbackExtension on Callback {
+extension type Callback._(JSObject _) implements Named {
   external IDLType get idlType;
-  external JSArray get arguments;
+  external JSArray<Argument> get arguments;
 }
 
-@JS()
-@staticInterop
-class EnumValue {}
-
-extension EnumValueExtension on EnumValue {
+extension type EnumValue._(JSObject _) implements JSObject {
   external String get type;
   external String get value;
 }
 
-@JS()
-@staticInterop
-class Enum extends Named {}
-
-@JS()
-@staticInterop
-class Typedef extends Named {}
+extension type Enum._(JSObject _) implements Named {}
 
-extension TypedefExtension on Typedef {
+extension type Typedef._(JSObject _) implements Named {
   external IDLType get idlType;
 }
 
-@JS()
-@staticInterop
-class Includes extends Node {}
-
-extension IncludesExtension on Includes {
+extension type Includes._(JSObject _) implements Node {
   external String get target;
   external String get includes;
 }
 
 /// All members inherit from the [Member] node.
-@JS()
-@staticInterop
-class Member {}
-
-extension MemberExtension on Member {
+extension type Member._(JSObject _) implements JSObject {
   external String get type;
 }
 
-@JS()
-@staticInterop
-class Argument {}
-
-extension ArgumentExtension on Argument {
+extension type Argument._(JSObject _) implements JSObject {
   external String get type;
   @JS('default')
   external Value? get defaultValue;
@@ -115,63 +73,39 @@ extension ArgumentExtension on Argument {
   external String get name;
 }
 
-@JS()
-@staticInterop
-class Operation extends Member {}
-
-extension OperationExtension on Operation {
+extension type Operation._(JSObject _) implements Member {
   external String get special;
   external IDLType get idlType;
   external String get name;
-  external JSArray get arguments;
+  external JSArray<Argument> get arguments;
 }
 
-@JS()
-@staticInterop
-class Constructor extends Member {}
-
-extension ConstructorExtension on Constructor {
-  external JSArray get arguments;
+extension type Constructor._(JSObject _) implements Member {
+  external JSArray<Argument> get arguments;
 }
 
-@JS()
-@staticInterop
-class Attribute extends Member {}
-
-extension AttributeExtension on Attribute {
+extension type Attribute._(JSObject _) implements Member {
   external String get special;
   external bool get readonly;
   external IDLType get idlType;
   external String get name;
 }
 
-@JS()
-@staticInterop
-class Field extends Member {}
-
-extension FieldExtension on Field {
+extension type Field._(JSObject _) implements Member {
   external String get name;
   external bool get required;
   external IDLType get idlType;
   @JS('default')
   external Value? get defaultValue;
 }
 
-@JS()
-@staticInterop
-class Value {}
-
-extension ValueExtension on Value {
+extension type Value._(JSObject _) implements JSObject {
   external String get type;
   external JSAny? get value;
   external bool? get negative;
 }
 
-@JS()
-@staticInterop
-class Constant extends Member {}
-
-extension ConstantExtension on Constant {
+extension type Constant._(JSObject _) implements Member {
   external IDLType get idlType;
   external String get name;
   external Value get value;
@@ -182,23 +116,15 @@ extension ConstantExtension on Constant {
 ///   * async iterable<>
 ///   * maplike<>
 ///   * setlike<>
-@JS()
-@staticInterop
-class MemberDeclaration {}
-
-extension MemberDeclarationExtension on MemberDeclaration {
+extension type MemberDeclaration._(JSObject _) implements JSObject {
   external String get type;
   external IDLType get idlType;
   external bool get readonly;
   external bool get async;
-  external JSArray get arguments;
+  external JSArray<Argument> get arguments;
 }
 
-@JS()
-@staticInterop
-class EOF {}
-
-extension EOFExtension on EOF {
+extension type EOF._(JSObject _) implements JSObject {
   external String get type;
   external String get value;
 }