Implement CancellationToken logic for withProgress API

[matt-dot]

What it does

• Unlocks functionality of token.onCancellationRequested & token.isCancellationRequested (from the VS Code Extension API)
• Fixes Cancellation functionality for withProgress API  #11030

How to test

• Clone this VS Code Example and open in Theia
• Run the Launch Extension launch configuration
• Add a console.log within the setTimeout callbacks here to check the value of token.isCancellationRequested
• Run the extension's showProgress command (using the command pallette) and press the cancel button contained in the notification
• Pre-changes
  • No console output from within token.onCancellationRequested
  • token.isCancellationRequested remains false indefinitely
• Post-changes
  • Console output from within token.onCancellationRequested
  • token.isCancellationRequested changes based on button press

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

Signed-off-by: Matthew Langley [email protected]

[colin-grant-work]

Thanks for the contribution, @matt-dot! I believe this is working well. The extraneous TASKS_MAIN should be removed (I think), and it would be helpful to update the testing instructions:

Add a console.log checking the value of token.isCancellationRequested

Add a console.log where? In my testing it, I added it to the setTimeout callbacks here, but the instructions should provide more detail.

Run and press the cancel button contained in the notification

Run what? I assume the extension's 'Show Progress' command.

[matt-dot]

Yes your assumptions are correct and I have amended the instructions. I'll be sure to be more detailed and specific in the future 👍

[colin-grant-work]

LGTM, thanks for the contribution!