Allow setting break-on-exceptions option over the service protocol.

runtime/observatory/lib/src/elements/debugger.dart

Index: runtime/observatory/lib/src/elements/debugger.dart
diff --git a/runtime/observatory/lib/src/elements/debugger.dart b/runtime/observatory/lib/src/elements/debugger.dart
index 70d8516ff539f8d31408ccb54130f90c5090211f..6f4c39f7690e059b10659c85977f6cfb50002d32 100644
--- a/runtime/observatory/lib/src/elements/debugger.dart
+++ b/runtime/observatory/lib/src/elements/debugger.dart
@@ -366,6 +366,34 @@ class FinishCommand extends DebuggerCommand {
       'Syntax: finish\n';
 }
 
+class BreakOnExceptionsCommand extends DebuggerCommand {
+  BreakOnExceptionsCommand(Debugger debugger)
+      : super(debugger, 'break-on-exceptions', []);

[rmacnak, 2015/06/11 17:31:17]

Don't really want to introduce the first hyphenated command...

[Cutch, 2015/06/11 21:20:12]

What about a 'set' command for configuring behaviour?

[rmacnak, 2015/06/12 00:09:38]

Somewhat better.

+
+  Future run(List<String> args) async {
+    if (args.length == 0) {
+      var result = await debugger.isolate.getExceptionPauseInfo();
+      debugger.console.print(result.toString());
+    } else if (args.length == 1) {
+      var result = await debugger.isolate.setExceptionPauseInfo(args[0]);
+      debugger.console.print(result.toString());
+    } else {
+      debugger.console.print("break-on-exceptions expects 0 or 1 argument");
+    }
+  }
+
+  String helpShort =
+      'Set the break-on-exceptions policy: all, none or unhandled';
+
+  String helpLong =
+      'Set the break-on-exceptions policy: all, none or unhandled'
+      '\n'
+      'Syntax: break-on-exceptions "all" | "none" | "unhandled"'
+      '- Set the policy\n'
+      '        break-on-exceptions                             '
+      '- Query the policy\n';
+}
+
 class BreakCommand extends DebuggerCommand {
   BreakCommand(Debugger debugger) : super(debugger, 'break', []);
 
@@ -856,6 +884,7 @@ class ObservatoryDebugger extends Debugger {
         new StepCommand(this),
         new FinishCommand(this),
         new BreakCommand(this),
+        new BreakOnExceptionsCommand(this),
         new ClearCommand(this),
         new DeleteCommand(this),
         new InfoCommand(this),
@@ -992,9 +1021,12 @@ class ObservatoryDebugger extends Debugger {
           console.print('Paused at breakpoint ${bpId} at '
                         '${script.name}:${line}:${col}');
         } else if (event.exception != null) {
-          // TODO(turnidge): Test this.
-          console.print('Paused due to exception ${event.exception} at '
+          console.print('Paused due to exception at '
                         '${script.name}:${line}:${col}');
+          // This seems to be missing if we are paused-at-exception after
+          // paused-at-isolate-exit. Maybe we shutdown part of the debugger too
+          // soon?
+          console.printRef(event.exception);
         } else {
           console.print('Paused at ${script.name}:${line}:${col}');
         }