work in progress: observable implementation using detailed change records

lib/src/codegen.dart

Index: lib/src/codegen.dart
diff --git a/lib/src/codegen.dart b/lib/src/codegen.dart
index baffd1b6fd5104d0c2a33d3de8084da493f9917e..0cd6163c1c42c30de3baf6f896ee283f1679ff01 100644
--- a/lib/src/codegen.dart
+++ b/lib/src/codegen.dart
@@ -14,14 +14,15 @@ import 'utils.dart';
  * 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 => """
@@ -128,7 +129,11 @@ String importList(Iterable<Path> imports) =>
 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("'", "\\'"))