lsix / hellohydra

Hydra test project

Hydra evaluation error

I am setting up an hydra server in house to run build and package our products. This repository provides a simple reproduction of the problem I encounter.

What I want to do

I am packaging an autotools based project. There is a line in the configure.ac that tells the tools what it the project name, what is the project version and who bugs should be sent to. It looks like:

AC_INIT([hellohydra], [0.1], [[e-mail]])

Somewhere in the nix-derivation function used to build this project, we should specify the name of the derivation and its version:

mkDrivation rec {
  name = "hellohydra-${version}";
  version = "0.1";
  …
}

Basically, I do wand to remove the repetition between those two files in order to only have one file to update when I release a new version.

Hacky solution

To do that, I have use a small python script wrapped in runCommand used to parse the configure.ac file and extract the version information I am looking for. It is done in the get_version.nix file. I then just have to call that function in my nix expression like this:

mkDrivation rec {
  name = "hellohydra-${version}";
  version = import ./get_version.nix { inherit pkgs; };
  …
}

Locally, it works perfectly. I can use a simple release.nix to describe what hydra would have to do and launch it:

$ NIX_PATH=nixpkgs=https://github.com/NixOS/nixpkgs-channels/archive/nixos-unstable.tar.gz:hellohydra=https://github.com/lsix/hellohydra/archive/master.tar.gz nix-build -A hellohydra release.nix
downloading ‘https://github.com/lsix/hellohydra/archive/master.tar.gz’... [0/0 KiB, 0.0 KiB/s]
unpacking ‘https://github.com/lsix/hellohydra/archive/master.tar.gz’...
downloading ‘https://github.com/NixOS/nixpkgs-channels/archive/nixos-unstable.tar.gz’... [0/0 KiB, 0.0  [10839/11102 KiB, 279.4 KiB/s]
…
/nix/store/z5k8r5kwhzwhqxqg2k54yfjn7agslhzz-hellohydra-0.1

Everything is great before I set foot on hydra…

Evaluating the jobset with hydra

Next step: create and evaluate the jobset in a hydra instance. The jobset creation is quite steight forward, here are the parameters I used:

param	value
…	…
Nix expression	release.nix in input hellohydra
…	…

Input name	Type	Values
hellohydra	Git checkout	https://github.com/lsix/hellohydra.git master
nixpkgs	Git checkout	https://github.com/NixOS/nixpkgs-channels.git nixos-unstable-small

When hydra evaluates the jobset, it gives me the following error:

in job ‘hellohydra’:
the string ‘hellohydra-0.1’ is not allowed to refer to a store path (such as ‘!out!/nix/store/ixiqwfgyiizvqfjqszs2hv09cvalq525-hellohydra_version.drv’)

Question

So yes, I fully understand that hydra-evaluator's job is definitevely not to instanciate the derivations. It planns everything and queues jobs. But for this kind of scenario, where I only rely on really small helper functions to actually fully describe my jobset, it would be apprecible to let the evaluator do this simple task (and it actually does it since it have correctly evaluated the derivation name).

Is there a way to acheive what I want to do?

I know I could opt for another solution: have the version in a version file, and read from both configure.ac and default.nix (see here for a solution) but I wold prefer that the nix related logic do not interfere with the original project.

I am open to any succestion.