Hi! We stumbled upon an idiom for package arguments that, combined with package inheritance, would not work as expected. It goes like this (taken from <https://gitlab.inria.fr/guix-hpc/guix-hpc/>):
--8<---------------cut here---------------start------------->8--- (define-public starpu (package ;; … (arguments (substitute-keyword-arguments (package-arguments starpu-1.2) ((#:configure-flags flags '()) (match (assoc "mpi" (package-propagated-inputs this-package)) (("mpi" mpi) (if (string=? (package-name mpi) "nmad") `(cons "--enable-nmad" ,flags) flags)))))) (propagated-inputs `(("mpi" ,openmpi))))) (define-public starpu+fxt (package (inherit starpu) ;; … (arguments (substitute-keyword-arguments (package-arguments starpu) ((#:configure-flags flags '()) `(cons "--with-fxt" ,flags)))))) --8<---------------cut here---------------end--------------->8--- The first package, ‘starpu’, has its arguments depend on: (package-propagated-inputs this-package) This is smart because if you inherit from it without changing the ‘arguments’ field (for instance by doing ‘--with-input=openmpi=nmad’), it’ll adjust its configure flags based on the MPI package it actually depends on. However, this trick doesn’t work with the second package, ‘starpu-fxt’: if you do: guix build starpu-fxt --with-input=openmpi=nmad the ‘--enable-nmad’ configure flag will not be passed. This is because ‘starpu-fxt’ calls: (package-arguments starpu) which returns the original arguments of ‘starpu’. Still here? :-) This is admittedly a pretty far-fetched example and there are ways to work around it¹. Still, I wonder if we could up with a linguistic device (ah ha!) to address that. We don’t want to (package-arguments this-package) here: that would naturally lead to an infinite loop. But we want something close to it, in spirit: (package-arguments parent), where ‘parent’ is the package we inherit from. (package-arguments parent) could call the ‘arguments’ thunk of the parent, but it would pass it the child as its argument. Or something like that. Thoughts? Ludo’. ¹ https://gitlab.inria.fr/guix-hpc/guix-hpc/-/commit/761cfe97d5bb42dbbde538593cef93e803086e3b