Ability to add task subschema

[RomanNikitenko]

What it does

At the moment default schema and schemes of customized detected tasks are registered, so only these tasks are available for running.

The PR provides ability to add task subschema from an extension for a custom task type to get ability run it from Terminal => Run Task menu.

How to test

Please use my forked repo for testing, it contains:

• the current PR changes
• the test extension which allows to add/remove schemes for custom types
• tasks with custom type for testing

1. git clone https://github.com/RomanNikitenko/theia.git
2. cd theia/ and git checkout task-extension.
3. Build the project and run it.
4. The project contains prepared tasks in tasks.json file, so please open the cloned project: File=>Open... and select the project.
5. Go to Terminal => Run Task menu:
   you can see that only SHELL task is available for running
6. Go to Help menu and select Add CHE task schema
   you can see that now CHE task is available for running as well as SHELL task.
7. Try the same for EXEC task
8. You can try to remove subschema for CHE task and EXEC task using Help menu
   you can see that the corresponding tasks are not available for running after that.

Please see https://youtu.be/VOuFi9M2Q2k

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: Roman Nikitenko [email protected]

[akosyakov]

@elaihau please finish the review

[elaihau]

I tested with Roman's extension, and confirm both "add schema" and "remove schema" work.

[RomanNikitenko]

@akosyakov
could you review - is it OK from your point of view?
thank you!

[akosyakov]

code-wise looks good, thank you!