Support user generated custom native JS classes.

pkg/compiler/lib/src/patch_parser.dart

 // Copyright (c) 2012, 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.
 
 /**
  * This library contains the infrastructure to parse and integrate patch files.
  *
  * Three types of elements can be patched: [LibraryElement], [ClassElement],
  * [FunctionElement]. Patches are introduced in patch libraries which are loaded
  * together with the corresponding origin library. Which libraries that are
@@ skipping 115 matching lines @@
 import 'diagnostics/messages.dart' show
     MessageKind;
 import 'elements/elements.dart';
 import 'elements/modelx.dart' show
     BaseFunctionElementX,
     ClassElementX,
     GetterElementX,
     LibraryElementX,
     MetadataAnnotationX,
     SetterElementX;
+import 'js_backend/js_backend.dart' show
+    JavaScriptBackend;
 import 'library_loader.dart' show
     LibraryLoader;
 import 'parser/listener.dart' show
     Listener,
     ParserError;
 import 'parser/element_listener.dart' show
     ElementListener;
 import 'parser/member_listener.dart' show
     MemberListener;
 import 'parser/partial_elements.dart' show
@@ skipping 150 matching lines @@
 }
 
 void patchElement(Compiler compiler,
                   Element origin,
                   Element patch) {
   if (origin == null) {
     compiler.reportErrorMessage(
         patch, MessageKind.PATCH_NON_EXISTING, {'name': patch.name});
     return;
   }
+
   if (!(origin.isClass ||
         origin.isConstructor ||
         origin.isFunction ||
         origin.isAbstractField)) {
     // TODO(ahe): Remove this error when the parser rejects all bad modifiers.
     compiler.reportErrorMessage(origin, MessageKind.PATCH_NONPATCHABLE);
     return;
   }
   if (patch.isClass) {
     tryPatchClass(compiler, origin, patch);
@@ skipping 42 matching lines @@
   checkNativeAnnotation(compiler, patch);
 }
 
 /// Check whether [cls] has a `@Native(...)` annotation, and if so, set its
 /// native name from the annotation.
 checkNativeAnnotation(Compiler compiler, ClassElement cls) {
   EagerAnnotationHandler.checkAnnotation(compiler, 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:
 /// - match the annotation syntactically and assume that the annotation is valid
 ///   if it looks correct,
 /// - setup a deferred action to check that the annotation has a valid constant
 ///   value and report an internal error if not.
 abstract class EagerAnnotationHandler<T> {
   /// Checks that [annotation] looks like a matching annotation and optionally
   /// applies actions on [element]. Returns a non-null annotation marker if the
@@ skipping 67 matching lines @@
                 Element element,
                 MetadataAnnotation annotation,
                 ConstantValue constant) {
     if (constant.getType(compiler.coreTypes).element !=
             compiler.nativeAnnotationClass) {
       compiler.internalError(annotation, 'Invalid @Native(...) annotation.');
     }
   }
 }
 
+/// 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.markAsJsInterop();
+    }
+    // Due to semantics of apply in the baseclass we have to return null to
+    // indicate that no match was found.
+    return hasJsInterop ? true : null;
+  }
+
+  @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();
 
   PatchVersion getPatchVersion(MetadataAnnotation annotation) {
     if (annotation.beginToken != null) {
       if (annotation.beginToken.next.value == 'patch') {
         return const PatchVersion(null);
       } else if (annotation.beginToken.next.value == 'patch_full') {
         return const PatchVersion('full');
@@ skipping 166 matching lines @@
 
 class PatchVersion {
   final String tag;
 
   const PatchVersion(this.tag);
 
   bool isActive(String patchTag) => tag == null || tag == patchTag;
 
   String toString() => 'PatchVersion($tag)';
 }