Hi Ludo,
Am 30.04.21 um 12:45 schrieb Ludovic Courtès:
Uh. More generally, Rust packages kinda create a “shadow dependency
graph” via #:cargo-inputs & co., which breaks all the tools that are
unaware of it. It was discussed several times on this list, and
apparently it’s unfortunately unavoidable at this time. :-/
Maybe we can get rid of #:cargo-inputs at least:
guix/build-system/cargo.scm says: "Although cargo does not permit cyclic
dependencies between crates,
however, it permits cycles to occur via dev-dependencies"
So we could change #:cargo-inputs into normal inputs and get at least
part of the dependencies right.
I'm aware of the "special treatment" of cargo-inputs. Anyhow we could
apply the following changes to the cargo build-system:
*
The cargo build-system copies the "pre-built crate" (more on this
below) into a new output called "rlib" or "crate". There already is
a phase "packaging" which only needs to be changed to use the other
output.
*
All of today's #:cargo-inputs will be changed into normal inputs
using the "rlib/crate" output. (To avoid duplicate assoc-rec keys we
might need to change the name/keys, but this should be a minor issue.)
*
If required, the cargo build-system can easily identify former
#:cargo-inputs by being inputs from a "rlib/crate" output.
Benefits up to here:
* The dependency graph would be much more complete - although
"#:cargo-development-inputs" would still be missing.
* Package transformation options would work -again except for
"#:cargo-development-inputs".
* If(!) we actually manage to make cargo pick "pre-built" crates,
package definition will already be adjusted to use them.
|Drawbacks up to here:|
* ||Since the "packaging" phase copies the source, there is not much
benefit in having a "rlib/crate" output yet. Actually, when a
"rlib/crate" output needs to be build, the user will end up with two
copies of the source (one from the git-checkout, one from packaging)
About "pre-built" crate: Given the many possible ways to build crates
(e.g. switching on and off "features", different crate types), we might
never be able to provide pre-built packages for all cases. Thus we might
end up always providing the source, even if we manage to make cargo pick
of pre-built artifacts.
About the output name: Rust has a notion of "rlib" (a specialized .a
file), which seems to be the pre-built artifacts we are seeking. Thus
the proposed name.
WDYT?
--
Regards
Hartmut Goebel
| Hartmut Goebel | [email protected] |
| www.crazy-compilers.com | compilers which you thought are impossible |
