Weird things happen when I debug + preLaunchTask

[roblourens]

Trying to verify #82076

• Followed the setup steps in the issue, installed Eric's webpack problem matcher extension
• I got into a state where the task was running, but starting a debug session didn't work, it just hung at the debug viewlet progress bar
• I kill the task and the pending debug session
• I tried to start it again, and nothing happened
• I looked around for logs, didn't see any errors
• Then suddenly I had 3 instances of the same task running, and 3 instances of the debug session
• Killed them all, and the call stack still showed two debug sessions (but there was no debug viewlet)

[alexr00]

I can't get the many instances of the task running, but I do see the debug session starting even after I cancel it.
Steps:

• Start a debug config with a slow background prelaunch task
• Wait for the task to start, but not finish
• Cancel the debug session before the task finishes, but let the task keep running
• When the task completes the debug starts even though I cancelled it.

[isidorn]

I think we always had this behavior. Unfortunetly I will not have time to tackle this in the endgame. Thus moving to next milestone
Here's a code poitner in case somebody is interested in investigating in the meantime
https://github.com/Microsoft/vscode/blob/721f2274694681dadd860dc2a6e5c986f869b6df/src/vs/workbench/contrib/debug/browser/debugService.ts#L768

[isidorn]

I was able to reproduce what @alexr00 mentioned here
I have pushed a fix for this particular behavior with follow up work captured here #87638