As of Rust v1.62, enums can now use #[derive(Default)]

[mimullin-bbry]

Rust version 1.62 stabilized using derive(Default) for enums by marking the #[default] value to be used

See: rust-lang/rust#94457

Rust version 1.69 (unsure about 1.68) will start throwing a clippy warning for using manual impl Default when the derive(Default) can be used. These warnings will apply to the generated skeletons created by libbpf-cargo, causing issues to users.

    = help: for further information visit https://rust-lang.github.io/rust-clippy/master/index.html#derivable_impls
    = note: `#[warn(clippy::derivable_impls)]` on by default
    = help: remove the manual implementation...
help: ...and instead derive it...

libbpf-cargo should either update the minimum version to 1.62 and use the derive(Default) in this area of the code (https://github.com/libbpf/libbpf-rs/blob/master/libbpf-cargo/src/btf/btf.rs#L989). Or a #![allow(clippy::derivable_impls)] can be added to this area of the code (https://github.com/libbpf/libbpf-rs/blob/master/libbpf-cargo/src/gen.rs#L684), and the MRV can stay at 1.58.0

[danielocfb]

Thanks for pointing that out. It does not seem worth it to bump our minimum supported Rust version by four for this minor improvement, to be honest, so I am tempted to just suppress the warning, and include a TODO to fix this up once we require this version anyway. Are you interested in creating a pull request by any chance, @mimullin-bbry ?

[mimullin-bbry]

Are you interested in creating a pull request by any chance, @mimullin-bbry ?

I am, I just was interested in guidance about which path the project would prefer. The "stay with 1.58" is a much less invasive and easier to implement fix (just plop in the allow and be done with it), however the derive(Default) method makes the generated skeletons slightly more readable (though not by much tbh). Also, the clippy warning isn't specific to just enums; suppressing the warning means the project will miss out on methods to make the generated skeletons "cleaner" in the future.

[danielocfb]

Sounds good. Yeah, I am not saying we should never go with #[default] on variants, just to postpone doing so until we bump to 1.62 for other reasons. But admittedly, we have no hard requirements for staying on 1.58, so if you feel strongly about going all the way, be my guest.

suppressing the warning means the project will miss out on methods to make the generated skeletons "cleaner" in the future

Fair enough. I am not too worried about that, though. For one, we should try and tag the smallest entity in question (the very enum definition or Default impl); in which case I'd expect we still see a warning for other types in the future. But it's also unlikely that we won't notice it through other avenues (e.g., by following Rust changelog announcements).

[mimullin-bbry]

I'll go with the "stick to 1.58".

FYI: Beta just updated to 1.68, and the clippy warning is occurring. Thus, this issue might start impacting people's work flows. I'll try and get an MR ready this evening after work.

[mimullin-bbry]

#334