Make setup-wsl idempotent so it can be used on custom runners

[ssbarnea]

At this moment, each time setup-wsl runs, it will try to reinstall wsl, and that has huge performance drawbacks.

It would be better if it could have a mode where it would reconfigure it only if needed. Running it twice should have no effects.

Even more interesting is that running it a pre-configured machine destroyed my github runner because I installed it inside the wsl, this being an important performance hack for the very slow WSL. Basically I had a symlink from C:\actions-runner > \\wsl.localhost\ubuntu\home\runner\action-runner.

When the action run,.... removed the already existing WSL installation, which included the runner itself. :D

I tried to add sanity check before calling the action that looked like:

      - name: Determine if we have a working WSL
        id: wsl_check
        shell: cmd
        run: wsl cat /etc/os-release
        continue-on-error: true

      # https://github.com/marketplace/actions/setup-wsl
      - name: Activate WSL
        if: steps.wsl_check.outcome == 'failure'
        uses: Vampire/[email protected]

The problem is that I soon discovered that I NEED to run the action all the time in order to be able to benefit from its ability to change the default shell to use wsl.

I don't know how to only make use of this part of it.

[Vampire]

I'm not entirely sure what you mean.
Which part destroys what?
The action should only do things that are necessary and indeed running it a second time should not do much.
The "Install WSL" step if you meant that for example is guarded by doing wsl --status and only being executed if the output contains "is not installed".

[ssbarnea]

You are right, apparently it is idempotent. Not sure why I got the impression that it is not.