Add [] and []= operators for unnamed getters and setters (dart-lang#293)

Closes dart-lang#127

The IDL defines unnamed getters or setters which should be
emitted as special variants of the index operators.

web/CHANGELOG.md

@@ -5,6 +5,8 @@
   `dart:io` and `dart:html`.
 - Added `JSImmutableListWrapper` which helps create a dart list from a JS list.
 - Deprecated `TouchListWrapper` and `TouchListConvert` in favor of `JSImmutableListWrapper`.
+- Added `[]` and `[]=` overloaded operators to types which define unnamed
+  `getter`s and `setter`s, respectively.
 
 ## 1.0.0
 

web/lib/src/dom/css_animations.dart

@@ -106,6 +106,8 @@ extension type CSSKeyframeRule._(JSObject _) implements CSSRule, JSObject {
 /// API documentation sourced from
 /// [MDN Web Docs](https://developer.mozilla.org/en-US/docs/Web/API/CSSKeyframesRule).
 extension type CSSKeyframesRule._(JSObject _) implements CSSRule, JSObject {
+  external CSSKeyframeRule operator [](int index);
+
   /// The **`appendRule()`** method of the [CSSKeyframeRule] interface appends a
   /// [CSSKeyFrameRule] to the end of the rules.
   external void appendRule(String rule);

web/lib/src/dom/css_typed_om.dart

@@ -139,6 +139,12 @@ extension type CSSUnparsedValue._(JSObject _)
     implements CSSStyleValue, JSObject {
   external factory CSSUnparsedValue(JSArray<CSSUnparsedSegment> members);
 
+  external CSSUnparsedSegment operator [](int index);
+  external void operator []=(
+    int index,
+    CSSUnparsedSegment val,
+  );
+
   /// The **`length`** read-only property of the
   /// [CSSUnparsedValue] interface returns the number of items in the object.
   external int get length;
@@ -468,6 +474,8 @@ extension type CSSMathClamp._(JSObject _) implements CSSMathValue, JSObject {
 /// API documentation sourced from
 /// [MDN Web Docs](https://developer.mozilla.org/en-US/docs/Web/API/CSSNumericArray).
 extension type CSSNumericArray._(JSObject _) implements JSObject {
+  external CSSNumericValue operator [](int index);
+
   /// The read-only **`length`** property of the
   /// [CSSNumericArray] interface returns the number of
   /// [CSSNumericValue] objects in the list.
@@ -486,6 +494,12 @@ extension type CSSTransformValue._(JSObject _)
     implements CSSStyleValue, JSObject {
   external factory CSSTransformValue(JSArray<CSSTransformComponent> transforms);
 
+  external CSSTransformComponent operator [](int index);
+  external void operator []=(
+    int index,
+    CSSTransformComponent val,
+  );
+
   /// The **`toMatrix()`** method of the
   /// [CSSTransformValue] interface returns a [DOMMatrix] object.
   external DOMMatrix toMatrix();

web/lib/src/dom/dom.dart

@@ -1568,6 +1568,7 @@ extension type Document._(JSObject _) implements Node, JSObject {
   /// fullscreen mode, restoring the previous state of the screen. This usually
   /// reverses the effects of a previous call to [Element.requestFullscreen].
   external JSPromise<JSAny?> exitFullscreen();
+  external JSObject operator [](String name);
 
   /// The **`getElementsByName()`** method
   /// of the [Document] object returns a [NodeList] Collection of

web/lib/src/dom/html.dart

@@ -121,6 +121,8 @@ typedef WorkerType = String;
 /// API documentation sourced from
 /// [MDN Web Docs](https://developer.mozilla.org/en-US/docs/Web/API/HTMLAllCollection).
 extension type HTMLAllCollection._(JSObject _) implements JSObject {
+  external Element operator [](int index);
+
   /// The **`namedItem()`** method of the [HTMLAllCollection] interface returns
   /// the first [Element] in the collection whose `id` or `name` attribute
   /// matches the specified name, or `null` if no element matches.
@@ -197,6 +199,10 @@ extension type RadioNodeList._(JSObject _) implements NodeList, JSObject {
 /// [MDN Web Docs](https://developer.mozilla.org/en-US/docs/Web/API/HTMLOptionsCollection).
 extension type HTMLOptionsCollection._(JSObject _)
     implements HTMLCollection, JSObject {
+  external void operator []=(
+    int index,
+    HTMLOptionElement? option,
+  );
   external void add(
     JSObject element, [
     JSAny? before,
@@ -1271,7 +1277,13 @@ extension type HTMLUnknownElement._(JSObject _)
 ///
 /// API documentation sourced from
 /// [MDN Web Docs](https://developer.mozilla.org/en-US/docs/Web/API/DOMStringMap).
-extension type DOMStringMap._(JSObject _) implements JSObject {}
+extension type DOMStringMap._(JSObject _) implements JSObject {
+  external String operator [](String name);
+  external void operator []=(
+    String name,
+    String value,
+  );
+}
 
