Changes miningReward method to calculate the reward for block zero correctly

[thepabloaguilar]

Fixes #73

Motivation

This PR solves the bug for reward amount for block zero!

Solution

I've removed the if statement where it checks if a given block is the zero block or not, without that if the value was returned correctly.

Request:

curl -XPOST localhost:8080/block -d '{
  "network_identifier": {
    "blockchain": "Ethereum",
    "network": "Mainnet"
  },
  "block_identifier": {
    "index": 0
  }
}'

Response:

{
    "block":{
        "block_identifier":{
            "index":0,
            "hash":"0xd4e56740f876aef8c010b86a40d5f56745a118d0906a34e69aec8c0db1cb8fa3"
        },
        "parent_block_identifier":{
            "index":0,
            "hash":"0xd4e56740f876aef8c010b86a40d5f56745a118d0906a34e69aec8c0db1cb8fa3"
        },
        "timestamp":0,
        "transactions":[
            {
                "transaction_identifier":{
                    "hash":"0xd4e56740f876aef8c010b86a40d5f56745a118d0906a34e69aec8c0db1cb8fa3"
                },
                "operations":[
                    {
                        "operation_identifier":{
                            "index":0
                        },
                        "type":"MINER_REWARD",
                        "status":"SUCCESS",
                        "account":{
                            "address":"0x0000000000000000000000000000000000000000"
                        },
                        "amount":{
                            "value":"5000000000000000000",
                            "currency":{
                                "symbol":"ETH",
                                "decimals":18
                            }
                        }
                    }
                ]
            }
        ]
    }
}

I checked the go-ethereum implementation where it calculate the rewards and it doesn't have any special treatment for block zero: https://github.com/ethereum/go-ethereum/blob/045e90c8971cddbabeac0abd54240cf02bc1d94d/consensus/ethash/consensus.go#L646-L653

Open questions

Is there a way to test this with a unit test? Would it be nice to add one for this case?

[shrimalmadhur]

@thepabloaguilar This is great, thanks for solving it quickly. I think you could try adding a test like https://github.com/coinbase/rosetta-ethereum/blob/master/ethereum/client_test.go#L1173 - you can create a test like TestBlock_Genesis - you can look some block specific test where you can download the block result as json and mock it. Let me know if that doesn't make sense.

[thepabloaguilar]

@shrimalmadhur I've wrote a test, I think it's make sense to have that test because we're talking about the first block on the chain