[PATCH RFC] Turning Rust/Cargo inputs into “regula r” inputs?
(address . bug-guix@gnu.org)
87sfty3yb5.fsf@inria.fr
Hello!
I’m opening this issue to discuss the possibility of changing
#:cargo-inputs and #:cargo-development-inputs to regular inputs, as a
followup to:
I have a preliminary patch for ‘guix style’ and (guix build-system
cargo), but there’s a couple of stumbling blocks.
First, after the hacky patch in the discussion above, I attempted to
turn #:cargo-inputs into ‘propagated-inputs’ (instead of ‘inputs’),
because that seemed to be somewhat more logical. That cannot work
though, because then those packages would propagate to non-Rust
packages; for example, librsvg would depend on the “build output” of
rust-* instead of just depending on its source. Anyway, I’m back to
‘inputs’.
Second, until now, these two things would have a different meaning:
#:cargo-inputs (list rust-cargo)
vs.
(inputs (list rust-cargo))
In the latter case, the package depends on the build result of
‘rust-cargo’; in the former case, the package depends on the source of
‘rust-cargo’. (See ‘rav1e’ for an example where this happens.)
If we turn all #:cargo-inputs into ‘inputs’, how can we distinguish
these two cases? A package like ‘rust-cargo’ is sometimes depended on
for its source, sometimes for its build result; thus, we cannot just
annotate the ‘rust-cargo’ package itself.
Last, the change to ‘inputs’ would introduce a few cycles at the
<package> level. Those cycles vanish when we lower to bags and
derivations. However, because of these cycles, things like ‘guix
refresh -l’ may not work; there might be other unexpected and undesired
side effects.
Some of these cycles could in theory be removed. For instance,
‘rust-cfg-if’ has an optional dependency on ‘rust-compiler-builtins’,
which leads to a cycle, but Cargo won’t let us actually remove that
dependency, even though it’s optional.
In short: it’s complicated!
Thoughts? Is status quo a lesser evil, after all?…
Ludo’.
PS: I guess you already knew all this Efraim but I’m kinda
(re)discovering it and now experiencing frustration firsthand. :-)