Eth JSON-RPC: eth_subscribe should take 0 or 1 argument

[ychiaoli18]

Based on the doc, eth_subscribe should take 0 or 1 argument.

• newHeads or pendingTransactions: take 0 argument
• logs: takes 1 argument

Code to reproduce

Reproduce with wscat

Connected (press CTRL+C to quit)
> {"jsonrpc":  "2.0",  "id":  1,  "method":  "eth_subscribe",  "params":  ["newHeads"]}
< {"jsonrpc":"2.0","id":1,"error":{"code":-32602,"message":"wrong param count (method 'eth_subscribe'): 1 != 2"}}

Connected (press CTRL+C to quit)
> {"jsonrpc":  "2.0",  "id":  1,  "method":  "eth_subscribe",  "params":  ["newHeads", null]}
< {"jsonrpc":"2.0","result":1,"id":1}

Reproduce with web3.js

const Web3 = require('web3');

const host = '<RPC_endpoint'>;

const web3 = new Web3('ws://' + host + '/rpc/v0')

const subscription = web3.eth.subscribe('newBlockHeaders', function(error, result){
  console.log(error, result);
});

setInterval(() => {}, 1 << 30);

Returned error:
Error: Returned error: wrong param count (method 'eth_subscribe'): 1 != 2