Fail to built `unix` package from stackage on GHC 9.10 and 9.12 snapshots

[chaserhkj]

Describe the bug

I am working on nix integration with BNFC through haskell.nix, but build on GHC 9.10 and 9.12 branch seems to fail with dependency unix failing to build.

• Build system: x86_64-linux
• GHC version: 9.10.2/9.12.2
• Haskell.nix version (or commit) used: Master branch as of now (f7b3cfe)

Steps To Reproduce

GHC 9.10, targeting stack snapshot lts-24.1

hkj@hkj-comphost:~$ nix-build -E '(with import <nixpkgs> (import <haskell.nix> {}).nixpkgsArgs; haskell-nix.snapshots."lts-24.1").unix.components.library'
this derivation will be built:
  /nix/store/s62kiqvx26jpmqbvvjm54w0liadpvymq-unix-lib-unix-2.8.6.0.drv
building '/nix/store/s62kiqvx26jpmqbvvjm54w0liadpvymq-unix-lib-unix-2.8.6.0.drv'...
Running phase: unpackPhase
unpacking source archive /nix/store/62g3lmhwy1bp1vi8x5dl0iczfxzr7382-unix-2.8.6.0.tar.gz
source root is unix-2.8.6.0
setting SOURCE_DATE_EPOCH to timestamp 1000000000 of file "unix-2.8.6.0/unix.cabal"
Running phase: patchPhase
'/tmp/nix-build-unix-lib-unix-2.8.6.0.drv-0/.attr-0h9ydb7s8pfhl5kfs3rmmwnmpi49yyiw7jgr5dpw9rmvv8sy0f2b' -> 'unix.cabal'
Running phase: updateAutotoolsGnuConfigScriptsPhase
Updating Autotools / GNU config script to a newer upstream version: ./config.sub
Updating Autotools / GNU config script to a newer upstream version: ./config.guess
Running phase: configurePhase
Configure flags:
--prefix=/nix/store/yxnkc99gpkk49365a25296nqnw6pqiqq-unix-lib-unix-2.8.6.0 lib:unix --package-db=clear --package-db=/tmp/nix-build-unix-lib-unix-2.8.6.0.drv-0/tmp.tHwg0J9zr9/lib/ghc-9.10.2/lib/package.conf.d --flags=-os-string --with-ghc=ghc --with-ghc-pkg=ghc-pkg --with-hsc2hs=hsc2hs --with-gcc=cc --with-ar=ar --with-strip=strip --with-ld=ld --disable-executable-stripping --disable-library-stripping --disable-library-profiling --disable-profiling --enable-static --enable-shared --disable-executable-dynamic --disable-coverage --enable-library-for-ghci --datadir=/nix/store/f5sfz657c0lf7207bmapcy4209ds7xkr-unix-lib-unix-2.8.6.0-data/share/ghc-9.10.2 --enable-split-sections
Configuring library for unix-2.8.6.0...
Error: [Cabal-8010]
Encountered missing or private dependencies:
    filepath >=1.4.100.0 && <1.5.0.0

error: builder for '/nix/store/s62kiqvx26jpmqbvvjm54w0liadpvymq-unix-lib-unix-2.8.6.0.drv' failed with exit code 1

