work in progress: observable implementation using detailed change records

lib/src/codegen.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.
 
 /** Collects common snippets of generated code. */
 library codegen;
 
 import 'file_system/path.dart';
 import 'info.dart';
 import 'utils.dart';
 
 /**
  * Header with common imports, used in every generated .dart file.  If path is
  * null then there is no file associated with the template (used by testing
  * so we'll display <MEMORY> for file name.
  */
-String header(Path path, String libraryName) => """
+String header(Path path, String libraryName) {
+  var library = libraryName != null ? '\nlibrary $libraryName;\n' : '';
+  return """
 // Auto-generated from ${path != null ? path.filename : "<MEMORY>"}.
 // DO NOT EDIT.
-
-library $libraryName;
-
+$library
 $imports
 """;
+}
 
 // TODO(sigmund): include only those imports that are used by the code.
 String get imports => """
 import 'dart:html' as autogenerated;
 import 'dart:svg' as autogenerated_svg;
 import 'package:web_ui/web_ui.dart' as autogenerated;
 """;
 
 /** The code in .dart files generated for a web component. */
 // TODO(sigmund): omit [_root] if the user already defined it.
@@ skipping 86 matching lines @@
 String importList(Iterable<Path> imports) =>
   imports.mappedBy((url) => "import '$url';").join('\n');
 
 /**
  * Text corresponding to a directive, fixed in case the code is in a different
  * output location.
  */
 String directiveText(
     DartDirectiveInfo directive, LibraryInfo src, PathInfo pathInfo) {
   var buff = new StringBuffer();
-  var uri = pathInfo.transformUrl(src.inputPath, directive.uri);
+  var uri = directive.uri;
+  if (!directive.generated) {
+    // This file was not generated, so get the relative path to the input file.
+    uri = pathInfo.transformUrl(src.inputPath, uri);
+  }
   buff..add(directive.label)
       ..add(" '")
       ..add(uri.replaceAll("'", "\\'"))
       ..add("'");
   if (directive.prefix != null) {
     buff..add(' as ')
         ..add(directive.prefix);
   }
   if (directive.show != null) {
     buff..add(' show ')
         ..add(Strings.join(directive.show, ','));
   }
   if (directive.hide != null) {
     buff..add(' hide ')
         ..add(Strings.join(directive.hide, ','));
   }
   buff.add(';');
   return buff.toString();
 }