While the APIs that are being used for ${program}.withPackages pattern is very nice and egronomic, it does have a downside of not using a spliced package. So for example recently I needed Python with a package in nativeBuildInputs, but then when cross-compiled it only has Python from pkgsHostTarget, leading to an invalid executable being used at build time and then either manually using pkgsBuildBuild.python or using the spliced Python and package separately.

I wonder if there is a good way to solve this? Meaning a way to use the spliced package, as for folks not in the know of splicing it is probably confusing to see a package operate differently based upon whether you use the helpers or not. But many of these helpers are implemented with finalAttrs.finalPackage, which isn't spliced.

• https://github.com/NixOS/nixpkgs/pull/451665
• https://github.com/NixOS/nixpkgs/pull/451147
• https://github.com/NixOS/nixpkgs/pull/447166
• https://github.com/NixOS/nixpkgs/pull/445833

ElvishJerricco:

❯ /nix/store/d5xywf1k4cmmr2jlxmsc5qa6zcwn3myd-nixos-vm/bin/run-nixos-vm -nographic
[    0.582586] (udev-worker)[90]: mtd0ro: Failed to find and pin callout binary "/nix/store/p9vl1dd3qjafk36wsb49q79a2rhjrpbi-systemd-258/lib/udev/mtd_probe": No such file or directory
[    0.880121] (udev-worker)[94]: hidraw0: Failed to find and pin callout binary "/nix/store/p9vl1dd3qjafk36wsb49q79a2rhjrpbi-systemd-258/lib/udev/fido_id": No such file or directory
[    0.886137] (udev-worker)[97]: hidraw1: Failed to find and pin callout binary "/nix/store/p9vl1dd3qjafk36wsb49q79a2rhjrpbi-systemd-258/lib/udev/fido_id": No such file or directory
[    3.416831] systemd[1]: Failed to preset unit: Unit autovt@.service does not exist

user: matthew nixos-musl on  refactor [!] 
✦ ❯ nix path-info -Sh `readlink ./result`
/nix/store/gzv6h1zjghv7mph64wwfzcqvywmhqfpz-nixos-system-nixos-25.11.20251015.ac6f169	444.6 MiB

user: matthew nixos-musl on  refactor [!] 
✦ ❯ nix build .#nixosConfigurations.gnu-musl-llvm.config.system.build.toplevel --keep-going 
warning: Git tree '/home/matthew/git/nixos-musl' is dirty
evaluation warning: system.stateVersion is not set, defaulting to 25.11. Read why this matters on https://nixos.org/manual/nixos/stable/options.html#opt-system.stateVersion.
Finished at 22:26:13 after 3s

user: matthew nixos-musl on  refactor [!] took 3s 
✦ ❯ nix path-info -Sh `readlink ./result`
/nix/store/29ic0hjnydm8w7g172jfz72484bwd75s-nixos-system-nixos-25.11.20251015.ac6f169	413.7 MiB

DBI-aarch64-linux> /nix/store/bvp4jwn1ibkjh7yhr2mlcxxd908y4x4v-perl-5.40.0/lib/perl5/5.40.0/aarch64-linux-thread-multi/CORE/perl.h:3358:22: error: unknown type name 'off64_t'; did you mean 'off_t'?
DBI-aarch64-linux>  3358 | #       define Off_t off64_t
DBI-aarch64-linux>       |                      ^~~~~~~
DBI-aarch64-linux> /nix/store/bvp4jwn1ibkjh7yhr2mlcxxd908y4x4v-perl-5.40.0/lib/perl5/5.40.0/aarch64-linux-thread-multi/CORE/perlio.h:252:15: note: in expansion of macro 'Off_t'
DBI-aarch64-linux>   252 | PERL_CALLCONV Off_t PerlIO_tell(PerlIO *);

FAILED: [code=1] libnixutil.so.p/unix_file-descriptor.cc.o 
aarch64-unknown-linux-musl-clang++ -Ilibnixutil.so.p -I. -I.. -Iinclude -I../include -I../widecharwidth -Ilinux/include -I../linux/include -Iunix -I../unix -Iunix/include -I../unix/include -I/nix/store/2kq21fj8mcqbb2dk078kdkz0a4slp9y9-libarchive-aarch64-unknown-linux-musl-3.8.1-dev/include -I/nix/store/15nrd5ki3mn2wky0879jq6p8v3nl3ins-nlohmann_json-aarch64-unknown-linux-musl-3.12.>
../unix/file-descriptor.cc:174:20: error: use of undeclared identifier 'SYS_close_range'; did you mean 'unix_close_range'?
  174 |     return syscall(SYS_close_range, first, last, (unsigned int) flags);
      |                    ^~~~~~~~~~~~~~~
      |                    unix_close_range
../unix/file-descriptor.cc:171:12: note: 'unix_close_range' declared here
  171 | static int unix_close_range(unsigned int first, unsigned int last, int flags)
      |            ^
../unix/file-descriptor.cc:174:12: error: no matching function for call to 'syscall'
  174 |     return syscall(SYS_close_range, first, last, (unsigned int) flags);
      |            ^~~~~~~
/nix/store/4w3bhgsi1al9v1jwgk9vc6ch20l7ynba-musl-aarch64-unknown-linux-musl-1.2.5-dev/include/unistd.h:180:6: note: candidate function not viable: no known conversion from 'int (unsigned int, unsigned int, int)' to 'long' for 1st argument
  180 | long syscall(long, ...);
      |      ^       ~~~~
2 errors generated.