GHC 9.12, targeting stack snapshot nightly-2025-07-23

hkj@hkj-comphost:~$ nix-build -E '(with import <nixpkgs> (import <haskell.nix> {}).nixpkgsArgs; haskell-nix.snapshots."nightly-2025-07-23").unix.components.library'
this derivation will be built:
  /nix/store/jlgklrh1pk2wpw12dji1fkr9c3rr0jyq-unix-lib-unix-2.8.6.0.drv
building '/nix/store/jlgklrh1pk2wpw12dji1fkr9c3rr0jyq-unix-lib-unix-2.8.6.0.drv'...
Running phase: unpackPhase
unpacking source archive /nix/store/62g3lmhwy1bp1vi8x5dl0iczfxzr7382-unix-2.8.6.0.tar.gz
source root is unix-2.8.6.0
setting SOURCE_DATE_EPOCH to timestamp 1000000000 of file "unix-2.8.6.0/unix.cabal"
Running phase: patchPhase
'/tmp/nix-build-unix-lib-unix-2.8.6.0.drv-0/.attr-0h9ydb7s8pfhl5kfs3rmmwnmpi49yyiw7jgr5dpw9rmvv8sy0f2b' -> 'unix.cabal'
Running phase: updateAutotoolsGnuConfigScriptsPhase
Updating Autotools / GNU config script to a newer upstream version: ./config.sub
Updating Autotools / GNU config script to a newer upstream version: ./config.guess
Running phase: configurePhase
Configure flags:
--prefix=/nix/store/7xwwxn7dscw5jk90kc5p6afy8jypwmbk-unix-lib-unix-2.8.6.0 lib:unix --package-db=clear --package-db=/tmp/nix-build-unix-lib-unix-2.8.6.0.drv-0/tmp.YcuM8JmPSR/lib/ghc-9.12.2/lib/package.conf.d --flags=-os-string --with-ghc=ghc --with-ghc-pkg=ghc-pkg --with-hsc2hs=hsc2hs --with-gcc=cc --with-ar=ar --with-strip=strip --with-ld=ld --disable-executable-stripping --disable-library-stripping --disable-library-profiling --disable-profiling --enable-static --enable-shared --disable-executable-dynamic --disable-coverage --enable-library-for-ghci --datadir=/nix/store/jjr3hx078xnz9gq7b6dps6lmx4agmy7y-unix-lib-unix-2.8.6.0-data/share/ghc-9.12.2 --enable-split-sections
Configuring library for unix-2.8.6.0...
Error: [Cabal-8010]
Encountered missing or private dependencies:
    filepath >=1.4.100.0 && <1.5.0.0

error: builder for '/nix/store/jlgklrh1pk2wpw12dji1fkr9c3rr0jyq-unix-lib-unix-2.8.6.0.drv' failed with exit code 1

Additional context

BNFC CI does stack builds and 9.10/9.12 branches seem to be doing fine so I suppose this is a problem with haskell.nix rather then the stackage version. But I did not do the stack build tests myself so correct me if I am wrong.

[andreasabel]

Background:

Encountered missing or private dependencies:
filepath >=1.4.100.0 && <1.5.0.0

Stackage has moved to filepath-1.5.4.0 for the GHC 9.10 and 9.12 snapshots.
This version is also what unix-2.8.6.0 is build against there.

[rimmington]

unix-2.8.6.0 and filepath-1.5.4.0 are also the versions that GHC 9.10.2 ships with.

Unfortunately haskell.nix builds unix 2.8.6.0 with the wrong flags: -os-string instead of the +os-string required to use unix with the newer filepath dependency.

