Eth::block() not working for BlockNumber::Pending

[fleupold]

The following example code:

use web3::futures::Future;
use web3::types::BlockNumber;
fn main() {
    let (_eloop, transport) =
        web3::transports::Http::new("https://node.mainnet.gnosisdev.com").unwrap();

    let web3 = web3::Web3::new(transport);
    let block = web3
        .eth()
        .block(BlockNumber::Pending.into())
        .wait()
        .unwrap();

    println!("Block: {:?}", block);
}

Fails with the following error:

thread 'main' panicked at 'called Result::unwrap() on an Err value: Decoder("Error("invalid type: null, expected a 0x-prefixed hex string with length of 512", line: 0, column: 0)")', src/main.rs:8:17

The problem seems to be that the RPC response for a pending block (parity client) contains null for logs_bloom (512 hex characters = 2048 bit) and this field is not optional on the Block struct.

Is there a reason for this? Do consumers expect logs_bloom to be always set? Would it be a valid change to make this field optional or could we alternatively tighten the interface to not allow querying block() for Pending?

[tomusdrw]

The Block struct in rust-web3 was based on the one returned by Parity Ethereum, but it was a long while ago. Seems that this change: https://github.com/openethereum/openethereum/pull/8281 was not reflected in web3 copy of the Block struct.

I think we should just change the logs_bloom to be an Option, PR welcome :)