Can't invoke SRC7 metadata method from the rust SDK due to arbitrary nesting of heap types

[cold-briu]

Description

Can't invoke SRC7 metadata method from the rust SDK due to arbitrary nesting of heap types
Since metadata Returns an Option wrapping an Enum that evaluate to string.

let meta = contract_instance
        .methods()
        .metadata(asset_id, "key".to_string())
        .simulate()
        .await
        .unwrap();

Throws the following error:

thread 'main' panicked at 'called `Result::unwrap()` on an `Err` value: InvalidType("Enums currently support only one level deep heap types.")

contract_instance comes from the following implementation:

contract;

use src_7::{Metadata, SRC7};
use std::{call_frames::contract_id, hash::Hash, storage::storage_string::*, string::String};

impl SRC7 for Contract {
    #[storage(read)]
    fn metadata(asset: AssetId, key: String) -> Option<Metadata> {
        if key == String::from_ascii_str("key") {
            Some(Metadata::String(String::from_ascii_str("value")))
        } else {
            None
        }
    }
}

Then, the execution should return something like:

let result: Option<Enum<String>> = SRC7.metadata(myAsset, myKey);

Considering:

/// Universal return type for metadata.
pub enum Metadata {
    // Used when the stored metadata is a `b256`.
    B256: b256,
    /// Used when the stored metadata is `Bytes`.
    Bytes: Bytes,
    /// Used when the stored metadata is a `u64`.
    Int: u64,
    /// Used when the stored metadata is a `String`.
    String: String,
}

First incidence reported here.

[cold-briu]

Please check this blocker issue for further details.

[hal3e]

With the new encoding (v1) this is not an issue anymore.