didc -t rs should implement serialize for records and variants

[lastmjs]

Is your feature request related to a problem? Please describe.

I am trying to use the generated Rust Candid types for use in Azle (TypeScript CDK), but I am running into this error when I try to have a record type as a parameter: the trait Serialize is not implemented for User`.

Describe the solution you'd like

For a simple Candid type like this:

type User = record {
  id: text;
};

The Rust code currently looks like this:

use ic_cdk::export::candid::{self, CandidType, Deserialize};
use ic_cdk::api::call::CallResult;

#[derive(CandidType, Deserialize)]
struct User { id: String }

It would be nice if Serialize could also be in the derive macro:

use ic_cdk::export::candid::{self, CandidType, Deserialize, Serialize};
use ic_cdk::api::call::CallResult;

#[derive(CandidType, Deserialize, Serialize)]
struct User { id: String }

Describe alternatives you've considered

This could also be set as a feature in Cargo.toml.

Additional context

It would be nice to have the option of configuring things like this on the types output by didc -t rust. I am happy to do a PR, though I believe this fix is probably pretty simple.

[chenyan-dfinity]

We plan to add a config struct to control the generated code, similar to the protobuf builder: https://docs.rs/prost-build/latest/prost_build/struct.Config.html#method.type_attribute

[lastmjs]

Would this help when I am using didc -t rs? I will be using the command line or the Rust API.

[chenyan-dfinity]

The CLI can take a config file as input, haven't thought about the format of the config file yet.

[lastmjs]

Could we also add an option to choose if nat outputs candid::Int or i128 and if int outputs candid::Nat or u128?

[chenyan-dfinity]

Yep, all Candid types should be able to map to a user specified type.

[chenyan-dfinity]

Duplicate of #255