building '/nix/store/v3hvs69klxmv85xpq4ii3b4lxfy74z86-unix-lib-unix-2.8.6.0.drv'...
Running phase: unpackPhase
unpacking source archive /nix/store/62g3lmhwy1bp1vi8x5dl0iczfxzr7382-unix-2.8.6.0.tar.gz
source root is unix-2.8.6.0
setting SOURCE_DATE_EPOCH to timestamp 1000000000 of file "unix-2.8.6.0/unix.cabal"
Running phase: patchPhase
'/build/.attr-0h9ydb7s8pfhl5kfs3rmmwnmpi49yyiw7jgr5dpw9rmvv8sy0f2b' -> 'unix.cabal'
Running phase: updateAutotoolsGnuConfigScriptsPhase
Updating Autotools / GNU config script to a newer upstream version: ./config.sub
Updating Autotools / GNU config script to a newer upstream version: ./config.guess
Running phase: configurePhase
Configure flags:
--prefix=/nix/store/mbms7irx56z9wc11n9q7sbskrl5x9hc3-unix-lib-unix-2.8.6.0 lib:unix --package-db=clear --package-db=/build/tmp.ceDnDuNBWi/lib/ghc-9.10.2/lib/package.conf.d --flags=-os-string --exact-configuration --dependency=bytestring=bytestring-0.12.2.0-8VwC1WW0scVJhY9zkMPLSo --dependency=filepath=filepath-1.5.4.0-7ox7Gkv1YtrIHx2ZOEekCh --dependency=exceptions=exceptions-0.10.9-7GfBIDlmIjfGdMpqfpFvXB --dependency=mtl=mtl-2.3.1-IeekFE2olK8S05ho2UQHR --dependency=transformers=transformers-0.6.1.1-AbhC9SWeDLiFqjfQeCp9xm --dependency=stm=stm-2.5.3.1-1zRAaIkzunn182DE9OgkAR --dependency=os-string=os-string-2.0.4-5dr0RWeM07VADDIENbMuJr --dependency=time=time-1.12.2-D72o1bgJd3zKtQRywshk2Z --dependency=array=array-0.5.8.0-inplace --dependency=base=base-4.20.1.0-inplace --dependency=deepseq=deepseq-1.5.0.0-inplace --dependency=ghc-bignum=ghc-bignum-1.3-inplace --dependency=ghc-boot-th=ghc-boot-th-9.10.2-inplace --dependency=ghc-internal=ghc-internal-9.1002.0-inplace --dependency=ghc-prim=ghc-prim-0.12.0-inplace --dependency=integer-gmp=integer-gmp-1.1-inplace --dependency=pretty=pretty-1.1.3.6-inplace --dependency=rts=rts-1.0.2 --dependency=system-cxx-std-lib=system-cxx-std-lib-1.0 --dependency=template-haskell=template-haskell-2.22.0.0-inplace --with-ghc=ghc --with-ghc-pkg=ghc-pkg --with-hsc2hs=hsc2hs --with-gcc=cc --with-ar=ar --with-strip=strip --with-ld=ld --disable-executable-stripping --disable-library-stripping --disable-library-profiling --disable-profiling --enable-static --enable-shared --disable-executable-dynamic --disable-coverage --enable-library-for-ghci --datadir=/nix/store/82l0hdrpmbrgv653fswg24j0pspnf4p2-unix-lib-unix-2.8.6.0-data/share/ghc-9.10.2 --enable-split-sections 
Configuring library for unix-2.8.6.0...

...

[11 of 53] Compiling System.Posix.Env.PosixString ( dist/build/System/Posix/Env/PosixString.hs, dist/build/System/Posix/Env/PosixString.o, dist/build/System/Posix/Env/PosixString.dyn_o )
System/Posix/Env/PosixString.hsc:45:1: error: [GHC-87110]
    Could not load module ‘System.OsString.Internal.Types’.
    It is a member of the hidden package ‘os-string-2.0.4’.
    Perhaps you need to add ‘os-string’ to the build-depends in your .cabal file.
    Use -v to see a list of the files searched for.
   |
45 | import System.OsString.Internal.Types
   | ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^

System/Posix/Env/PosixString.hsc:47:1: error: [GHC-61948]
    Could not find module ‘System.OsString.Data.ByteString.Short’.
    Perhaps you meant
      System.OsString.Data.ByteString.Short (needs flag -package-id os-string-2.0.4)
      System.OsString.Data.ByteString.Short.Word16 (needs flag -package-id os-string-2.0.4)
      System.OsString.Data.ByteString.Short.Internal (needs flag -package-id os-string-2.0.4)
   |
47 | import qualified "os-string" System.OsString.Data.ByteString.Short as B
   | ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^

Same issue with directory-1.3.8.5 from Stackage LTS 24.2. Adding a new module to override the flags got those packages to build for my project:

modules = [
  {
    packages.directory.flags.os-string = true;
    packages.unix.flags.os-string = true;
  }
];