Auto-attach to sub process (auto-reload of Django, Flask)

[DonJayamanne]

pydevd supports this today, all we need to do is just pass a flag.

[DonJayamanne]

@karthiknadig Please check whether this is required for VS

[zooba]

Isn't this the same as #57?

[karthiknadig]

The important distinction is the number of process that the adapter itself is attached to. I think in this case there will be one process that the adapter is expected to attach to or launch, and continue to be connected, even after template reload results in a new sub-process. Although I am not sure how the template breakpoints will work in this case, we have to test this to see if there are any other limitations.

[DonJayamanne]

I've created a separate issue for django, flask debugging due to an item added into the exit criteria of PTVSD. I do not want multi-process debugging not to get implemented simply because the VSC protocol doesn't support it. I.e. not being able to differentiate between the process ids when debugging (step in, step out, what process ids do threads belong to, etc).

In the case of auto-reloading of django templates, we (VSC) don't care whether its mult-process or not. All we care about is breaking into the code and supporting breakpoints (i.e. standard debugging). I.e. process id doesn't matter.

[karthiknadig]

User feedback:

I used to use Pyramid, and the VSC debugger doesn't handle the option "--reload" (provided by Pyramid) and the multi-threaded process, then the breakpoints don't work.
I have a warning from pydev debugger :
pydev debugger: New process is launching (breakpoints won't work in the new process).
pydev debugger: To debug that process please enable 'Attach to subprocess automatically while debugging?' option in the debugger settings.

Anyway, the breakpoint work without the --reload option, but I need to restart the server at any changes in the code

[int19h]

This is implemented in insider builds now. We have another more generic epic, #1706, open to track the overall multiproc work - this has the information on how to enable it. We'll use that one to track the release progress (i.e. it will be closed once we ship a stable version with the new bits).