NEO: clear LastGasPerVote when voting for NULL, fix #2894

[roman-khimov]

It's a rather trivial fix, but it needs some substantial testing wrt account balances (just comparing the state won't be enough). @superboyiii.

Type of change

• Bug fix (non-breaking change which fixes an issue)
• Breaking change (fix or feature that would cause existing functionality to not work as expected)

How Has This Been Tested?

• Unit tests

[vncoelho]

I remember this discussion some time ago. It seems to be ok.

[superboyiii]

I will

[shargon]

Seems good to me, just wait for @superboyiii

[superboyiii]

Although it will surely make some storage changes, but checked NEO and GAS balance on all mainnet existed account, no problem. So it should be safe.

[shargon]

Although it will surely make some storage changes, but checked NEO and GAS balance on all mainnet existed account, no problem. So it should be safe.

Did you checked?

[superboyiii]

Although it will surely make some storage changes, but checked NEO and GAS balance on all mainnet existed account, no problem. So it should be safe.

Did you checked?

Yes, I checked. Many storage changes there. But the same event log(checked some of these) and the same NEO and GAS balance(all existed addresses).

For example, in a tx: 0x38091b803f794e50dcc10a9091becaf4f65d35d3ef9e71cfa90c7936af50757e on block 39632 of mainnet,
Original Storage Changes:

{
    "block": 39632,
    "size": 7,
    "storage": [
        {
            "state": "Changed",
            "key": "\u002Bv///xQXVU6kNdnigqZEh4tAVHW\u002BNwA2AQ==",
            "value": "QQEhBCg32Dw="
        },
        {
            "state": "Changed",
            "key": "\u002Bv///ws=",
            "value": "68Z3AaV6Eg=="
        },
        {
            "state": "Changed",
            "key": "\u002Bv///xSPX4PVGdD5t8CX0nYRsTB3r0935Q==",
            "value": "QQEhBbkBXAAW"
        },
        {
            "state": "Changed",
            "key": "\u002B////xQXVU6kNdnigqZEh4tAVHW\u002BNwA2AQ==",
            "value": "QQQhAlEEIQPQmgAAIQfI7lv90/cA"
        },
        {
            "state": "Changed",
            "key": "\u002B////wE=",
            "value": "Riw0AQ=="
        },
        {
            "state": "Changed",
            "key": "\u002B////yED/QTemD9OBMlimrPPyD9BvnQxuWv4UqkYc8OMqPc37iw=",
            "value": "QQIgASEDKV8C"
        },
        {
            "state": "Changed",
            "key": "\u002Bv///xRjslsjaXYnEvQP2GT6JumaYZgBIw==",
            "value": "QQEhBeYy2gAW"
        }
    ]
}

In this PR:

{
    "block": 39632,
    "size": 7,
    "storage": [
        {
            "state": "Changed",
            "key": "\u002Bv///xQXVU6kNdnigqZEh4tAVHW\u002BNwA2AQ==",
            "value": "QQEhBCg32Dw="
        },
        {
            "state": "Changed",
            "key": "\u002Bv///ws=",
            "value": "68Z3AaV6Eg=="
        },
        {
            "state": "Changed",
            "key": "\u002Bv///xSPX4PVGdD5t8CX0nYRsTB3r0935Q==",
            "value": "QQEhBbkBXAAW"
        },
        {
            "state": "Changed",
            "key": "\u002B////xQXVU6kNdnigqZEh4tAVHW\u002BNwA2AQ==",
            "value": "QQQhAlEEIQPQmgAAIQA="
        },
        {
            "state": "Changed",
            "key": "\u002B////wE=",
            "value": "Riw0AQ=="
        },
        {
            "state": "Changed",
            "key": "\u002B////yED/QTemD9OBMlimrPPyD9BvnQxuWv4UqkYc8OMqPc37iw=",
            "value": "QQIgASEDKV8C"
        },
        {
            "state": "Changed",
            "key": "\u002Bv///xRjslsjaXYnEvQP2GT6JumaYZgBIw==",
            "value": "QQEhBeYy2gAW"
        }
    ]
}

So the differ is between the storage of key \u002B////xQXVU6kNdnigqZEh4tAVHW\u002BNwA2AQ==
Original: QQQhAlEEIQPQmgAAIQfI7lv90/cA
VS
this PR: QQQhAlEEIQPQmgAAIQA=

But not sure what's stored in this key, could you help me check what's in this storage? @shargon

[roman-khimov]

Exactly as expected, it's LastGasPerVote that's not going to be used (because account doesn't vote). So we store 0 (short) instead of something (more bytes).