On Fri, Feb 18, 2022 at 10:28:29AM +0100, Wim de With wrote: Licensing is a pretty fun minefield :) For example, even though libvirt-rs itself would be statically linked into any application that uses it, by virtue of it being a wrapper around the C library you'd still end up dynamically linking against that. I tend to agree that language bindings should follow the rest of the language ecosystem in terms of licensing, and for libvirt-rs specifically that would probably mean MIT. Perhaps we should consider looking into relicensing the project?

On Fri, Feb 18, 2022 at 10:28:29AM +0100, Wim de With wrote: > Hello, > > I was reading the Rust bindings for libvirt and I noticed that they are > not very idiomatic. A couple of examples: > > 1. It is conventional to have a *-sys crate containing only the C > interface and the linking configuration. The virt crate would then > depend on this libvirt-sys crate to implement a safe and ergonomic > wrapper. > 2. The API heavily uses integers to indicate flags. Sometimes those > integers are type aliased and sometimes they are not. In Rust, this can > be much nicer, using enums to represent only valid flags. The same > applies to some return values. > 3. Since libvirt is thread-safe, the Rust types could be Send and Sync, > so that they can also be used in a multithreaded context. Special care > needs to be taken with translating virGetLastError to Rust Results, but > it shouldn't be a problem. > > For a nice example of a Rust wrapper around a C library, see: > https://github.com/rust-lang/git2-rs > > I am willing to send some patches to fix some of these problems, but > this will almost certainly lead to breaking API changes, and I am not > sure what your opinion is on that. We are aware of the issues with the current API of libvirt-rs, but unfortunately nobody has been able to dedicate time to addressing them. Any contributions towards that goal that you or anyone else could make would certainly be greatly appreciated! Breaking the API should be fine I think. The current version number is 0.2.11, so there shouldn't be any expectation in terms of API stability. Note that libvirt-python is mostly autogenerated, and there is an ongoing effort to make the same happen for libvirt-go-module. Ideally libvirt-rust would also follow this trend and end up with very little manually-written code in it.

> Finally, while I am not a legal expert, I believe that licensing a Rust > library as LGPL does not make much sense. Rust does not have a stable > ABI so everything is statically linked. This means that adding virt to a > Cargo.toml file of a non-GPL application is already in violation of the > license.

Licensing is a pretty fun minefield :) For example, even though libvirt-rs itself would be statically linked into any application that uses it, by virtue of it being a wrapper around the C library you'd still end up dynamically linking against that. I tend to agree that language bindings should follow the rest of the language ecosystem in terms of licensing, and for libvirt-rs specifically that would probably mean MIT. Perhaps we should consider looking into relicensing the project?

> Since the intent of libvirt using LGPL was explicitly to allow non-GPL > compatible applications to use libvirt, it is a mistake to be using > a license that breaks this ability for Rust. > > In Golang we've used MIT license > > For Rust we should aim for whatever is most appropriate - MIT or BSD > or Apache - I'm not familiar with which is dominant in the Rust world. Apache and MIT or even dual licensing of both are the most common. The official API guidelines recommend dual licensing under Apache and MIT.

On Mon, Feb 21, 2022 at 10:21:32AM -0500, Andrea Bolognani wrote: > We are aware of the issues with the current API of libvirt-rs, but > unfortunately nobody has been able to dedicate time to addressing > them. Any contributions towards that goal that you or anyone else > could make would certainly be greatly appreciated! > > Breaking the API should be fine I think. The current version number > is 0.2.11, so there shouldn't be any expectation in terms of API > stability. I realized that GitLab is nowadays used for communication so I made more specific issues there. Do you prefer merge requests there or patches on the mailing list?

> Note that libvirt-python is mostly autogenerated, and there is an > ongoing effort to make the same happen for libvirt-go-module. Ideally > libvirt-rust would also follow this trend and end up with very little > manually-written code in it. I've done some experiments here with bindgen, and it is pretty straightforward to generate FFI bindings using it. The problem is that generating safe idiomatic Rust wrappers on top of these bindings is non-trivial. Still, most wrapper functions will probably follow the same pattern, so it may be useful to investigate if macros could be used to make it easier to add new functions. >From looking at the Git diff from v2.5.0 to v8.0.0, the libvirt API doesn't seem to change that often. Almost all changes consist of adding new enum variants and some new functions. Am I correct in assuming that an application that was written for v2.5.0 would still work with v8.0.0?

To me it seems the best course of action would be to pick some minimum version of libvirt to support, and make sure that the Rust API wraps all functions there. From that point, adding functions and enum variants introduced in later versions of libvirt can be incremental changes and will (hopefully) be fairly easy to add. Rust has the concept of features to enable conditional compiling of those functions and enum variants only when the underlying libvirt supports them.