Nadja Yang
fb169268a3
Rejecting an unwieldy originalist interpretation of the max_output_size
infrastructure mandate [1] — which, by checking NAR size pre-compression,
might be read to foreclose in-NAR densification — this commit resolves
the tension between binary cache availability and statutory size
discipline through equitable artifact pre-densification.
Specifically, we execute xz compression during the postInstall phase
of an intermediate derivation, coupled with a non-Hydra wrapper that
decompresses the payload transparently. This insulates end-users from
the underlying .tar.xz monolith while satisfying the strict procedural
requirements of the build farm's sensors.
We acknowledge reservations regarding the broader applicability of the
unorthodox pattern incepted herein.
See also Jakštys, commit msg. to bbd0655ae8 (2024) ("[intending]
to replace the `passthru.data-compressed` derivations that ha[d]
accumulated in nixpkgs with something more reusable"),
https://github.com/NixOS/nixpkgs/commit/bbd0655ae828b9f1cf39d891b52aa6506394ef46
Cf. Luna Nova, hipblaslt/default.nix ll. 113-114 (2026) (patching
hipblaslt C++ runtime to transparently decompress zstd-compressed
.dat files, as "required to keep [the] output under [H]ydra size
limit"), https://github.com/NixOS/nixpkgs/blob/fc1f8110e84b7a874826eee147170aee85082390/pkgs/development/rocm-modules/hipblaslt/default.nix#L113-L114
Cf. SuperSandro2000, Review of NixOS/nixpkgs#511524 (this PR) (2026)
("[w]hy not compress the well compressable [.olean] files in nix
with zstd?") (in dicta; a fortiori),
https://github.com/NixOS/nixpkgs/pull/511524#discussion_r3137725277
But cf. Yureka, gclient2nix.py ll. 162-167 (2025) (characterizing
recompression as "bypassing the size limit (making it count the
compressed instead of uncompressed size) rather than complying with
it"), https://github.com/NixOS/nixpkgs/blob/4dc9b83879ce51e180f37acb8e78ededdbf72798/pkgs/by-name/gc/gclient2nix/gclient2nix.py#L162-L167
[1] NixOS Infrastructure Cap., https://github.com/NixOS/infra/blob/170012a4682da0a130f6bc68caf3618743239783/build/hydra.nix#L116
Nixpkgs is a collection of over 120,000 software packages that can be installed with the Nix package manager. It also implements NixOS, a purely-functional Linux distribution.
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