Jade Lovelace
01ff67595b
This is not ca-derivations. We don't care about self-references or any of the rewriting or stuff like that; if you want something like that, write your user code so it figures out where it is. The reason I want to do this is for integrating other build systems with Lix: if you're importing something built *outside the store* with a non-Nix build system, it makes no sense to put it in an input-addressed path since it's not possible to come up with a derivation for it. But you need *some* hash, so the output hashing is the most sensible option. It is also nice because of not needing trusted user privileges to import it, since the hash describes the exact contents of the output path. We use this feature (implemented externally to Lix; this CL eliminates that step) at Mercury to integrate buck2 with Nix on the output side: we import things to the Nix store as ca paths with references. These can then be consumed by Nix language with: ``` # Hack from https://git.lix.systems/lix-project/lix/issues/402#issuecomment-5889 path: builtins.appendContext path { ${path} = { path = true; }; } ``` Test plan: ``` $ nix store add-path --references-list xx-refs-list ./README.md /nix/store/szcwnm13d9gmxx8fly0bz82l42jgysw6-README.md $ cat xx-refs-list /nix/store/g9hhwjbkdrw0wnbd3axfs4icyb37nr6b-bash-interactive-5.3p3 $ nix path-info --json /nix/store/szcwnm13d9gmxx8fly0bz82l42jgysw6-README.md | jq . [ { "ca": "fixed:r:sha256:1pj59fy7zcrn949ry9kgv4ba17h2sy3z2is469abj912cvbl14n3", "narHash": "sha256-w5JA12YiJLlUMkRH8YfXAp6gFtlvJp8TSTazf7xLRd4=", "narSize": 1384, "path": "/nix/store/szcwnm13d9gmxx8fly0bz82l42jgysw6-README.md", "references": [ "/nix/store/g9hhwjbkdrw0wnbd3axfs4icyb37nr6b-bash-interactive-5.3p3" ], "registrationTime": 1771266146, "valid": true } ] ``` Change-Id: I005a03003dfc24108e018e599dbe0b5d6a6a6964
1.3 KiB
synopsis, cls, category, credits
| synopsis | cls | category | credits | ||
|---|---|---|---|---|---|
| nix store add-path now supports references |
|
Features |
|
Lix supports two categories of hashes in store paths: input-addressed and output-addressed.
Currently, in Nix language, there is no way to produce output-addressed paths with references, as fixed-output derivations forbid references. However, the Nix store actually supports references in output-addressed paths. This is very useful for importing build products created outside of Lix that reference dependency store paths since such build products have no associated derivation so don't make any sense to input-address. Previously, output-addressed paths with references could only be created by writing a custom client to the rather-baroque Nix daemon protocol; now it's available in the CLI.
Using nix store add-path --references-list-json REFS_LIST_FILE SOME_PATH with a JSON list of string store paths, you can now create such paths with the Lix CLI.
They may be consumed from Nix language using something like builtins.storePath or the following which also works in pure evaluation mode:
# Hack from https://git.lix.systems/lix-project/lix/issues/402#issuecomment-5889
path:
builtins.appendContext path {
${path} = {
path = true;
};
}