Script editor debugger - experimental

[karlaspuldaro]

Closes #975 - Integrate Script Editor with JupyterLab debugger

What changes were proposed in this pull request?

• Subclass ScriptEditor (R + Python): PR Add Script Editor language-specific subclasses #2388
• Get debugger service from activate plugin + create file debug handler
• Enable/disable debug button on kernel selection change
• Start debugger session for custom handler
• Update/restart debug session on kernelspec change
• Handle session on page reload
• Keep session connection open open after run when debug mode is on and selected kernel supports debugging
• Change stop button behavior to interrupt a kernel run and not shutdown a session connection
• Fix kernel spec init
• Fix/comment existing python editor / pipeline tests
• Add/update documentation

Know issues / Follow ups:

• Changing kernels disables debugging #2902
• Add basic debugger tests #2897
• Investigate script runner tests failing CI #2898
• Script editor kernel selector styling  #2899
• Upstream: bug - Interrupting the kernel while debugger is running does not trigger breakpoints on subsequent debug runs (same behavior on notebooks) - The terminate button does not work in the debugger jupyterlab/jupyterlab#11247
• Upstream: enhancement - Debugger side bar not minimized when disabling the debugger jupyterlab/jupyterlab#13018
• Upstream: enhancement - Improve debugger support to editing existing variables jupyterlab/jupyterlab#13019
• Refactor toolbar usage (move to @jupyterlab/ui-components library v4.0.0-alpha): Update ToolbarButton widget library #2375

How was this pull request tested?

No new test added for the experimental feature yet - debugger feature tested manually, tests to follow.
Existing script editor tests updated.

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[ptitzler]

A nice-to-have usability feature, perhaps for the future:

• If one enables the debugger, currently the debugger side panel is expanded.
  
• However, if one disables the debugger the panel is currently not minimized, forcing the user to do that manually.

[karlaspuldaro]

A nice-to-have usability feature, perhaps for the future:

• If one enables the debugger, currently the debugger side panel is expanded.
• However, if one disables the debugger the panel is currently not minimized, forcing the user to do that manually.

Agreed, the same behavior happens in notebooks so we can implement the enhancement upstream

[ptitzler]

minor edits for consistency and relevancy

[karlaspuldaro]

@ptitzler thx for reviewing! Comments are addressed.

[kiersten-stokes]

This is super cool! I just have a few documentation NITs below

[karlaspuldaro]

@kiersten-stokes thanks for the feedback!

[karlaspuldaro]

@akchinSTC thank you for the suggestions, doc updates addressed

[kiersten-stokes]

This is exciting!