How can I print solana error log messages in rust?

Question

I am able to see my custom error messages (defined on chain) when I call the [anchor] program using javascript client node client.js:

error: {
    errorCode: { code: 'MEOW', number: 6003 },
    errorMessage: 'This account a custom err message that I have written',
    comparedValues: undefined,
    origin: { file: 'programs/helloworld/src/lib.rs', line: 46 }
  },

the errorCode and errorMessage are especially helpful. How can I print those fields using Rust? Right now, I am only getting

Error: RPC response error -32002: Transaction simulation failed: Error processing Instruction 0: custom program error: 0x1774 [5 log messages]

Caused by:
    0: RPC response error -32002: Transaction simulation failed: Error processing Instruction 0: custom program error: 0x1774 [5 log messages]
    1: RPC response error -32002: Transaction simulation failed: Error processing Instruction 0: custom program error: 0x1774 [5 log messages]

my rust client code follows this template:

fn main() -> Result<()> {
    call_instruction()?,
    Ok(())
}

fn call_instruction() -> Result <()> {
    let program = ...;

    let signature = program
    .request()
    .accounts(program::accounts::Test {
        user: program.payer(),
    }).args(program::instruction::Testing {}).send()?;

    println!("Transaction signature: {:?}",signature);
    Ok(())
}

In terminal, I have tried setting env variable RUSTLOG=solana_client=debug before running cargo run, but nothing happens :(

Answer 1

If you wanted to print in the context of a test, you might do something like:

#[test]
fn some_test() {
 let result = call_instruction();
 if result.is_err(){
  //whatever
 }
}

And here you could extract the error (result.err()) if you wanted to print the log or code.

More commonly you have some errorCode values specified in your errors.rs, you are emitting these with return err!(ErrorCode::Whatever); when something goes wrong, and this gets caught and printed by the caller.

Answer 2

RpcClient is returning an error type of "solana_rpc_client_api::client_error::Error". This Error type contains a member field called "kind" that can be matched against. For example, to map this to anyhow::Error:

    use solana_rpc_client_api::client_error::ErrorKind;
    // ...
    rpc_client
      .send_and_confirm_transaction_with_spinner(&transaction)
      .await.map_err(|e| {
        match e.kind {
        ErrorKind::RpcError(rpc_err) => {
          println!("ERROR: {rpc_err:?}");
          Error::new(rpc_err)
        }
          // match other types
          _ => { Error::new(e) }
        }
    })

More specifically, the log messages you are looking for are likely buried down under: ErrorKind/RpcError/RpcResponseError/RpcResponseErrorData/SendTransactionPreflightFailure/RpcSimulateTransactionResult/logs.