Implemented variable inspection when the debugger has started

[JohanMabille]

References

#9114

Code changes

This implementation is specific to the debugger package. The frontned now sends an inspectVariables request to the backend when the debugger has started and the code has not hit a breakpoint.

This can change can be tested with xeus-python 0.12.2 or with this branch of ipykernel.

There are still some issues (thus the WIP status):

• infinite loop of sending inspectVariables when the user restars the kernel
• defining variables such as dict breaks the behavior (nothing is displayed anymore, but the backend doe snot emit any error).

User-facing changes

When the debugger has started, the user can now see the variables that have been defined so far in the variables panel of the debugger sidebar.

Backwards-incompatible changes

The kernel must support the inspectVariable request. This means upgrading to xeus-python 0.12.3 in the tests (this can be done in another PR). There is no impact on ipykernel since the debugger will be supported in the next release only, and the support for inspectVariables has been implemented.

[jupyterlab-dev-mode]

Thanks for making a pull request to JupyterLab!

To try out this branch on binder, follow this link:

[jtpio]

Thanks!

This can change can be tested with xeus-python 0.12.2

Does it mean we should also consider updating the version of xeus-python on CI here (used for the tests)?

jupyterlab/scripts/ci_install.sh

Lines 52 to 55 in ec84e6b

	# The debugger tests require a kernel that supports debugging
	if [[ $GROUP == js-debugger ]]; then
	pip install xeus-python">=0.9.0,<0.10.0"
	fi

Or is the new 0.12.2 mostly about adding support for filtering variables for the inspectVariables request, and thus is a nice-to-have but not a strict requirement?

[JohanMabille]

Second option, xeus-python 0.12.2 is mostly about adding support for the inspectVariables requesr.

[JohanMabille]

xeus-python 0.12.3 is not available yet for all platforms on conda-forge, thus the failure.

EDIT: except that we install xeus-python from pypi ...

[jtpio]

Looks like the new wheels will have to be published to PyPI, since xeus-python is installed via pip:

jupyterlab/scripts/ci_install.sh

Lines 52 to 55 in ec84e6b

	# The debugger tests require a kernel that supports debugging
	if [[ $GROUP == js-debugger ]]; then
	pip install xeus-python">=0.9.0,<0.10.0"
	fi

In the meantime the PR can be tested on Binder: https://mybinder.org/v2/gh/JohanMabille/jupyterlab/inspect?urlpath=lab-dev

[JohanMabille]

@jtpio I've changed the approach here: a new signal handler is connected to the iopubMessage signal, and asked for the defined variables after an idel message whose parent message type is execute_request has been received.

I'm afraid we may miss updates of variables due to widgets, but this avoids storing an internal state.

[JohanMabille]

Back to old version of xeus-python, since the upgrade makes the tests fail. We can upgrade in a dedicated PR.

[JohanMabille]

I have commented out the "restart" test since it now requires xeus-python 0.12.3. However, upgrading xeus requires fixing other tests. I will upgrade and fix all the tests in another PR.

[JohanMabille]

[blink1073]

Super green!

[blink1073]

Thanks!

[lawrence-z-arabii]

I suppose it's off topic but any ideas why 'table view' is only partly of variable's window height and has its own scrollbar?

[jupyterlab 3.0.14]

[jtpio]

@lawrence-z-arabii do you mind opening a separate issue to track this? (if none already exists)

The variable inspection from this PR is not in 3.0.14 so it's probably not directly related to this change. But it is in 3.1.0a5 if you want to try it out.

Thanks!