fixes #173, ability to use native JS indexers

dom_experimental could opt-in to use this

Review URL: https://codereview.chromium.org/1145833004

Author: John Messerly

lib/src/codegen/js_codegen.dart

@@ -110,7 +110,7 @@ class JSCodegenVisitor extends GeneralizingAstVisitor with ConversionVisitor {
     if (unit.directives.isNotEmpty) {
       var libraryDir = unit.directives.first;
       if (libraryDir is LibraryDirective) {
-        var jsName = getAnnotationValue(libraryDir, _isJsNameAnnotation);
+        var jsName = findNodeAnnotation(libraryDir, _isJsNameAnnotation);
         jsDefaultValue = getConstantField(jsName, 'name', types.stringType);
       }
     }
@@ -329,7 +329,7 @@ class JSCodegenVisitor extends GeneralizingAstVisitor with ConversionVisitor {
     // If we've already emitted this class, skip it.
     var classElem = node.element;
     var type = classElem.type;
-    var jsName = getAnnotationValue(node, _isJsNameAnnotation);
+    var jsName = findNodeAnnotation(node, _isJsNameAnnotation);
 
     if (jsName != null) return _emitJsType(node.name.name, jsName);
 
@@ -350,7 +350,7 @@ class JSCodegenVisitor extends GeneralizingAstVisitor with ConversionVisitor {
         _classHeritage(classElem), _emitClassMethods(node, ctors, fields));
 
     String jsPeerName;
-    var jsPeer = getAnnotationValue(node, _isJsPeerInterface);
+    var jsPeer = findNodeAnnotation(node, _isJsPeerInterface);
     if (jsPeer != null) {
       jsPeerName = getConstantField(jsPeer, 'name', types.stringType);
     }
@@ -475,7 +475,7 @@ class JSCodegenVisitor extends GeneralizingAstVisitor with ConversionVisitor {
       jsMethods.add(_emitImplicitConstructor(node, fields));
     }
 
-    bool hasJsPeer = getAnnotationValue(node, _isJsPeerInterface) != null;
+    bool hasJsPeer = findNodeAnnotation(node, _isJsPeerInterface) != null;
 
     bool hasIterator = false;
     for (var m in node.members) {
@@ -1349,7 +1349,12 @@ class JSCodegenVisitor extends GeneralizingAstVisitor with ConversionVisitor {
 
   JS.Expression _emitSet(Expression lhs, Expression rhs) {
     if (lhs is IndexExpression) {
-      return _emitSend(_getTarget(lhs), '[]=', [lhs.index, rhs]);
+      var target = _getTarget(lhs);
+      if (_useNativeJsIndexer(target.staticType)) {
+        return js.call(
+            '#[#] = #', [_visit(target), _visit(lhs.index), _visit(rhs)]);
+      }
+      return _emitSend(target, '[]=', [lhs.index, rhs]);
     }
 
     Expression target = null;
@@ -2116,9 +2121,18 @@ class JSCodegenVisitor extends GeneralizingAstVisitor with ConversionVisitor {
 
   @override
   visitIndexExpression(IndexExpression node) {
-    return _emitSend(_getTarget(node), '[]', [node.index]);
+    var target = _getTarget(node);
+    if (_useNativeJsIndexer(target.staticType)) {
+      return new JS.PropertyAccess(_visit(target), _visit(node.index));
+    }
+    return _emitSend(target, '[]', [node.index]);
   }
 
+  // TODO(jmesserly): ideally we'd check the method and see if it is marked
+  // `external`, but that doesn't work because it isn't in the element model.
+  bool _useNativeJsIndexer(DartType type) =>
+      findElementAnnotation(type.element, _isJsIndexerAnnotation) != null;
+
   /// Gets the target of a [PropertyAccess] or [IndexExpression].
   /// Those two nodes are special because they're both allowed on left side of
   /// an assignment expression and cascades.
@@ -2636,6 +2650,9 @@ String jsOutputPath(LibraryInfo info, Uri root) {
 // TODO(jmesserly): validate the library. See issue #135.
 bool _isJsNameAnnotation(DartObjectImpl value) => value.type.name == 'JsName';
 
