fix: customCSS catch and throw error

[Its-Just-Nans]

Related to #3554

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[delucis]

Thanks for the PR @Its-Just-Nans! I actually think we can avoid this code change and instead check it ourselves in the Starlight configuration schema would be my guess. We have access there to the public directory name, so could easily check for values in the customCss array that start with the public directory. That way we avoid hitting the Astro error altogether.

[delucis]

Thanks again for the PR @Its-Just-Nans!

I just took the time to update it to run the validation alongside all our other user config validation logic and throw a clear error explaining how to resolve the issue.

[Its-Just-Nans]

Thanks again for the PR @Its-Just-Nans!

I just took the time to update it to run the validation alongside all our other user config validation logic and throw a clear error explaining how to resolve the issue.

Thanks to you for all your work.

Just a little question, the goal was also to help the user by saying "you can add css using the head configuration of starlight". Why not adding that part?

Thanks you

[delucis]

Why not adding that part?

That’s not the best approach: you really should use src/ and let Starlight bundle CSS for you as it improves the site performance in various ways.

Of course, using head is still possible in the few circumstances where public/ is really needed, but in an error message like this we need to provide clear advice that’s as simple as possible to point users to what is the right choice in most cases so that they can resolve the error quickly.