Handle debugger lifecycle

[jtpio]

Fixes #292.

A couple of fixes as a follow-up to #239.

To try it out:

TODO

• Turn debugging off when the sidebar is closed
• Notebook and console handlers lifecycle should follow the toggle button
• Create the sidebar when enabling debugging via the button if it does not exist yet. Otherwise: do not show the switch button if there is no sidebar? (Can be handled separately)

Keep last debug session

Handle widgets with the same session

Restore the state from the kernel

Remove the recently added debuggedClients to stay stateless

[jtpio]

To make the experience less confusing and to avoid starting and stopping the debugger, we should tie the handlers lifecycle to the toggle button, and whether debugging is enabled for a given session path:

[jtpio]

It turns out that the toggle button logic needed quite some refactoring. The main takeaway is that toggling the button should also create and dispose the debug handlers properly.

This change also removes the debuggedClient state that was introduced in #239, so the debugger still stays stateless.

To try it out:

As an improvement, we could consider adding a signal to the debug session, so the UI can update itself when the state of the session changes (started or stopped). For now we have to focus back on the widget to have the UI changes propagated.

[jtpio]

The second main change is that we now don't create a DebugSession anymore for a client that doesn't support debugging.

This allows the debugger to keep "focus" on the previous client that supports debugging. As a side-effect we can inspect variables for a notebook being debugged, while working on a notebook that doesn't have support for debugging:

[afshin]

So good, negative delta pull request!

👍

[jtpio]

Will do a quick update to:

• move DebugSession#requestDebuggingEnabled to IDebugger#isAvailable
• guarantee IDebugger#isAvailable returns a boolean

[KsavinN]

Locally it works well :)

Don't know why but I see that button changed shape to a circle. (That bug was only in Binder)

[afshin]

Hm, @KsavinN, try running a git clean -fdx before rebuilding, maybe? I see the correct toggle when I build it.

[KsavinN]

Hm, @KsavinN, try running a git clean -fdx before rebuilding, maybe? I see the correct toggle when I build it.

I did it locally. It's work properly. That bug appears during using a binder.

[jtpio]

Also seeing that on Binder, but not locally.

[afshin]

@jtpio I guess it should just be a method on DebugService that is exposed on the IDebugger interface.

[jtpio]

That sounds like the best option indeed.

[jtpio]

For Binder and the toggle button, it looks like an issue with JupyterLab 1.1.4 (which is used on Binder for now). Or maybe just the 1.1 series.

This can be reproduced locally in a fresh environment:

conda create -n debugger-test -c conda-forge jupyterlab=1.1.4 xeus-python ptvsd
jupyter labextension install @jupyterlab/debugger --debug
jupyter lab xpython_example.ipynb

We are probably all using 1.2+ locally.

[jtpio]

This should be ready to go now, cc @afshin @KsavinN if you want to have another look.

[afshin]

Thanks!