I've had some success with it if I'm giving it small tasks and describe in as much detail as possible. By design (from what I gather) it can only work on stuff it was able to use in training, which means the language needs to be documented extensively for it to work.

Stuff like Wordpress or MediaWiki code it does generally good at, actually helped me make the modules and templates I needed on mediawiki, but for both of those there's like a decade of forum posts, documentation, papers and other material that it could train with. Fun fact: in one specific problem (using a mediawiki template to display a different message whether you are logged in or not), it systematically gives me the same answer no matter how I ask. It's only after enough probing that GPT tells me because of cache issues, this is not possible lol. I figure someone must have asked about this same template somewhere and it's the only thing it can work off of from its training set to answer that question.

I also always double-check the code it gives me for any error or things that don't exist.