Proposal: Error handling specification #1

Hi all,

I am working on a project that validates whether four Ethereum client implementations (Geth, Erigon, Nethermind, Besu) behave consistently to one another.

And while doing the experiments, I found out that the clients handle error cases in very much different ways:

----------------------------------------------------------------------------------

1. Invalid block argument to `getBlockTransactionCount`
- (Geth, Erigon, Besu) returns `null`
- (Nethermind) returns an `Error`

2. Invalid block argument to `getPastLogs`
- (Geth, Erigon, Besu) returns `[]`
- (Nethermind) returns an `Error`

3. Invalid block argument to `getTransactionFromBlock`
- (Geth, Erigon, Besu) returns `null`
- (Nethermind) returns an `Error`

4. Invalid block argument to `getBlockUncleCount`
- (Geth, Erigon, Besu) returns `null`
- (Nethermind) returns an `Error`

5. Invalid block argument to `getUncle`
- (Geth, Erigon, Besu) returns `null`
- (Nethermind) returns an `Error`

6. Invalid block argument to `getCode` (1)
- (Geth, Nethermind, Besu) returns an `Error`
- (Erigon) returns the code of the address

7. Invalid block argument to `getCode` (2)
- (Geth, Erigon, Nethermind) returns an `Error`
- (Besu) returns `null`

8. Invalid block argument to `getBalance`
- (Geth, Erigon, Nethermind) returns an `Error`
- (Besu) returns `null`

9. Invalid block argument to `getTransactionCount`
- (Geth, Erigon, Nethermind) returns an `Error`
- (Besu) returns `0`

10. Invalid block argument to `getStorageAt`
- (Geth, Erigon, Nethermind) returns an `Error`
- (Besu) returns `null`

----------------------------------------------------------------------------------

11. Unknown account to `getProof`
- (Geth, Nethermind) returns an account object
- (Besu) returns an `Error`
- Note: Erigon does not support `eth_getProof`

----------------------------------------------------------------------------------

12. Wrong range to `getPastLogs`
- (Geth, Besu) returns `[]`
- (Erigon, Nethermind) returns an `Error`

13. Wrong range to `getFeeHistory`
- (Geth, Erigon) returns `{ "oldestBlock": "0x0", "gasUsedRatio": null }`
- (Nethermind, Besu) returns an `Error`

----------------------------------------------------------------------------------

14. Invalid index to `getTransactionFromBlock`
- (Geth, Erigon, Besu) returns `null`
- (Nethermind) returns an `Error`

15. Invalid index to `getUncle`
- (Geth, Erigon, Besu) returns `null`
- (Nethermind) returns an `Error`

I assume these discrepancies derived from the lack of error handling specification in this document. So, how about specifying the expected results (e.g., Error, null, 0, [ ], ...) so that different client implementations behave consistently in error cases as well?

Example test cases can be found in the following link: [https://github.com/JosephK95/RPCTests](url)

Thanks and please let me know if there is anything I can help you with.