 /// The **`HTMLHtmlElement`** interface serves as the root node for a given HTML
 /// document. This object inherits the properties and methods described in the
@@ -3728,6 +3740,8 @@ extension type MediaError._(JSObject _) implements JSObject {
 /// API documentation sourced from
 /// [MDN Web Docs](https://developer.mozilla.org/en-US/docs/Web/API/AudioTrackList).
 extension type AudioTrackList._(JSObject _) implements EventTarget, JSObject {
+  external AudioTrack operator [](int index);
+
   /// The **[AudioTrackList]** method **`getTrackById()`** returns the first
   /// [AudioTrack] object from the track list whose [AudioTrack.id] matches the
   /// specified string.
@@ -3829,6 +3843,8 @@ extension type AudioTrack._(JSObject _) implements JSObject {
 /// API documentation sourced from
 /// [MDN Web Docs](https://developer.mozilla.org/en-US/docs/Web/API/VideoTrackList).
 extension type VideoTrackList._(JSObject _) implements EventTarget, JSObject {
+  external VideoTrack operator [](int index);
+
   /// The **[VideoTrackList]** method
   /// **`getTrackById()`** returns the first
   /// [VideoTrack] object from the track list whose [VideoTrack.id] matches the
@@ -3949,6 +3965,8 @@ extension type VideoTrack._(JSObject _) implements JSObject {
 /// API documentation sourced from
 /// [MDN Web Docs](https://developer.mozilla.org/en-US/docs/Web/API/TextTrackList).
 extension type TextTrackList._(JSObject _) implements EventTarget, JSObject {
+  external TextTrack operator [](int index);
+
   /// The **[TextTrackList]** method
   /// **`getTrackById()`** returns the first
   /// [TextTrack] object from the track list whose
@@ -4096,6 +4114,8 @@ extension type TextTrack._(JSObject _) implements EventTarget, JSObject {
 /// API documentation sourced from
 /// [MDN Web Docs](https://developer.mozilla.org/en-US/docs/Web/API/TextTrackCueList).
 extension type TextTrackCueList._(JSObject _) implements JSObject {
+  external TextTrackCue operator [](int index);
+
   /// The **`getCueById()`** method of the [TextTrackCueList] interface returns
   /// the first [VTTCue] in the list represented by the `TextTrackCueList`
   /// object whose identifier matches the value of `id`.
@@ -5045,6 +5065,8 @@ extension type HTMLFormElement._(JSObject _) implements HTMLElement, JSObject {
   /// Creates an [HTMLFormElement] using the tag 'form'.
   HTMLFormElement() : _ = document.createElement('form');
 
+  external JSObject operator [](JSAny indexOrName);
+
   /// The **`HTMLFormElement.submit()`** method submits a given
   /// `form`.
   ///
@@ -5900,6 +5922,10 @@ extension type HTMLSelectElement._(JSObject _)
   /// at the specified index from the options collection for this select
   /// element.
   external void remove([int index]);
+  external void operator []=(
+    int index,
+    HTMLOptionElement? option,
+  );
 
   /// The **`HTMLSelectElement.checkValidity()`** method checks
   /// whether the element has any constraints and whether it satisfies them. If
@@ -9823,6 +9849,8 @@ extension type DataTransfer._(JSObject _) implements JSObject {
 /// API documentation sourced from
 /// [MDN Web Docs](https://developer.mozilla.org/en-US/docs/Web/API/DataTransferItemList).
 extension type DataTransferItemList._(JSObject _) implements JSObject {
+  external DataTransferItem operator [](int index);
+
   /// The **`DataTransferItemList.add()`** method creates a new
   /// [DataTransferItem] using the specified data and adds it to the drag data
   /// list. The item may be a [File] or a string of a
@@ -10136,6 +10164,7 @@ extension type Window._(JSObject _) implements EventTarget, JSObject {
     String target,
     String features,
   ]);
+  external JSObject operator [](String name);
 
