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 332 matching lines @@
 
 void patchClass(Compiler compiler,
                 ClassElementX origin,
                 ClassElementX patch) {
   if (origin.isPatched) {
     compiler.internalError(origin,
         "Patching the same class more than once.");
   }
   origin.applyPatch(patch);
   checkNativeAnnotation(compiler, patch);
+  checkJsInteropAnnotation(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, ClassElement cls) {
+  EagerAnnotationHandler.checkAnnotation(compiler, cls,
+      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 70 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 `@JsName(...)`
+/// annotations.
+class JsInteropAnnotationHandler implements EagerAnnotationHandler<String> {
+  const JsInteropAnnotationHandler();
+
+  String getJsNameAnnotation(MetadataAnnotation annotation) {
+    if (annotation.beginToken != null &&
+        annotation.beginToken.next.value == 'JsName') {
+      // Skipping '@', 'JsName', and '('.
+      Token argument = annotation.beginToken.next.next.next;
+      return (argument is StringToken) ? argument.value : '';
+    }
+
+    return null;
+  }
+
+  String apply(Compiler compiler,
+             Element element,
+             MetadataAnnotation annotation) {
+    if (element.isClass) {
+      String jsName = getJsNameAnnotation(annotation);
+      if (jsName != null) {
+        ClassElementX declaration = element.declaration;
+        // We do not track the class names for JsName annotations as we are not
+        // concerned about checked mode errors these classes.
+        declaration.isJsInterop = true;
+        return jsName;
+      }
+    }
+    return null;
+  }
+
+  @override
+  void validate(Compiler compiler,
+                Element element,
+                MetadataAnnotation annotation,
+                ConstantValue constant) {
+  }
+}
+
 /// 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 129 matching lines @@
 
 class PatchVersion {
   final String tag;
 
   const PatchVersion(this.tag);
 
   bool isActive(String patchTag) => tag == null || tag == patchTag;
 
   String toString() => 'PatchVersion($tag)';
 }