Rework how we run/kill scripts and how we quit in ddbg.

Rework how we run/kill scripts and how we quit in ddbg.

-------------

Details:

Add a new Command class to ddbg and begin using it to implement
command dispatching, help, and completion.  I hope to migrate all the
commands to this pattern.

Since command dispatch now accepts command prefixes (e.g. 'q' for
'quit') I now use slightly longer command names.

The debugged program no longer starts automatically.  It can now be
started and stopped with the run/kill commands.

The set/show commands are added which provide a general way to
modify/query debugger settings.  For example, this can be used to
change the arguments passed to the debugged script or its vm
(e.g. 'set vmargs --myvmarg').

'q' -> 'quit'

'h' -> 'help'.  Also added command help, e.g. 'help run', 'help help'.
This is only implemented for the new commands so far.

Commando now exports a Stream instead of taking a command handler.
This makes it simpler to add error/done handlers for Commando.

Reworking ddbg quitting.  When the debugged process quits, the
debugger no longer quits.  When the user quits, try to kill the
debugged process, shut down the debugger connection, and shut down
commando.  When we get an unexpected error in Commando, try to handle
it better.  Whenever we quit, try to restore echomode/linemode.

Add a retry "loop" to handle the case where the debugged process takes
a bit to open its debug port.  This tends to happen a lot on the
second 'run' for some reason.

R=hausner@google.com

Committed: https://code.google.com/p/dart/source/detail?r=30871

[hausner, 2013-12-04 00:26:35]

LGTM with comments. Futures and streams are causing headaches when trying to
understand a program.

https://codereview.chromium.org/99963004/diff/40001/tools/ddbg.dart
File tools/ddbg.dart (right):

https://codereview.chromium.org/99963004/diff/40001/tools/ddbg.dart#newcode185
tools/ddbg.dart:185: var matchNames = matches.map((handler) => handler.name);
You could just print help for all the commands that match.

https://codereview.chromium.org/99963004/diff/40001/tools/ddbg.dart#newcode189
tools/ddbg.dart:189: print("Command not recognized.");
How about printing the usage here?

https://codereview.chromium.org/99963004/diff/40001/tools/ddbg.dart#newcode1066
tools/ddbg.dart:1066: 'help'];
Don't you need to add the new set and show commands?

https://codereview.chromium.org/99963004/diff/40001/tools/ddbg.dart#newcode1128
tools/ddbg.dart:1128: onError: (e) {
This is where Dart code becomes pretty much unreadable in my opinion. Too many
nested things going on here. To what does this onError parameter belong?

Not your fault.

https://codereview.chromium.org/99963004/diff/40001/tools/ddbg.dart#newcode1208
tools/ddbg.dart:1208: void main(List<String> args) {
Is it still possible to invoke ddbg without a target script, so that it connects
to a process that is already waiting at the debugger port?

[turnidge, 2013-12-04 19:35:20]

I've added two new commands, 'connect' and 'disconnect' which could stand
another look.

https://codereview.chromium.org/99963004/diff/40001/tools/ddbg.dart
File tools/ddbg.dart (right):

https://codereview.chromium.org/99963004/diff/40001/tools/ddbg.dart#newcode185
tools/ddbg.dart:185: var matchNames = matches.map((handler) => handler.name);
On 2013/12/04 00:26:35, hausner wrote:
> You could just print help for all the commands that match.

Nice idea.  Done.

https://codereview.chromium.org/99963004/diff/40001/tools/ddbg.dart#newcode189
tools/ddbg.dart:189: print("Command not recognized.");
On 2013/12/04 00:26:35, hausner wrote:
> How about printing the usage here?

I have improved this message to this:

> help fnord
Command 'fnord' not recognized.  Try 'help' for a list of commands.

https://codereview.chromium.org/99963004/diff/40001/tools/ddbg.dart#newcode1066
tools/ddbg.dart:1066: 'help'];
On 2013/12/04 00:26:35, hausner wrote:
> Don't you need to add the new set and show commands?

allCommands will be shrinking over time.  The second loop below, over
commandList, handles the new commands.  'help' and 'q' have now been removed
from allCommands and allCommands has been renamed oldCommands.

https://codereview.chromium.org/99963004/diff/40001/tools/ddbg.dart#newcode1128
tools/ddbg.dart:1128: onError: (e) {
On 2013/12/04 00:26:35, hausner wrote:
> This is where Dart code becomes pretty much unreadable in my opinion. Too many
> nested things going on here. To what does this onError parameter belong?
> 
> Not your fault.

Yes, hard to read here for sure.

The onError is a named parameter to the .then() function from the first line.  I
have added two helper functions "setupVmSocket" and "retryOpenVmSocket" which
makes the code look a bit less outlandish.

https://codereview.chromium.org/99963004/diff/40001/tools/ddbg.dart#newcode1208
tools/ddbg.dart:1208: void main(List<String> args) {
On 2013/12/04 00:26:35, hausner wrote:
> Is it still possible to invoke ddbg without a target script, so that it
connects
> to a process that is already waiting at the debugger port?

No.  I missed that.

I have now added two new commands, 'connect' and 'disconnect' that can be used
to attach to an already running process.

[turnidge, 2013-12-04 21:21:38]

Committed patchset #7 manually as r30871 (presubmit successful).

[hausner, 2013-12-04 23:48:20]

Still LGTM. Thanks for the improvements in functionality and readability.