   /// `window.alert()` instructs the browser to display a dialog with an
   /// optional message, and to wait until the user dismisses the dialog.

web/lib/src/dom/media_source.dart

@@ -323,6 +323,8 @@ extension type SourceBuffer._(JSObject _) implements EventTarget, JSObject {
 /// API documentation sourced from
 /// [MDN Web Docs](https://developer.mozilla.org/en-US/docs/Web/API/SourceBufferList).
 extension type SourceBufferList._(JSObject _) implements EventTarget, JSObject {
+  external SourceBuffer operator [](int index);
+
   /// The **`length`** read-only property of the
   /// [SourceBufferList] interface returns the number of
   /// [SourceBuffer] objects in the list.

web/lib/src/dom/svg.dart

@@ -510,6 +510,10 @@ extension type SVGNumberList._(JSObject _) implements JSObject {
   );
   external SVGNumber removeItem(int index);
   external SVGNumber appendItem(SVGNumber newItem);
+  external void operator []=(
+    int index,
+    SVGNumber newItem,
+  );
   external int get length;
   external int get numberOfItems;
 }
@@ -534,6 +538,10 @@ extension type SVGLengthList._(JSObject _) implements JSObject {
   );
   external SVGLength removeItem(int index);
   external SVGLength appendItem(SVGLength newItem);
+  external void operator []=(
+    int index,
+    SVGLength newItem,
+  );
   external int get length;
   external int get numberOfItems;
 }
@@ -558,6 +566,10 @@ extension type SVGStringList._(JSObject _) implements JSObject {
   );
   external String removeItem(int index);
   external String appendItem(String newItem);
+  external void operator []=(
+    int index,
+    String newItem,
+  );
   external int get numberOfItems;
 }
 
@@ -1093,6 +1105,10 @@ extension type SVGTransformList._(JSObject _) implements JSObject {
   );
   external SVGTransform removeItem(int index);
   external SVGTransform appendItem(SVGTransform newItem);
+  external void operator []=(
+    int index,
+    SVGTransform newItem,
+  );
   external SVGTransform createSVGTransformFromMatrix([DOMMatrix2DInit matrix]);
   external SVGTransform? consolidate();
   external int get numberOfItems;
@@ -1317,6 +1333,10 @@ extension type SVGPointList._(JSObject _) implements JSObject {
   /// The **`appendItem()`** method of the [SVGPointList] interface adds a
   /// [SVGPoint] to the end of the list.
   external DOMPoint appendItem(DOMPoint newItem);
+  external void operator []=(
+    int index,
+    DOMPoint newItem,
+  );
 
   /// The **`length`** read-only property of the [SVGPointList] interface
   /// returns the number of items in the list.

web/test/smoke_test.dart

@@ -51,4 +51,15 @@ void main() {
     expect(div.style.textOverflow, equals('ellipsis'));
     expect(div.style.getPropertyValue('text-overflow'), equals('ellipsis'));
   });
+
+  test('External [] and []= operators work as expected.', () {
+    // []
+    expect(window['document'], window.document);
+    expect(window.document['body'], window.document.body);
+    // []=
+    final select = HTMLSelectElement();
+    final option = HTMLOptionElement();
+    select[0] = option;
+    expect(select.item(0), option);
+  });
 }

web_generator/lib/src/translator.dart

@@ -264,6 +264,10 @@ class _RawType {
     nullable = union.nullable;
     typeParameter = union.typeParameter;
   }
+
+  @override
+  String toString() => '_RawType(type: $type, nullable: $nullable, '
+      'typeParameter: $typeParameter)';
 }
 
 class _Parameter {
@@ -366,19 +370,21 @@ class _OverridableOperation extends _OverridableMember {
   bool _finalized = false;
   _MemberName _name;
 
-  final bool isStatic;
+  final String special;
   final _RawType returnType;
   final MdnProperty? mdnProperty;
   late final _MemberName name = _generateName();
 
