Provide a default for Rid

[fpdotmonkey]

A default value for Rid makes it possible to use it as a member of GodotClass-derived struct, which can be useful for custom Resources.

The default value of Invalid is both logical--it shouldn't point to any resource a user doesn't specify--and it's what's done in-engine (godot@46dc27/core/templates/rid.h:40 - uint64_t _id = 0;).

[GodotRust]

API docs are being generated and will be shortly available at: https://godot-rust.github.io/docs/gdext/pr-623

[Bromeon]

You should have waited for the response on Discord 😉

I'm not a huge fan of adding Default for types whose default representation is invalid; rationale see here.

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A default value for Rid makes it possible to use it as a member of GodotClass-derived struct, which can be useful for custom Resources.

You can achieve this with #[init(default = Rid::Invalid)] or an overridden init() method -- both are more explicit.

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Btw, the API of Rid might become more like InstanceId in the future.
Its current definition

pub enum Rid {
    Valid(NonZero<u64>),
    Invalid,
}

is not great, because Rid::Valid is not its own type, so you can't express that you have a valid Rid and need to defensively check is_valid()/is_invalid() in the code...

If we had something like type Rid = Option<ValidRid>, then you could simply reuse all the outer APIs, including Option::default(). This might need a bit more discussion, since Callable and Signal are very similar, and maybe even some geometric types like Plane.

[fpdotmonkey]

This seems reasonable. I'll close this.