I don't think this is backwards compatible like this, because previously deluge wasn't passed the -c option, in which case in uses the config file at the default location, which is ~/.config/deluge/core.conf. So by now generating it in NixOS and passing it via -c means everyone's configuration will be reset to the default specified here.

I changed it to the current config default location /var/lib/deluge/.config/deluge, similar to how it is done in the transmission service.

That will just override the users stateful configuration with the one generated by NixOS which is even worse :)

You need to handle the case of users having either stateful or declarative configs. There's multiple ways of doing this:

• Add a NixOS option services.deluge.declarative, defaulting to false, which tells the module whether it should be declarative or stateful.
• Only write the declarative file if there's no file there already (or if .declarative exists), and in that case do touch .declarative, indicating that it uses the declarative file. Otherwise output a warning "Warning: Can't use declarative NixOS configuration, stateful configuration already exists at ".

I personally prefer the first one. If you have other ways to solve this, that would work too of course.

I modify the PR to add services.deluge.declarative as you asked, I took inspiration from your commit 58c89ec. Is there anything else missing for it to be merged?

@infinisil I think I have made all the modification needed. Can you please review this PR one last time?

@infinisil I have take into account all of your review and kept closed the problematic ports we discussed of. I hope this time it can be merged.

@infinisil Hopefully this is the last time I bother you with this PR.

@GrahamcOfBorg test deluge

Looking good, thanks for your patience :)

@GrahamcOfBorg test deluge