This may need an entry in the release notes for NixOS 18.03 (backward incompatibility).

Okay, added release note.

Is @qknight the right maintainer to nudge?

@uwap could you have a look at this please?

Looks alright to me!

@bjornfor shall we also integrate it into 17.09?

@qknight: Won't that break some users configs? Can it be considered a bugfix? I don't know :-)

I would vote for calling this a bugfix, since the inconsistency I described in #30521 is pretty clearly buggy IMO. Looking at the list of supported options, I don't actually think there are any list-of-string options that could reasonably want a literal dollar sign in them—networks and domain names can't contain them—so unless I'm missing something, someone would have to be doing some weird stuff if this broke their config.

Undo the 18.03 release note then then, and pick both commits to release-17.09?

+1 to get this into a bugfix earlier than 18.03, as it currently stands, this just straight-up breaks postfix for most configurations. I'm just a user but wanted to mention that this caused postfix to simply break upon upgrading to 17.09 (note that the service starts normally but parses incorrect destinations, so the failure is hard to catch operationally).

so any wish what we should do?