@NorfairKing Thank you for the apology. I admit I wasn’t really motivated to answer to your first message.
I admit pinning nixpkgs to get a fix stackage-lts is a use case that I know about, (I even helped people using it) but I had kinda forgotten about it, because it is philosophically quite a different approach to how I develop my projects.
So it’s good to have this feedback. It’s of course a bit hard to tell how widespread this usecase is, but we should keep it in mind for future considerations.
Anyways I think if I needed to figure out what to do to develop a project that works friction free with nix and with stack I guess pinning a nixpkgs and the matching nightly snapshot would be the way to go now. Sometimes nightly wont be in a good state I guess, but in that time you just don‘t bump the pinning of both. (btw. right now nightly even contains more packages than LTS.)
To reiterate: Our aim was to increase the number of working packages in nixpkgs. That includes btw. stackage packages, which can sometimes need manual intervention even though they are in stackage.
Our impression was: If we can provide a larger, more modern set of working packages, users will profit from that. (An example were btw. all hs-gtk dependent packages, which were nearly unsupportable because nixpkgs master used newer system libraries then stackage LTS needed. One example for how nightly seems to be a better fit in nixpkgs.)
Regarding reverting this change: Yeah, we could, but it would break packages and throw away a lot of work and cause quite a lot of new work. Also as domen pointed out, it would mean version downgrades, which sounds quite ugly. I personally am open to discuss if this is a good permanent solution, but let’s try to flow with it for a while. We’ll collect maintenance experience and I guess in a few months we’ll see how this works out.
The fact that 8.10.2 has serious issues that affect our users is sad, but a little bit independent from the question of the stackage snapshot. (I doubt that this issue is the reason that there is no LTS release with 8.10.2). After all we had tested 8.10.x quite extensively in the last months and we run test-suites for a good part of hackage on hydra, which didn‘t surface serious issues. So the only thing wrong with switching to 8.10.2 in my impression is that it’s “too new for all bugs to surface”, but I feel like for that use case we have the stable branches? (We wouldn‘t have done this switch shortly before branch-off.)
I hope I don‘t sound to defensive here. Of course any change of this kind means friction. Let’s see if it was worth it. Having this discussions tells me what to be mindful of in the future.