serde serialization and deserialization support

[ngerow2025]

There is no way to currently encode chess positions from this crate in an efficient way with a binary encoding and serde support would enable this without much trouble. I am willing to implement this through a feature flag with all of the public facing types in the crate.

[niklasf]

Hi. The reason why I've been hesitant to add this, is that there's no single best way to implement these traits. For example, for efficient IPC, I'd expect Square::A1 to be serialized as 0. For a public facing JSON API, I'd find "a1" more suitable.

Types do implement common traits like TryFrom, Into, FromStr, and Display. I find serde_with useful to explicitly explicitly choose the format.
For example, serde_with::TryFromInto for round trips via integers, serde_with::DisplayFromStr for round trips via string representations.

[icp1994]

Any tricks with which I can de/ser ArrayVec<T, CAP>? I have something like this:

#[derive(Serialize, Deserialize)]
pub struct OrderedSan {
    pub sans: ArrayVec<SanPlus, 128>,
}

arrayvec has serde support but I can't seem to make it integrate with DisplayFromStr.

edit: the following works but not the most ergonomic

#[serde_as]
#[derive(Serialize, Deserialize)]
pub struct SanPlusWrapper {
    #[serde_as(as = "DisplayFromStr")]
    pub sp: SanPlus,
}

#[derive(Serialize, Deserialize)]
pub struct OrderedSan {
    pub sans: ArrayVec<SanPlusWrapper, 128>,
}

[niklasf]

More workarounds ... if allocating a Vec is acceptable:

#[serde_as]
#[derive(Serialize)]
struct Example {
    #[serde_as(as = "Vec<DisplayFromStr>")]
    moves: Vec<SanPlus>,
}

Or borrowing to serialize:

#[serde_as]
#[derive(Serialize)]
struct Example<'a> {
    #[serde_as(as = "&[DisplayFromStr]")]
    moves: &'a [SanPlus],
}

[icp1994]

I currently have the Vec implementation, was trying to move to arrayvec to see if I could get some perf gains :)

[kraktus]

It's because arrayvec does not implement SerialiseAs and DeserialiseAs. I implemented them: bluss/arrayvec@master...kraktus:arrayvec:serde_with
and will try to merge it upstream under the serde or new serde_with feature, but I expect the patch to be rejected. I'll then try to add it as a arrayvec07 feature to serde_with where I've more hope it'll be accepted.

Side note. The SerialiseAs/DeserialiseAs is a type hell and I didn't really understand how it worked but tests pass so should be good.

Working version with the patch. For a binary, using a git dep is fine.

// in Cargo.toml
// arrayvec = { git = "https://github.com/kraktus/arrayvec", branch = "serde_with", features = ["serde"] }
#[serde_as]
#[derive(Serialize, Deserialize)]
pub struct Native {
    #[serde_as(as = "ArrayVec<DisplayFromStr,128>")]
    pub sans: ArrayVec<SanPlus, 128>,
}