Throw ArgumentError if packageRoot is null.

dart/pkg/compiler/samples/jsonify/jsonify.dart

Index: dart/pkg/compiler/samples/jsonify/jsonify.dart
diff --git a/dart/pkg/compiler/samples/jsonify/jsonify.dart b/dart/pkg/compiler/samples/jsonify/jsonify.dart
index bb0c41370193c99c131eed32e9902425572e28e7..9b70921b21fccbe85226d9e9895a3fd577d6881b 100644
--- a/dart/pkg/compiler/samples/jsonify/jsonify.dart
+++ b/dart/pkg/compiler/samples/jsonify/jsonify.dart
@@ -46,7 +46,12 @@ main(List<String> arguments) {
   Uri myLocation =
       handler.provider.cwd.resolveUri(Platform.script);
 
-  sdkRoot = myLocation.resolve(SDK_ROOT).resolve('../');
+  Uri packageRoot =
+      handler.provider.cwd.resolve(Platform.packageRoot);

[Johnni Winther, 2015/01/08 08:16:15]

You need to ensure that the URI path ends with a /

[Platform.packageRoot] is _not_ the resolved base Uri but just the user-provided
string.

[ahe, 2015/01/08 08:34:43]

This isn't a super user friendly tool. For example, on line 43, an error will be
thrown if [arguments] is empty. I would rather not clutter this code with
handling of exceptional cases. Also, it isn't necessary, this tool doesn't read
packages.

In addition, it is possible to provide a usable package root which doesn't end
with a slash. It probably makes sense for dart2js (a directly user facing tool)
to complain about absence of a trailing slash, but I'm not convinced it is the
right trade-off for more low-level tools.

I'm going to submit this as-is, but please let me know if you disagree with my
analysis. I can create a follow-up CL.

[Johnni Winther, 2015/01/08 09:40:42]

The problem is really with Platform.packageRoot which should have been a fully
resolved URI.

+
+  Uri libraryRoot = myLocation.resolve(SDK_ROOT);
+
+  sdkRoot = libraryRoot.resolve('../');
 
   // Get the names of public dart2js libraries.
   Iterable<String> names = LIBRARIES.keys.where(isPublicDart2jsLibrary);
@@ -54,7 +59,7 @@ main(List<String> arguments) {
   // Turn the names into uris by prepending dart: to them.
   List<Uri> uris = names.map((String name) => Uri.parse('dart:$name')).toList();
 
-  analyze(uris, myLocation.resolve(SDK_ROOT), null, handler.provider, handler)
+  analyze(uris, libraryRoot, packageRoot, handler.provider, handler)
       .then(jsonify);
 }