Vec<u8> does not map to Uint8Array when using serde_bytes

[hexadecimal233]

When using specta to generate TypeScript types for a Rust struct containing a Vec<u8> annotated with serde_with = "serde_bytes", the generated frontend types do not align with the Uint8Array expected by MessagePack. (the protocol im using in creating frontend app)

Currently Specta ignores the serde_bytes logic and attempts to treat Vec<u8> as a standard number[].

There's a workaround to trick the compiler:

#[derive(Type, Serialize, Deserialize)]
pub struct MyPayload {
    #[specta(type = Unknown)] // Workaround to bypass TS errors
    #[serde(with = "serde_bytes")] 
    pub screenshot: Vec<u8>,
}

[oscartbeaumont]

This is related to #203 so it is planned but the exact implementation is still a wip. I started a prototype #419 here but haven't had a chance to properly hook it up in a downstream framework like Tauri Specta.

As much as Specta's core is going to implement the primitives to support this feature I suspect it won't fully work without a framework ontop like Tauri Specta, rspc or TauRPC because for types like Date's we are going to need runtime code to map the runtime type properly.

The fact that MessagePack decodes this way is pretty interesting though because I think when we support this feature we are probally going to need a way for exporters (Eg. Typescript) to define how they map internal types. Eg. MessagePack maps Vec<u8> -> UInt8Array while JSON maps it to number[]. This would be a generalisation of the current BigIntExportBehavior.

Will report back as I make more progress on this!

[temeddix]

This is indeed a needed change. Currently there is no way to pass binary data between TypeScript and Rust (Except for ineffecient base64 encoding)