RPC encoding regression in 2.6.1

[hkalodner]

Version 2.6.1 upgraded the dependency on web3-provider-engine from version 14.1.0 to version 14.2.0. This version upgrade contains a regression (also reported in MetaMask/web3-provider-engine#317).

The regression is a deviation from the rpc hex encoding specification described in https://github.com/ethereum/wiki/wiki/JSON-RPC#hex-value-encoding. 0 values are now encoded as "0x" when they should be "0x0". This causes errors in rpc client libraries that expect strict correctness like go-ethereum.

Expected Behavior

Calls to rpc methods which contain results including 0 values should correctly encode them as "0x0"

Current Behavior

Calls to rpc methods which contain results including 0 values encode them as "0x"

Possible Solution

This could be solved by either downgrading the web3-provider-engine dependency back to 14.1.0 or getting an upstream fix into web3-provider-engine and upgrading. If there are no other reasons why 14.2.0 is required, downgrading seems like the easiest immediate fix.

Steps to Reproduce (for bugs)

The following code will print the difficulty returned by ganache-core as 0x when running with 2.6.1 and 0x0 when running 2.6.0.

const ganache = require("ganache-core");
const WebSocket = require('ws');

ganache.server({blockTime: 1}).listen(7545);
var client = new WebSocket("ws://localhost:7545/");
client.onopen = function(e){
   this.send('{"id":1337,"jsonrpc":"2.0","method":"eth_subscribe","params":["newHeads", {}]}');
}
client.onmessage = function(response,flags,number)  {
   try {
       console.log(JSON.parse(response.data).params.result.difficulty);
   } catch(e) {}
}

Context

This came up trying to use ganache along with go-ethereum which forces strict adherence to the hex encoding in
https://github.com/ethereum/go-ethereum/blob/dbb03fe9893dd19f6b1de1ee3b768317f22fd135/common/hexutil/json.go#L358.

Specifically calls to SubscribeNewHead result in a JSON unmarshalling error due to this problem.

Your Environment

• Version used: 2.6.1
• Environment name and version (e.g. PHP 5.4 on nginx 1.9.1): Node v11.15.0
• Server type and version:
• Operating System and version: Mac 10.14.6
• Link to your project: https://github.com/OffchainLabs/arbitrum/blob/2e7e2299ef6f19167a8d8fbf042abe124fe13492/packages/arb-validator/ethbridge/ethbridge.go#L96

[kumavis]

patched in web3-provider-engine@14.2.1

[hkalodner]

Thanks @kumavis! It'd be great to get this dependency upgraded in this package. No wiggle room on the version pinning so it'll require an upgrade.