Plan for `spglib` transition

[LecrisUT]

There are a few topics to discuss

How to provide C and C++ interface

If we can provide a spglib.h compatibility interface, then developing the Fortran equivalent would also be possible. Right now I know the link from CMake to rust is well developed, but I don't know about example of the inverse.

For compatibility purposes we also need a to provide some SpglibConfig.cmake files. This part should be relatively easy to develop using appropriate find_library and such.

Integrating CI coverage

At the minimum we would need coverage for cibuildwheel and various matrix test cases since now the rust version on the system is also a variable.

Packaging concerns

Rust has a more specific packaging guidelines, so it will be a bit more involved to maintain a rust-moyo and moyo package. One thing to note, is that even though rust tends to have static Cargo.lock dependencies, Fedora packaging does not vendor those dependencies and as such, in order to make distro packaging easier, we should track what is available there as well.

One particular issue is that if you use Cargo.lock to define the dependencies you use, you are implicitly responsible for tracking the dependent projects CVE (security issues).

[lan496]

I have not tried it yet, but https://github.com/rust-lang/rust-bindgen would be used to generate C and C++ interfaces.
Personally, I want to make the Rust-side build system (currently only using cargo) as small as possible.

[LecrisUT]

Unfortunately, bindgen does the opposite, i.e. it makes it possible for rust to link to a C/C++ library, instead of creating a header file and dynamic library.

[LecrisUT]

I have found cbindgen and cxx, which seem to do the linking in the direction that we want.

[LecrisUT]

I got some more experience packaging rust for Fedora and I have a concrete recommendation. Please use the corrosion to offer a CMake package from it. In principle it is a drop-in addition to moyoc, the only difference is that you now run cmake commands to build.