How can dependencies of recipes be specified?

[aspiwack]

(I'm asking so, of course it's going to be in the documentation somewhere and I just failed to find it. So: apologies in advance)

I couldn't find in the documentation how to specify dependencies for Nix to use when building non-Melpa recipes.

Specifically, I have the following in my packages.el:

(package! elastic-indent
  :recipe (:type git :host github :repo "jyp/elastic-modes")
  :pin "c577e8921a4d9bd77742729707152bc557fae3e2"
  )

And The build fails with

Cannot open load file: No such file or directory, dash

I assume that this means that the dependency on Dash isn't declared in the Nix derivation corresponding to elastic-indent. But I don't know how to tell Nix-doom-emacs-unstraightened to pick up on this dependency.

[marienz]

If there is a derivation in emacs-overlay (or nixpkgs), it uses those dependencies (which won't always work if you pin to a sufficiently different version). If not, it autodetects them from headers in the package.

(...and no, I don't think that's documented.)

For this package, we hit the latter, but it does not work because although it specifies its dependency in a -pkg.el file, we do not parse those (see also melpa/melpa#9285) and it's not called elastic-indent-pkg.el so (from memory) we wouldn't have parsed it before either. If there was a ;; Package-Requires: ((emacs "29.1") (dash "2.19.1")) header in elastic-indent.el it should've worked (or in elastic.el and you'd have to use (package! elastic ...))

I don't think there's currently a good answer here. If you don't need the same package.el to work elsewhere, I think if you remove elastic-indent there and pass

              extraPackages = (
                epkgs: [
                  (epkgs.melpaBuild {
                    pname = "elastic-indent";
                    version = "9999snapshot1";
                    packageRequires = [ epkgs.dash ];
                    src = builtins.fetchTree {
                      type = "github";
                      owner = "jyp";
                      repo = "elastic-modes";
                      rev = "c577e8921a4d9bd77742729707152bc557fae3e2";
                    };
                  })
                ]
              );

to our home-manager module that'll work, but it's... clunky.

It's really the same problem as #51, just with a different setting... I should sit down and figure that "overlay-ish" feature mentioned there out at some point.

[aspiwack]

It did work, indeed. Thank you!

In order to cleanly close this, I'm proposing some documentation at #71.