-  _OverridableOperation._(this._name, this.isStatic, this.returnType,
+  _OverridableOperation._(this._name, this.special, this.returnType,
       this.mdnProperty, super.parameters);
 
-  factory _OverridableOperation(idl.Operation operation, _MemberName name,
+  factory _OverridableOperation(idl.Operation operation, _MemberName memberName,
           MdnProperty? mdnProperty) =>
-      _OverridableOperation._(name, operation.special == 'static',
+      _OverridableOperation._(memberName, operation.special,
           _getRawType(operation.idlType), mdnProperty, operation.arguments);
 
+  bool get isStatic => special == 'static';
+
   _MemberName _generateName() {
     // The name is determined after all updates are done, so finalize the
     // operation.
@@ -404,7 +410,8 @@ class _OverridableOperation extends _OverridableMember {
         'finalized.');
     final jsOverride = _name.jsOverride;
     final thisName = jsOverride.isNotEmpty ? jsOverride : _name.name;
-    assert(thisName == that.name && isStatic == (that.special == 'static'));
+    assert((that.name.isEmpty || thisName == that.name) &&
+        special == that.special);
     returnType.update(that.idlType);
     _processParameters(that.arguments);
   }
@@ -449,7 +456,7 @@ class _PartialInterfacelike {
         case 'constructor':
           if (!_shouldGenerateMember(name)) break;
           final idlConstructor = member as idl.Constructor;
-          if (_hasHTMLConstructorAttribute(idlConstructor)) continue;
+          if (_hasHTMLConstructorAttribute(idlConstructor)) break;
           if (constructor == null) {
             constructor = _OverridableConstructor(idlConstructor);
           } else {
@@ -487,16 +494,39 @@ class _PartialInterfacelike {
           break;
         case 'operation':
           final operation = member as idl.Operation;
-          final operationName = operation.name;
-          if (operationName.isEmpty) {
-            // TODO(joshualitt): We may be able to handle some unnamed
-            // operations.
-            continue;
+          final special = operation.special;
+          var operationName = operation.name;
+          // Some special operations may not have any MDN data and may be given
+          // a name that is irrelevant to the IDL, so avoid querying in that
+          // case and always emit.
+          var shouldQueryMDN = true;
+          switch (special) {
+            case 'getter':
+              if (operationName.isEmpty) {
+                operationName = 'operator []';
+                shouldQueryMDN = false;
+              }
+              break;
+            case 'setter':
+              if (operationName.isEmpty) {
+                operationName = 'operator []=';
+                shouldQueryMDN = false;
+              }
+              break;
+            case 'static':
+              break;
+            default:
+              // TODO(srujzs): Should we handle other special operations,
+              // unnamed or otherwise? For now, don't emit the unnamed ones and
+              // do nothing special for the named ones.
+              if (operationName.isEmpty) break;
           }
           final isStatic = operation.special == 'static';
-          if (!_shouldGenerateMember(operationName, isStatic: isStatic)) break;
-          final docs =
-              mdnInterface?.propertyFor(operationName, isStatic: isStatic);
+          if (shouldQueryMDN &&
+              !_shouldGenerateMember(operationName, isStatic: isStatic)) break;
+          final docs = shouldQueryMDN
+              ? mdnInterface?.propertyFor(operationName, isStatic: isStatic)
+              : null;
           // Static member may have the same name as instance members in the
           // IDL, but not in Dart. Rename the static member if so.
           if (isStatic) {
@@ -986,13 +1016,18 @@ class Translator {
 
   code.Method _operation(_OverridableOperation operation) {
     final memberName = operation.name;
+    // The IDL may return the value that is set. Dart doesn't let us use any
+    // type besides `void` for `[]=`, so we ignore the return value.
+    final returnType = memberName.name == 'operator []='
+        ? code.TypeReference((b) => b..symbol = 'void')
+        : _typeReference(operation.returnType, returnType: true);
     return _overridableMember<code.Method>(
       operation,
       (requiredParameters, optionalParameters) => code.Method((b) => b
         ..annotations.addAll(_jsOverride(memberName.jsOverride))
         ..external = true
         ..static = operation.isStatic
-        ..returns = _typeReference(operation.returnType, returnType: true)
+        ..returns = returnType
         ..name = memberName.name
         ..docs.addAll(operation.mdnProperty?.formattedDocs ?? [])
         ..requiredParameters.addAll(requiredParameters)