bug#52107: An Idea

[Maxime Devos <maximedevos@telenet.be>]

Nicholas von Klitzing schreef op vr 26-11-2021 om 17:40 [+0000]:
> That's definitely a much better solution.
> 
> I'm having trouble finding documentation about both native-search-
> paths and wrap-program, so let me know if I understand your
> suggestions and how to apply them correctly.
> 
> The rust-1.18 package has a native-search-paths declaration:
> ``
> (native-search-paths
>      (list [...]
>            ;; Do you mean add something along the lines of
>            ;; this to every rust-xx package?
>            (search-path-specification
>             (variable "RUST_SRC_PATH")
>             (files '("library"))))) ;; I'm not sure what arguments

The package that is using RUST_SRC_PATH is rust-analyzer, not
rust@some-version. As such, the search path should be added to rust-
analyzer, not rust.

Search paths are added to the consumer, not the producer, as I've seen
it described somewhere.

Probably (separator #f) should be added, because I don't think rust-
analyzer supports using source code of multiple rusts at once.

> this takes
> 
> ``
> The directory structure of the rust repository, changes over time, so
> the paths would need to be adjusted depending on the version. Would I
> also need to add an additional build step to copy over the source and
> register it as an output?

The idea is to copy the unpacked source code to some output (let's call
it "source"). We would have to choose some subdirectory. Looking at the
package definition of rust-analyzer, it appears to like
‘lib/rustlib/src/rust’, so the source code could be copied to (string-
append #$output:src "/lib/rustlib/src/rust").

If that directory is used, files would be set to
'("lib/rustlib/src/rust").

> And for the rust-analyzer package we then add something along the
> lines of?
> 
> ``
> (add-after
>             'install 'wrap-rust-analyzer
>             (lambda* (#:key inputs outputs #:allow-other-keys)
>               (let ((out             (assoc-ref outputs "out"))
>                     (rust-src-path (getenv "RUST_SRC_PATH")))
>                 (wrap-program (string-append out "/bin/rust-
> analyzer")
>                   `("RUST_SRC_PATH" ":" prefix (,rust-src-path))))
>               #t))
> ``

Both wrapping and a search path wouldn't make much sense: the wrapping
would effectively override the search path, basically hard-coding the
source code used. Either go for a wrapper, a search path, or a wrapper
only setting the environment variable if it wasn't set already (*)(such
that the wrapper only sets a default).

(*) see docstring of wrap-program for how to do this, and whether it is
actually possible.

If you go for a wrapper instead of native-search-path, then
RUST_SRC_PATH would be unset in the build environment, so the (getenv
...) would need to be replaced with (search-input-directory (or native-
inputs inputs) "lib/rustlib/src/rust")).

Greetings,
Maxime