Contract interactions not supported on Weight V2 chains

[DamianStraszak]

First of all -- huge kudos for developing this library -- it's absolutely great, I have been using it quite a lot.

As for the issue I encountered. It seems to me that the support for WeightsV2 is not there yet for Smart Contracts (ContractInstance and related classes). In particular the example https://github.com/polkascan/py-substrate-interface/blob/master/examples/create_and_exec_contract.py does not work on WeightsV2 chains.

I have dug into it a little, and it seems that's because in places like https://github.com/polkascan/py-substrate-interface/blob/1f558e6a5fa9a1ea71ae25211989ebf858a14075/substrateinterface/contracts.py#L772 or more specifically https://github.com/polkascan/py-substrate-interface/blob/1f558e6a5fa9a1ea71ae25211989ebf858a14075/substrateinterface/contracts.py#L797 there is still a one-dimensional gas_limit.

Changing this unfortunately does not fix the problem, there is something else to fix also -- which I haven't figured out yet.

The question is whether there is a plan to add this support? My two comments here:

• I think it's fine to drop the compatibility with WeightsV1 for Contracts, because there will never be a chain that launches Contracts on the old Weights. Currently the only production chains that have contracts are Aleph Zero and Astar, both on WeightsV2
• I can try sending you a PR with the fix for this issue once I figure out what all needs to be done. But in such a case, there might be some work required for a reviewer on your side to help me bring it to an acceptable form, as I'm not python-native :P

[arjanz]

Thanks for the compliment :)

I haven't given the contract interface much attention recently, so this would be a good opportunity to update to the latest specs of the contracts pallet.

Dropping WeightV1 support is a good one. If there are no production chains atm using it and therefor no one will in the future, that will make things a lot easier.

I will have a look to see what the exact issues are. Do you have an test endpoint (or otherwise Docker image) where I can test the version of the contract pallet you are using?

[DamianStraszak]

Thanks for a quick response!

You can use Aleph Zero testnet: wss://ws.test.azero.dev (https://polkadot.js.org/apps/?rpc=wss%3A%2F%2Fws.test.azero.dev#/explorer). Currently Alice has funds there, but in case someone takes them here is a faucet https://faucet.test.azero.dev/

The version of pallet contracts that production chains currently use is substrate polkadot-v0.9.38 https://github.com/paritytech/substrate/tree/polkadot-v0.9.38 -- you can alternatively build and run a substrate node from this branch.

[arjanz]

I ran some tests, my findings:

• There is a check for WeightV2, but too naive. It just convert the old int version to {'ref_time': gas_limit, 'proof_size': 0}.
• In current example (create_and_exec_contract.py) this will lead to Exception {'code': 1010, 'message': 'Invalid Transaction', 'data': 'Transaction would exhaust the block limits'}, because of a too high ref_time and no proof_size.
• When I hard-code here the numbers generated by PolkadotJS:

to {'ref_time': 25990000000, 'proof_size': 11990383647911208550}, I can successfully deploy. But then also run into problems with the ContractsApi.call runtime call.

So basically I will have to:

• Refactor the whole contract interface and drop the old contract support.
• This will include to determine the correct WeightV2 values (examine how PolkadotJS does this).
• Debug and fix SCALE decoding issues with the ContractsApi.call runtime call. This is likely due to type mismatch; types in runtime APIs still need manual administration. These types will be included in the future, when Parity releases MetadataV15.

This will be quitte some work, I think I can start somewhere this week, but it will probably take at least a week before this is available.

[DamianStraszak]

Thanks for working on this! If I can be of any help -- testing stuff, or review, then let me know.

I'm also eagerly awaiting metadata V15 -- will be really useful for libraries like this one.

[arjanz]

I'm working on a PR, for now I have a workaround to read and exec contract methods, until the new release. Add the following type registry override to the init:

substrate = SubstrateInterface(
        url="wss://ws.test.azero.dev",
        type_registry={
            "types": {
                "ContractExecResult": "ContractExecResultTo267"
            }
        }
    )

[arjanz]

Released: https://github.com/polkascan/py-substrate-interface/releases/tag/v1.7.0