Test Nix functionality

[alerque]

As a follow up to #1231, setup a CI workflow to test that the Nix Flake and other features stay in working order.

[alerque]

@doronbehar This error has be baffled. The default.nx in nixpkgs is only marked as broken for Darwin. I get the same error locally by the way. Any ideas?

error: Package ‘sile-0.11.1-dirty-flake’ in /nix/store/2c1s0cbii0v7gqxyklknp32ya3xa3nr6-source/pkgs/tools/typesetting/sile/default.nix:100 is marked as broken, refusing to evaluate.

[doronbehar]

@doronbehar This error has be baffled. The default.nx in nixpkgs is only marked as broken for Darwin. I get the same error locally by the way. Any ideas?

error: Package ‘sile-0.11.1-dirty-flake’ in /nix/store/2c1s0cbii0v7gqxyklknp32ya3xa3nr6-source/pkgs/tools/typesetting/sile/default.nix:100 is marked as broken, refusing to evaluate.

No idea at all.. Perhaps it would help to print the Nixpkgs revision used, as explained in here:

https://github.com/cachix/install-nix-action/#how-do-i-print-nixpkgs-version-i-have-configured

And perhaps we can print similar stuff to debug why it evaluates as broken:

- name: Print whether nixpkgs' stdenv is darwin
  run: nix-instantiate --eval -E '(import <nixpkgs> {}).stdenv.isDarwin'

This might work and help:

- name: Evaluate nixpkgs' sile.meta
  run: nix eval --json nixpkgs#sile.meta

I also noticed you didn't specify a nix channel with nix_path, do you think it doesn't matter because you use the Nixpkgs flake?

[doronbehar]

I'd try also:

- name: Evaluate nixpkgs' sile.meta
  run: nix eval --json .#sile.meta

when Inside the repository.

[alerque]

Thanks for the ideas. You can see the output of the debug info requested in this test run.

I also noticed you didn't specify a nix channel

I tried it with and without, it just happened to end on "without". It's back, but that isn't the (only?) problem.

Everything else looks as expected, including isDarwin being falsey.

[doronbehar]

I found it, we just had to RTFM:

This command verifies that the flake specified by flake reference flake-url can be evaluated successfully (as detailed below), and that the derivations specified by the flake's checks output can be built successfully.

If the keep-going option is set to true, Nix will keep evaluating as much as it can and report the errors as it encounters them. Otherwise it will stop at the first error.

It failed because it evaluated the derivation for all systems. You have a few options:

1. Remove the nix flake check
2. Not use flake-utils.lib.eachDefaultSystem and use: flake-utils.lib.eachSystem [ "supported systems here as a list" ]
3. Use nix flake check --keep-going but it will still exit with a non-zero code.

[alerque]

Thanks for the research! Is there a definitive list of supported systems we can use and just subtract Darwin?

[alerque]

I found the exact opposite of what I was looking for:

flake-utils.lib.eachSystem (
	flake-utils.lib.defaultSystems ++ ["x86_64-darwin"]
) (system:
	...

What I need is a list subtraction instead of a list concatenation operator.

[alerque]

lib.lists.subtractLists might do the job, or there may be a way to iterate defaultSystems and use stdenv.isDarwin to filter out the ones we don't want (similar to this but for systems not features), but I can't figure out an exact usage that works.

[doronbehar]

lib.lists.subtractLists might do the job, or there may be a way to iterate defaultSystems and use stdenv.isDarwin to filter out the ones we don't want (similar to this but for systems not features), but I can't figure out an exact usage that works.

I guess we can do that, but in general, what value do you see in nix flake check? It only checks that the derivations evaluate.. If I were you, I'd run only nix build -L .#sile and perhaps test that the compiled binary can compile a sample document? Perhaps even that is not needed, since the derivation runs the tests of the build system during build.

[alerque]

I believe this attempted work was obsoleted by 0ae6771 and we've been test building the flake in CI since before tagging v0.13.0.