@Anthere this feature is live now, but I've noticed that it prevents any contributions happening if someone selects "wiki loves campaign" with categories of the wrong format.

Example on live: https://tools.wmflabs.org/isa/campaigns/7

The drop down is present, but with no options. It then tries to start a participate session with country=Null and finds no images.

We're currently adding some more detailed instructions and guidance on the CREATE campaign page to avoid the wrong selection from happening as much as possible. But it will of course happen, so we need to choose what to do when the country drop down does not find any options at all.

The simplest thing to do is to default back to "all images" mode if no options have been found (i.e. just ignore the dropdown and treat it as a 'non-WikiLoves' campaign).
But ideally we should check the syntax on the Create campaign page, and stop creation if the manager has made incorrect selections.

Any thoughts or preferences?

I'd say checking syntax and stoping creation if wrong selections might be the best...

I think that makes sense. I'll see if it's something I can setup relatively easily now.

If that works out well then we should leave fixing T231259: WLX campaign 7 is broken

That will be the only campaign we have set incorrectly and there shouldn't be a way to add an new ones after the change. Alex is the manager so we can ask him nicely to change his campaigns settings for the anomaly :)

New task created: T231302: Force correct WikiLoves category syntax

Awesome. Can you ask Alex then ?