ABIv2 tuple encoding is not supported

• Version: 4.7.1
• Python: 3.6
• OS: osx/linux/win

What was wrong?

ABIv2 tuple encoding is not supported, even though the currently used version of eth_abi does support these sort of encodings if invoked correctly. For this reason it is impossible to call the getOrderInfo() method (https://github.com/0xProject/0x-monorepo/blob/development/packages/migrations/artifacts/2.0.0/Exchange.json#L1370) from the 0x V2 Exchange contract. And many other methods as well.

The exception thrown is ValueError: No matching entries for 'tuple' in encoder registry.

[pipermerriam]

Somewhat duplicate of #829

This is implemented in eth-abi but full support hasn't been implemented in web3.

[MatthiasLohr]

Any news on this?

[fselmo]

@MatthiasLohr this open issue may have already been addressed by #1235 as mentioned in the closed duplicate issue linked above. @kclowes @marcgarreau any context I may be missing that warrants keeping this open?

[kclowes]

AFAICT this can be closed, but @MatthiasLohr do you have an example that isn't working?

[MatthiasLohr]

I'm not sure. I have something which isn't working, but not completely sure who is the culprit.

I have the following nested Solidity structure (from the perun project) and a binary encoding method for it:

struct State {
    bytes32 channelID;
    uint64 version;
    Allocation outcome;
    bytes appData;
    bool isFinal;
}

struct Allocation {
    address[] assets;
    uint256[][] balances;
    SubAlloc[] locked;
}

struct SubAlloc {
    bytes32 ID;
    uint256[] balances;
    uint16[] indexMap;
}

function encodeState(State memory state) public pure returns (bytes memory)  {
  return abi.encode(state);
}

and its Python equivalent:

class ChannelState(NamedTuple):
    channel_id: bytes
    version: int
    outcome: Allocation
    app_data: bytes
    is_final: bool

    def abi_encode(self) -> bytes:
        return eth_abi.abi.encode_abi(
            [
                "(bytes32,uint64,(address[],uint256[][],(bytes32,uint256[],uint16[])[]),bytes,bool)"
            ],
            [tuple(self)],
        )

    def __iter__(self) -> Generator[Any, None, None]:
        yield self.channel_id
        yield self.version
        yield tuple(self.outcome)
        yield self.app_data
        yield self.is_final

class Allocation(NamedTuple):
    assets: List[ChecksumAddress] = []
    balances: List[List[int]] = [[]]
    locked: List[SubAllocation] = []

    def __iter__(self) -> Generator[Any, None, None]:
        yield self.assets
        yield self.balances
        yield [tuple(sub_alloc) for sub_alloc in self.locked]

class SubAllocation(NamedTuple):
    id: bytes
    balances: List[int] = []
    index_map: List[int] = []

Now, I can either invoke encodeState in the smart contract using web3 or I can do the encoding directly in Python using eth_abi.abi.encode_abi. I would expect to have the same results, but, for the following State object it doesn't work:

// non-working example
state = ChannelState(
    channel_id=generate_bytes(32),
    version=1,
    outcome=Allocation(),
    app_data=bytes(FileSaleState()),
    is_final=False,
)

test_web3_contract.functions.encodeState(tuple(state)).call()
// returns 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

channel_state.abi_encode()
// returns 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
// 32 times `0x00` more

Interestingly, if I do not have empty lists in the Allocation object, both encoding methods work:

// working example
state = ChannelState(
    channel_id=generate_bytes(32),
    version=999,
    outcome=Allocation(
        assets=[],
        balances=[[]],
        locked=[
            SubAllocation(id=generate_bytes(32), balances=[], index_map=[])
        ],
    ),
    app_data=b"abcdefg",
    is_final=False,
)

So, as I said before, not exactly sure why this is happening and who is the culprit (maybe it's me?). Searching for possible reasons for this behavior, I stumbled over this open issue. Maybe someone can help and show me the path to go.

[MatthiasLohr]

Any ideas?

[kclowes]

Thanks for the example and the bump @MatthiasLohr. It looks like this may be a bug in eth-abi, but also looks like you have a workaround? We need to get a few things out the door, but this is on my list to look at.

[MatthiasLohr]

Unfortunately, this workaround only works in a testbed for me, since I want to connect to an already existing smart contract, which does not have the encodingMethod public, it's internal only. So I really need a solution for this, but for now couldn't find any...

[kclowes]

Gotcha. And you can't use the "working example" you listed above passing the empty arrays?

// working example
state = ChannelState(
  channel_id=generate_bytes(32),
   version=999,
   outcome=Allocation(
       assets=[],
       balances=[[]],
       locked=[
           SubAllocation(id=generate_bytes(32), balances=[], index_map=[])
       ],
   ),
   app_data=b"abcdefg",
   is_final=False,
)

[MatthiasLohr]

Unfortunately not, another part in the smart contracts checks for length of the error to be zero for specific cases (https://github.com/hyperledger-labs/perun-eth-contracts/blob/main/contracts/Adjudicator.sol#L256).

[fselmo]

@MatthiasLohr I'm seeing state and channel_state in your example that didn't work. Could that perhaps be the issue? Where is channel_state defined?

[fselmo]

I also wonder if your SubAllocation default value should be an empty SubAllocation rather than an empty list.

edit: oops, nope, I read that wrong

[fselmo]

This seems like a separate issue altogether (@MatthiasLohr), if you are still having issues here would you mind opening a new issue with a good description of what you are seeing and some code to duplicate?

I am going to close this as I believe it has been taken care of by #2211... but if that did not solve the issue please try to open this issue back up @Reverendus and / or update here if you still have issues.