debug: clean up debug session management

[tsmaeder]

Bug Description:

Whe only remove debug sessions when the debuggee sends an "exited" event. However, when we press the "stop" button in the UI, we're sending a 'terminate' request to the debuggee...this just asks the debuggee to terminate the debug session not to exit the process. So we end up with a stale debug session we cannot get rid of.

Steps to Reproduce:

1. Install the mock debug extension (probably attaching to a long-running java process works, as well) (see Add DebugAdapterNamedPipeServer and DebugAdapterInlineImplementation #10163 for instructions)
2. Launch a moch debug sessions
3. Press the "stop" button on the debug session
4. Observe. the session remains.

I believe we should get rid of the debug session upon 'terminated', not 'exited'.

Additional Information

• Operating System:
• Theia Version: 1.18.0 master

[svor]

Can see this problem when running Theia with redhat.java-0.82.0.vsix and vscode-java-debug-0.35.0.vsix

screencast-localhost_3000-2021.10.04-17_50_00.mp4

[tsmaeder]

@alvsan09 are you going to work on this, because I was going to.

[alvsan09]

@alvsan09 are you going to work on this, because I was going to.

I started looking into it but I have been a bit distracted from it,
It's a good time to take it over if you like 👍
Thanks for reaching out !

[tsmaeder]

Stole it ;-)

[msujew]

@tsmaeder do you plan to finish this during this month? One of our customers experiences an issue related to this (in this case, the debuggee sometimes throws an exception when trying to terminate the session, resulting in Theia never disposing the session, see arduino/arduino-ide#527)

If you don't have time, I'd like to take this on.

[tsmaeder]

I'm currently working on a fix, but t.b.h it's not obvious how to track the lifecycle of nested debug sessions, debug adapters and debuggees. Still seeing lots of surprises.

[tsmaeder]

@msujew If terminating the debuggee fails, isn't it correct behaviour to keep the debug session? What behaviour do you expect? What happens when the debuggee is killed by hand?