Get serde parse error when call block_results

[hashableric]

What went wrong?

I just write simple code for get latest block result from osmosis json-rpc.
Because the version of osmosis tendermint is v0.34, I tried compat mode V0_34 too. It isnt changed.
When I call the client.perform method, the response always serde parse error

Steps to reproduce

Here's core I wrote

use tendermint_rpc::{endpoint::block_results, Client, HttpClient};

#[tokio::main]
async fn main() {
    let client = HttpClient::new("https://rpc.osmosis.zone:443").unwrap();
    let result = client.perform(block_results::Request::default()).await;

    println!("{:?}", result);
}

I also attach v0.34 code

use tendermint_rpc::{endpoint::block_results, Client, HttpClient, HttpClientUrl};

#[tokio::main]
async fn main() {
    let url = HttpClientUrl::try_from("https://rpc.osmosis.zone:443").unwrap();
    let client = HttpClient::builder(url)
        .compat_mode(tendermint_rpc::client::CompatMode::V0_34)
        .build()
        .unwrap();

    let result = client.perform(block_results::Request::default()).await;

    println!("{:?}", result);
}

Here's the Cargo.toml

[package]
name = "cosmrs-test"
version = "0.1.0"
edition = "2021"

# See more keys and their definitions at https://doc.rust-lang.org/cargo/reference/manifest.html

[dependencies]
cosmrs = { version = "0.14.0", features = ["cosmwasm", "rpc", "tokio", "grpc"] }
tokio = { version = "1.29.1", features = ["full"] }
tendermint-rpc = { version = "0.32.0", features = ["http", "tokio"] }

When try to execute program, I got

Err(serde parse error

Caused by:
    invalid type: null, expected a string at line 1 column 196492

Location:
    /Users/eric/.cargo/registry/src/github.com-1ecc6299db9ec823/flex-error-0.4.4/src/tracer_impl/eyre.rs:10:9)

Definition of "done"

Able to get block_results from osmosis json-rpc.

[hashableric]

EventAttribute's value attribute is currently not nullable. The response of the block_results actually has null suck as memo key. It's cause this error IMO

[mzabaluev]

tendermint-rpc = { version = "0.32.0", features = ["http", "tokio"] }

The feature list must have been ["http-client"], otherwise the code does not compile.

I can confirm the error even with the 0.34 compatibility mode. Will investigate.

Unfortunately, this is not expected to work correctly with a 0.34 node, as the protocol has changed and we lack the means to auto-detect it reliably, other than hitting the status endpoint:

use tendermint_rpc::{endpoint::block_results, Client, HttpClient};

#[tokio::main]
async fn main() {
    let client = HttpClient::new("https://rpc.osmosis.zone:443").unwrap();
    let result = client.perform(block_results::Request::default()).await;

    println!("{:?}", result);
}

[mzabaluev]

The cause, in this example, is that the example uses the perform method directly which bypasses the backward compatibility logic. If you use the block_results method, the implementation switches to the perform_v0_34 intrinsic method and the response is parsed successfully.
I noticed, however, that the latest_block_results method does not properly implement this, so there is a bug that needs to be fixed.

It's confusing now that the perform method is exposed in the public API; when initially defined, it wasn't a problem, but with the compatibility mode support added on, this becomes an implementation detail.

[mzabaluev]

This method doc on Client::perform perhaps does not carry enough warning against using the method in consumer code:

    /// This method is used by the default implementations of specific
    /// endpoint methods. The latest protocol dialect is assumed to be invoked.