ERROR: The themes directory is either empty or doesn’t exist. Please check your installation.

[pathawks]

In multi-site mode, if there are no themes enabled for a particular site and no network enabled themes, that site's dashboard will report the error

ERROR: The themes directory is either empty or doesn’t exist. Please check your installation.

Ov course, this isn't entirely accurate. The themes directory may not be empty, but the problem is that no themes are enabled. The wording should probably be updated to reflect this.

[pathawks]

I was mistaken regarding the root of the problem.

I was getting the error message because I deleted twentyeleven, which was selected as the theme of the site in question.
So the problem wasn't that there were no themes in the themes directory, but that the selected theme no longer existed.

I still think the wording could be made a bit more clear.

[SergeyBiryukov]

Related: #21931

[johnbillion]

I've just patched this up and I was about to add a new ticket and then found this one.

My attached patch displays the error message from the WP_Error object similarly to Sergey's patch, and additionally displays the error on the Appearance screen, hides the various theme metadata and customize controls there if there's an error, and improves the error message for theme_not_found.

Note that my patch looks like it does a lot but in fact it's just an extra tab indent for the most part. Best viewed without whitespace changes.

[johnbillion]

Before screenshot

[johnbillion]

After screenshot

[nacin]

21670.2.diff​ only suppresses the rest of the current theme information on themes.php if the error is fatal in nature. (I've thought about introducing levels or groups of errors here, but haven't.) Basically: If something is wrong with the parent theme, or if index.php is missing, most things still work. (All other errors have to do with style.css being unreadable or missing.)

[nacin]

Uses double quotes around %s in the new error message.

[nacin]

In 25666:

Show a proper error message on the dashboard when the current theme is broken.

Clean up Appearance -> Themes when we don't have enough information to show for a broken theme.

Clean up broken/ugly "alt" row styling when we are displaying broken themes.

props johnbillion for initial patch.
fixes #21670.