+bool _isJsIndexerAnnotation(DartObjectImpl value) =>
+    value.type.name == 'JsIndexer';
+
 bool _isJsPeerInterface(DartObjectImpl value) =>
     value.type.name == 'JsPeerInterface';
 

lib/src/utils.dart

@@ -349,7 +349,7 @@ String resourceOutputPath(Uri resourceUri, Uri entryUri) {
 ///
 ///    (v) => v.type.name == 'Deprecated' && v.type.element.library.isDartCore
 ///
-DartObjectImpl getAnnotationValue(
+DartObjectImpl findNodeAnnotation(
     AnnotatedNode node, bool test(DartObjectImpl value)) {
   for (var metadata in node.metadata) {
     ElementAnnotationImpl element = metadata.elementAnnotation;
@@ -364,6 +364,19 @@ DartObjectImpl getAnnotationValue(
   return null;
 }
 
+/// Similar to [findNodeAnnotation] but starts from any element.
+DartObjectImpl findElementAnnotation(
+    Element element, bool test(DartObjectImpl value)) {
+  for (var metadata in element.metadata) {
+    var evalResult = metadata.evaluationResult;
+    if (evalResult == null) continue;
+
+    var value = evalResult.value;
+    if (value != null && test(value)) return value;
+  }
+  return null;
+}
+
 /// Given a constant [value], a [fieldName], and an [expectedType], returns the
 /// value of that field.
 ///

test/codegen/domtest.dart

@@ -0,0 +1,16 @@
+// Copyright (c) 2015, 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.
+
+library domtest;
+
+import 'sunflower/dom.dart';
+
+// https://github.com/dart-lang/dev_compiler/issues/173
+testNativeIndexers() {
+  var nodes = document.querySelector('body').childNodes;
+  for (int i = 0; i < nodes.length; i++) {
+    print(nodes[i]);
+    print(nodes[i] = null);
+  }
+}

test/codegen/expect/domtest.js

@@ -0,0 +1,16 @@
+var domtest = dart.defineLibrary(domtest, {});
+var dom = dart.import(dom);
+var core = dart.import(core);
+(function(exports, dom, core) {
+  'use strict';
+  // Function testNativeIndexers: () → dynamic
+  function testNativeIndexers() {
+    let nodes = dom.document.querySelector('body').childNodes;
+    for (let i = 0; dart.notNull(i) < dart.notNull(nodes.length); i = dart.notNull(i) + 1) {
+      core.print(nodes[i]);
+      core.print(nodes[i] = null);
+    }
+  }
+  // Exports:
+  exports.testNativeIndexers = testNativeIndexers;
+})(domtest, dom, core);

test/codegen/expect/domtest.txt

@@ -0,0 +1 @@
+// Messages from compiling domtest.dart

test/codegen/expect/sunflower/dom.js

@@ -19,8 +19,11 @@ var core = dart.import(core);
     constructors: () => ({Overload: [Overload, []]})
   });
   let overload = dart.const(new Overload());
+  class JsIndexer extends core.Object {
+    JsIndexer() {
+    }
+  }
   let EventListener = dart.typedef('EventListener', () => dart.functionType(dart.void, [Event]));
-  class Event extends core.Object {}
   let InputElement = HTMLInputElement;
   let CanvasElement = HTMLCanvasElement;
   class RenderingContext extends core.Object {}
@@ -41,8 +44,8 @@ var core = dart.import(core);
   exports.JsName = JsName;
   exports.Overload = Overload;
   exports.overload = overload;
+  exports.JsIndexer = JsIndexer;
   exports.EventListener = EventListener;
-  exports.Event = Event;
   exports.InputElement = InputElement;
   exports.CanvasElement = CanvasElement;
   exports.RenderingContext = RenderingContext;

test/codegen/sunflower/dom.dart

@@ -19,6 +19,10 @@ class Overload {
 }
 const overload = const Overload();
 
+class JsIndexer {
+  const JsIndexer();
+}
+
 external Document get document;
 
 @JsName(name: 'Document')
@@ -30,10 +34,27 @@ abstract class Document {
 abstract class Element {
   void addEventListener(String type, EventListener callback, [bool capture]);
   String textContent;
+  NodeList get childNodes;
+}
+
+@JsName()
+class Node {}
+
+@JsName()
+@JsIndexer()
+class NodeList {
+  external NodeList();
+  external num get length;
+  external set length(num _);
+  external Node item(num index);
+
+  external Node operator [](num index);
+  external void operator []=(num index, Node);
 }
 
 typedef void EventListener(Event e);
 
+@JsName()
 abstract class Event {}
 
 @JsName(name: 'HTMLInputElement')