Added Area-Library, Library-Isolate, Triaged labels.

Changed the title to: "Future returned from Isolate.spawnUri(bad library) does not complete".

Reassigning to VM.

When running the given example I see the following output:
===
$ out/ReleaseIA32/dart /tmp/bug.dart
in ShutdownIsolate: Unable to resolve function 'main' in library 'file:///tmp/bad.dart'.
===

The error comes from isolate.cc:595 ShutdownIsolate, and it doesn't look like the Dart side gets to see the error.

I'm willing to dig deeper, but I would prefer if the VM devs have a look first.

cc @a-siva.
cc @iposva-google.
Removed Area-Library label.
Added Area-VM label.

The problem is still reproducible at least on Dart VM version: 1.17.1 (Fri Jun 10 04:58:25 2016) on "windows_x64". I think it is important to fix this, because it will make Dart more programmer-friendly.

The problem is still reproducible at least on Dart VM version: 1.20.1 (Wed Oct 12 15:07:45 2016) on "windows_x64"

@alsemenov Apologies that nobody looked at this issue for so long.

I have just tried to reproduce the issue and it seems that one does get a meaningful error message one can act upon:

import 'dart:io';
import 'dart:isolate';

main() async {
  // Notice that "bar.dart" doesn't contain a "main" function.
  File('bad.dart').writeAsStringSync('foo() {}');

  try {
    await Isolate.spawnUri(Uri.parse('bad.dart'), [], null);
  } catch (e) {
    print('Got error: $e');
  }
}

This will print an error and exit the program (i.e. not hang):

% dart test.dart
Got error: IsolateSpawnException: Unable to spawn isolate: Dart_LoadScriptFromKernel: The binary program does not contain 'main'.
% 

This issue seems to be fixed.