Support user generated custom native JS classes.

pkg/compiler/lib/src/patch_parser.dart

Index: pkg/compiler/lib/src/patch_parser.dart
diff --git a/pkg/compiler/lib/src/patch_parser.dart b/pkg/compiler/lib/src/patch_parser.dart
index a2ec63cf7006cdbfc964892a24ed6e9844cfe6db..0b60945f2a97c3217fc30c035982289926ac683a 100644
--- a/pkg/compiler/lib/src/patch_parser.dart
+++ b/pkg/compiler/lib/src/patch_parser.dart
@@ -133,6 +133,8 @@ import 'elements/modelx.dart' show
     LibraryElementX,
     MetadataAnnotationX,
     SetterElementX;
+import 'js_backend/js_backend.dart' show
+    JavaScriptBackend;
 import 'library_loader.dart' show
     LibraryLoader;
 import 'parser/listener.dart' show
@@ -303,6 +305,7 @@ void patchElement(Compiler compiler,
         patch, MessageKind.PATCH_NON_EXISTING, {'name': patch.name});
     return;
   }
+
   if (!(origin.isClass ||
         origin.isConstructor ||
         origin.isFunction ||
@@ -365,6 +368,12 @@ checkNativeAnnotation(Compiler compiler, ClassElement cls) {
       const NativeAnnotationHandler());
 }
 
+checkJsInteropAnnotation(Compiler compiler, element) {
+  EagerAnnotationHandler.checkAnnotation(compiler, element,
+      const JsInteropAnnotationHandler());
+}
+
+
 /// Abstract interface for pre-resolution detection of metadata.
 ///
 /// The detection is handled in two steps:
@@ -397,12 +406,19 @@ abstract class EagerAnnotationHandler<T> {
       if (result != null) {
         // TODO(johnniwinther): Perform this check in
         // [Compiler.onLibrariesLoaded].
-        compiler.enqueuer.resolution.addDeferredAction(element, () {
+        // TODO(jacobr): annotation resolution needs to be refactored.
+        actionCallback() {
           annotation.ensureResolved(compiler.resolution);
           handler.validate(
               compiler, element, annotation,
               compiler.constants.getConstantValue(annotation.constant));
-        });
+        }
+        if (compiler.enqueuer.resolution.queueIsClosed) {
+          actionCallback();

[Siggi Cherem (dart-lang), 2015/10/06 22:38:02]

I was hoping that now that you moved the logic to `onCodegenStartup`, we should
be able to revert this change

[Jacob, 2015/10/13 01:19:24]

me too.. reverted.

+        } else {
+          compiler.enqueuer.resolution.addDeferredAction(element,
+              actionCallback);
+        }
         return result;
       }
     }
@@ -452,6 +468,37 @@ class NativeAnnotationHandler implements EagerAnnotationHandler<String> {
   }
 }
 
+/// Annotation handler for pre-resolution detection of `@Js(...)`
+/// annotations.
+class JsInteropAnnotationHandler implements EagerAnnotationHandler<bool> {
+  const JsInteropAnnotationHandler();
+
+  bool hasJsNameAnnotation(MetadataAnnotation annotation) =>
+      annotation.beginToken != null && annotation.beginToken.next.value == 'Js';
+
+  bool apply(Compiler compiler,
+             Element element,
+             MetadataAnnotation annotation) {
+    bool hasJsInterop = hasJsNameAnnotation(annotation);
+    if (hasJsInterop) {
+      element.setHasJsInterop();
+    }
+    return hasJsInterop == true ? true : null;

[Siggi Cherem (dart-lang), 2015/10/06 22:38:02]

might be worth a tiny comment on why not return false (probably something to do
with the semantics of apply in the baseclass?)

[Jacob, 2015/10/13 01:19:24]

Done.

+  }
+
+  @override
+  void validate(Compiler compiler,
+                Element element,
+                MetadataAnnotation annotation,
+                ConstantValue constant) {
+    JavaScriptBackend backend = compiler.backend;
+    if (constant.getType(compiler.coreTypes).element !=
+        backend.jsAnnotationClass) {
+      compiler.internalError(annotation, 'Invalid @Js(...) annotation.');
+    }
+  }
+}
+
 /// Annotation handler for pre-resolution detection of `@patch` annotations.
 class PatchAnnotationHandler implements EagerAnnotationHandler<PatchVersion> {
   const PatchAnnotationHandler();