How to use NCI-based flake output as input of another?

[nothingnesses]

Hi. I'm trying to use the output of an NCI-based flake as the input of another, but I can't get it to work.

Here is a repository of a minimal reproduction where I made a flake for cargo-generate which I'm trying to use inside the dev shell of another flake.

Running nix shell .#cargo-generate from "./cargo-generate" successfully drops me to a shell where I can use cargo generate.

However, running nix develop from "./" results in the following error:

$ nix develop
error: attribute 'defaultPackage' missing

       at /nix/store/bkgy2dvg91a8578w59534z75nsfy2jbd-source/flake.nix:190:17:

          189|               path = lib.makeBinPath [
          190|                 alejandra.defaultPackage.${system}
             |                 ^
          191|                 pkgs.python3.pkgs.black
(use '--show-trace' to show detailed location information)
$

How can I figure out why this is happening and what can I do to get this to work?

[yusdacra]

It doesn't look like that issue relates to nix-cargo-integration but rather to dream2nix, as in the code comes from there, but I'm not sure why that would be an error (unless you changed dream2nix's alejandra input?). The repo you linked doesn't seem to be available so I couldn't take a look at it. If you can link a new one here I can take a look at it.

[nothingnesses]

Thanks, but unfortunately that doesn't seem to work:

$ nix develop
warning: Git tree '/home/a/tmp/nci' is dirty
error: attribute 'default' missing

       at /nix/store/wlb0fmznr0h3c4r0mj8sjw6vw7z70azn-source/flake.nix:29:56:

           28|         shell = {
           29|           packages = builtins.map (element: {package = inputs.${element}.packages.default;}) ["cargo-generate"];
             |                                                        ^
           30|         };
(use '--show-trace' to show detailed location information)
$

[yusdacra]

You can either set the outputs.defaults config option in the cargo-generate flake or just replace that line with:

packages = [inputs.cargo-generate.packages.cargo-generate];

[nothingnesses]

Thanks, but I've already set that config option in the cargo-generate flake.

I tried your other suggestion, but it results in the following error:

$ nix develop
warning: Git tree '/home/a/tmp/nci' is dirty
error: attribute 'cargo-generate' missing

       at /nix/store/913a2f27vyh4viyhc6lrgyjwk8kaqh6z-source/flake.nix:29:56:

           28|         shell = {
           29|           packages = builtins.map (element: {package = inputs.${element}.packages.${element};}) ["cargo-generate"];
             |                                                        ^
           30|         };
(use '--show-trace' to show detailed location information)
$ git add .
$ nix develop
warning: Git tree '/home/a/tmp/nci' is dirty
error: attribute 'cargo-generate' missing

       at /nix/store/mg5h7va0ffln9pw6z8iqrw7mxh6sj1yk-source/flake.nix:29:23:

           28|         shell = {
           29|           packages = [inputs.cargo-generate.packages.cargo-generate];
             |                       ^
           30|         };
(use '--show-trace' to show detailed location information)
$

[yusdacra]

Oh sorry, I mixed it up. You need to use inputs.cargo-generate.packages.${common.pkgs.system}.cargo-generate. Since this is from the flake inputs, it will be structured like packages.<system>.<package name>. I'm actually currently rewriting NCI itself (see #110) to reduce this kind of friction and make it more modular and integrate-able with other stuff. It's pretty close to being merged, so I would be very happy if you could try that, the branch should have a few examples. (though no rendered documentation yet, so you would have to rely on reading the modules code itself, or just DM me on matrix).

[nothingnesses]

Thanks. I'll try using that branch. I've been going through the flake.parts documentation, but it's quite long, so I probably won't be able to learn enough of it to successfully adapt my example project from above until tomorrow. I'll keep you apprised of my progress.

[nothingnesses]

Thanks. I've had to change inputs.cargo-generate.packages.${common.pkgs.system}.cargo-generate to inputs.cargo-generate.packages.${pkgs.system}.default, as well as fork NCI to add a feature that let me set --no-default-features (I've submitted a PR for it) since I kept running into PermissionDenied errors during the build stage of libgit2-sys without that, but other than those, your solution seems to work.

[nothingnesses]

For posterity, the fork is no longer required as this commit adds a feature that allows --no-default-features to be set. Here's an example usage.