Properly handle debug console completion

[martin-fleck-at]

What it does

• Ensure console session is disposed when debug session is destroyed
• Remove monaco completion item provider on disposal
• Ensure we only provide completion items for our own session
• Sync debug console with the currently selected session

Fixes #10468
Fixes #10648

How to test

1. Install Java Debugger
2. Create two simple Java programs with one variable to test the completion capabilities
3. Run both debugging sessions at once and try to use completion in the Debug Console
4. Switch between debug session consoles to see if completion items are available and only provided for the selected session

Review checklist

• As an author, I have thoroughly tested my changes and carefully followed the review guidelines

Reminder for reviewers

• As a reviewer, I agree to behave in accordance with the review guidelines

[msujew]

Sync debug console with the currently selected session

It seems to me like this isn't working correctly. When clicking on another thread in the threads view (using the JS debugger), the select element gets blanked out. Only when clicking on the actual root debug session the correct option is selected:

2021-11-29.16-13-40.mp4

The issue is probably related to the changes I did in #9613. Due to these changes, some debug sessions share the same console session while others don't. This has to be reflected in the selection logic.

[colin-grant-work]

Functionally this seems to be working for me, though perhaps @msujew can test some of the intricacies of parent and child sessions, since he's worked on that recently.

Aside from that, a few comments on the implementation.

[martin-fleck-at]

@colin-grant-work Thank you very much for your feedback! I changed the things you mentioned and hopefully everything is now up to par.

[colin-grant-work]

The new changes look good to me, and it is now possible to get auto-completion in the debug console. From that perspective, I would consider the PR complete. However, the functionality of the debug console still seems fairly broken, as described here. This PR addresses one of the logs mentioned there: Unknown request: completions is no longer logged, but I still see Unknown request: evaluate when entering code in a Mocha debugging session in the Theia repo. I would guess that the cause is similar to the problem here: we're not sending the request to the right session. Would you be interested in addressing that problem as part of this PR, or would you prefer to limit this PR to the completion problem and address execution separately?

[martin-fleck-at]

@colin-grant-work Ah, I see what you mean and I had a quick look at it. You are right that we also used the wrong session for the request for the evaluate request. I pushed a new commit on top which should fix that.

[colin-grant-work]

With the latest changes, both completion and execution work as expected. 👍

[JonasHelming]

@vince-fugnitto @msujew : Any final remarks, otherwise I would merge this

[msujew]

When using the node debugger, the completion does not to work correctly when manually triggering the completion (Ctrl+Space). I'm not completely sure what's wrong there:

2022-01-31.14-39-22.mp4

While typing the completion seems to work correctly, but when triggering it manually, an empty completion box appears (visible at the end of the video). Also, when pressing Ctrl+Space without any input, only the name of the debug session appears.

[martin-fleck-at]

@msujew Thank you for your fast response! I had a look at this and the box with the debug session name without any input is the expected behavior if you compare it with VS Code. As far as I can see, this is actually what the debug adapter returns.

As for the "empty" box, it turns out that this is a message box saying 'No suggestions.' that is just placed "badly". The VS Code suggestion widget shows suggestions above the input but messages like 'Loading' and 'No suggestions.' below. The big difference is that in VS Code the message box is actually properly rendered ABOVE the status bar at the bottom, so you can actually read the message. You can test the suggestion widget in Theia in any editor that supports suggestions. You'll see how the different things are rendered. So the problem we have is that there is not enough space at the bottom of our console views.

I tried looking for a pure CSS solution but unfortunately I could not find anything satisfying. The problem is that the suggest-widget provides the surrounding container (with border, background colors, sash handles etc.) while either showing the .tree child with the suggestions or the .message child with messages. We can query which one of those is visible but we cannot move the parent suggest widget based on that (like margin: -50px) as we do not have a proper parent selector.

Do you, by any chance, have any idea how we can achieve this without restructuring the DOM? Otherwise I'd probably open up a separate issue as it is unrelated to the actual functionality of completion. What do you think?

[msujew]

@martin-fleck-at Ha, interesting. You're right, VSCode also exhibits the same behavior. Seems to me like the node-debugger extension does not work as expected, but that's not on us to fix ;)

I don't have too much of an issue with the weirdly placed 'No suggestions' box, it just added to my already existing confusion.

So in that regard everything else works as expected and the code looks good to me 👍

[JonasHelming]

@martin-fleck-at : Could you squash, I will merge then

[martin-fleck-at]

@msujew Thank you for your fast response. Then I'll leave it as is.
@JonasHelming Thank you! I squashed and rebased the change. Now we only need to wait for the CI to run through.