| 7 Feb 2026 |
 alexfmpe | is haskell.packages.ghc912.foobarpackage not cached in hydra? | 19:40:59 |
 andromeda | it rebuilt linear, opengl, glfw-b, and most/all of their dependencies, so I guess not | 19:44:29 |
| andromeda | new favourite language extension MultilineStrings | 19:48:36 |
| alexfmpe | $ nix-build -A haskell.packages.ghc912.haskell-language-server --dry-run 2>&1 | grep "will be"
these 472 paths will be fetched (354.11 MiB download, 4469.75 MiB unpacked):
| 19:49:52 |
| alexfmpe | seems cached for x86_64-linux at least | 19:49:59 |
| alexfmpe | $ nix-build -A haskell.packages.ghc912.linear --dry-run 2>&1 | head -n 10
these 2 derivations will be built:
/nix/store/k43nhxkm1wssqw6dcypgq911bjskchfd-bytes-0.17.5.drv
/nix/store/49f28h8fg1bbf8mdgf2wpnv84r2jhp1y-linear-1.23.3.drv
these 81 paths will be fetched (31.83 MiB download, 402.85 MiB unpacked):
| 19:51:52 |
| alexfmpe | maybe you happened to build something recently merged so hydra hadn't catched up yet | 19:52:28 |
| andromeda | 🤷♀️ | 19:53:49 |
 Alex | It's inconsistent because haskell-updates gets all non-broken packages for its default GHC cached, but sometimes master (and thus nixpkgs-unstable) deviates slightly from it. | 20:15:47 |
| alexfmpe | ah fair, I was checking in haskell-updates | 20:17:53 |
| alexfmpe | seems pretty much the same in current master:
$ nix-build -A haskell.packages.ghc912.haskell-language-server --dry-run 2>&1 | grep "will be"
these 507 paths will be fetched (357.33 MiB download, 4501.69 MiB unpacked):
$ nix-build -A haskell.packages.ghc912.linear --dry-run 2>&1 | head -n 4
these 2 derivations will be built:
/nix/store/57bmq5jy0sraqqava0jr0swivma0xd0q-bytes-0.17.4.drv
/nix/store/pbghk5rsl6s077p32m655yvn8c8fc246-linear-1.23.2.drv
these 100 paths will be fetched (36.87 MiB download, 465.34 MiB unpacked):
| 20:18:59 |
| 8 Feb 2026 |
 sterni | we've removed 9.12.1, so must be an old revision | 11:52:55 |
 chreekat | If I try to override Cabal and Cabal-syntax in a package set, why do I end up with multiple versions of Cabal? In particular I get this serious warning:
Warning:
This package indirectly depends on multiple versions of the same package. This is very likely to cause a compile failure.
package hackage-security (hackage-security-0.6.2.4-7CLHB9zPIN0FxCfhihIq1r) requires Cabal-syntax-3.10.3.0
package Cabal (Cabal-3.12.1.0-HdYCe711lcf3vEdSKCpUQK) requires Cabal-syntax-3.12.1.0-JlhyVgsDFbHIDMshThsYz
Is it because those packages are not overridable (boot packages or such)? Or could it be configure-time dependencies?
| 12:28:56 |
| chreekat | Am I right in assuming that usually if you override a package in a package set (examples from the file I'm modifying: https://github.com/commercialhaskell/stackage-server/blob/master/package.nix), the override you specify becomes the only version of that package available, regardless of where it lives in the dependency tree of other packages in the set? | 12:31:10 |
| sterni | This is true, but the core packages bundled on GHC still depend on other core packages. So if you want to globally override Cabal, you also need to globally override all core packages that (indirectly) depend on Cabal, so they get rebuilt. | 12:32:18 |
| sterni | Then you also need to convince the cabal solver to pick those packages over the core packages which can sometimes be tricky (but usually just works). | 12:32:44 |
| sterni | in this case the latter seems to be happening, i.e. hackage-security is still built against the core package | 12:33:37 |
| chreekat | Ok, so my memory/intuition was fairly correct. How can I do a "null" override for hackage-security and any other packages, so they get rebuilt? certainly not just hackage-security = old.hackage-security, ... | 12:36:19 |
| sterni | should be rebuild as it has a Cabal input. Check what version it is and what constraints it has on Cabal. Maybe it just doesn't allow 3.12. | 12:39:34 |
| chreekat | cool, things seem to be progressing by setting jailbreak = true for the package. Oh, what terrors may await | 12:43:33 |
| chreekat | (I thought about just bumping the nixpkgs pin to pick up a newer version of Cabal, but since this particular project is upstream of the snapshots that are upstream of nixpkgs packages I thought it would be good to ensure I can independently upgrade Cabal to pick up packages that use newer versions) | 12:44:39 |
| chreekat | damn, that changed the hash and rebuilt some stuff, but it did not get any further | 12:45:35 |
| sterni | you can try passing --constraint=Cabal>=3.12 as a configure flag | 12:46:33 |
| chreekat | ooh, neat, searching for a flag like that found some good examples of massaging dependencies on Cabal | 12:48:47 |
| chreekat | This did a thing, but it created an impossible condition by adding && Cabal>=3.12 to every existing branch of the constraint on Cabal :)
Error: Setup: Encountered missing or private dependencies:
Cabal ((>=1.14 && <1.26 || >=2.0 && <2.6 || >=3.0 && <3.7) && >=3.12) &&
(>=1.14 && <1.26 || >=2.0 && <2.6 || >=3.0 && <3.7) && >=3.12 || (>=3.7 &&
<3.12) && >=3.12,
| 12:58:37 |
| sterni | ah right the constraints are behind a conditional, so jailbreak won't relax them. | 13:00:23 |
| sterni | you need to either patch that or more likely upgrade to a version of hackage-security that does support Cabal 3.12 since I doubt it will build even if you patch the cabal file | 13:00:58 |
| chreekat | ok, i'll fall back to just bumping the nixpkgs pin for now | 13:01:26 |
| chreekat | thanks for the help! | 13:03:26 |
| sterni | wonder when one of those cabal install plan to nix generator projects finally pans out. Should be very possible to make one. I think those would be pretty useful, or alternatively ig revive something like stackage2nix | 13:07:27 |
