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Frontend migration

polkadot-js

  • Bump @polkadot dependencies to latest.
  • Add "@polkadot/util": "^10.2.3" - required for WeightV2.

Gas limit estimation

The following snippet is shortened and simplified call for gas estimation:

export const getGasLimit = async (
  api: ApiPromise,
  userAddress: string,
  message: string,
  contract: ContractPromise,
  options = {} as ContractOptions,
  args = [] as unknown[]
): Promise<WeightV2 | string> => {
  const abiMessage = contract.abi.messages.find((m) => m.method === message);
  if (!abiMessage) { 
    // Error case. Needs proper handling
    return `"${message}" not found in Contract`;
  }

  const { value, gasLimit, storageDepositLimit } = options;

  const result = await api.call.contractsApi.call<ContractInstantiateResult>(
    userAddress,
    contract.address,
    value ?? new BN(0),
    gasLimit ?? null,
    storageDepositLimit ?? null,
    abiMessage.value.toU8a(args)
  );

  return result.gasRequired;
};

And on the call-side:

const gasLimit = await getGasLimit(api, loggedUserAddress, contract_method, contract, options, args);
// Now, we can use the estimated `gasLimit` in actual call below.
await contract.tx.contract_method( { gasLimit });

Please not that the example usage above is not working and is used only for presenting the case and should not be copied.

Code above has been updated from the paritytech/ink-workshop repository.

Weight V2

Ink4 introduces big changes to weights. This has an effect on the frontend integrations where one has to specify gas limits of contract calls.

If you're already using dryRun functionality of the API to get the call estimate to use for later, you probably don't need to do any changes as the returned types here also changed to WeightV2.

If you are using hardcoded values for the gas limit, you need to replace the single dimension value with the following:

// New imports.
import type { WeightV2 } from '@polkadot/types/interfaces';
import { BN } from '@polkadot/util';

const gasLimit = api.registry.createType('WeightV2', {
    refTime: _contractCallRefTime_,
    proofSize: _contractCallProofSize_,
  }) as WeightV2;

where _contractCallRefTime_ and _contractCallProofSize_ are the estimated gas limits for the transaction. You can get the estimates using cargo contract or with https://contracts-ui.substrate.io/.

Call return type

New LangError has been added to all return types - this means that where previously users expected a value of type <T> they will now get either Err { ... } or Ok { value: T }. This has to be accounted for and handled where we query (read from) the blockchain.

Example (minimal) migration in getDataFromOutput and its usage.