Don't clear the CSS cache when installing themes

Thank you for creating this issue to improve Drupal.

We are working to decide if this task is still relevant to a currently supported version of Drupal. There hasn't been any discussion here for over 8 years which suggests that this has either been implemented or is no longer relevant. Your thoughts on this will allow a decision to be made.

Since we need more information to move forward with this issue, the status is now Postponed (maintainer needs more info). If we don't receive additional information to help with the issue, it may be closed after three months.

Thanks!

    $this->cssCollectionOptimizer->deleteAll();

This is still in the theme installer.

Needs the patch converted to an MR, or just a fresh MR created removing that line. Not sure we need tests for this, we'd just be testing that we removed the code really - e.g. we'd need to get some CSS aggregates created on disk, install a theme, make sure they're still there. But also with 📌 Bring back the asset stale file threshold Active new aggregates wouldn't get deleted anyway, making this impossible to test. Given that, removing the needs tests tag.

I will convert the patch to MR.

Just an FYI newly tagged novice tickets are typically meant for newer users to try, that have less then 1 page of posts.

After a few weeks if no new user doesn't pick it up it's fair game.

Thank you, for highlighting this @smustgrave.

No worries!

For good practice lets update the summary to use the standard template

Updated issue summary.