Allow setting a default dataSuffix when using createWalletClient

[dgca]

TL;DR: Proposal to add dataSuffix param to createWalletClient to easily add a data suffix to all transactions.

---

Hey all, the relatively new ERC-8021 spec which the ox library already has support for (thank you) defines a new dataSuffix capability that wallets can choose to support.

This dataSuffix capability can be used to add ERC-8021 attribution to wallet_sendCalls requests.

Since builders will often just have one builder code they want to attach to all transactions, it would be nice to be able to set that up once, rather than have to add that to every transaction.

My recommendation for how to do this is to add a new dataSuffix config param to createWalletClient.

E.g.

import { createWalletClient, custom } from 'viem';
import { mainnet } from 'viem/chains';
import { Attribution } from 'ox/erc8021';
 
const myDataSuffix = Attribution.toDataSuffix({
  codes: ['foobarbaz']
});

type DataSuffixOptionType = `0x${string}` | {
  value: `0x${string}`;
  required: boolean;
};

const client = createWalletClient({
  chain: mainnet,
  transport: custom(window.ethereum!),
  dataSuffix: {
    value: myDataSuffix,
    required: false
  } satisfies DataSuffixType
});

If a user adds this dataSuffix field, transactions submitted from this client would include the dataSuffix by default.

This would apply to both walletClient.sendTransaction and walletClient.sendCalls.

• walletClient.sendTransaction would essentially do the same thing that writeContract's dataSuffix option does.
• walletClient.sendCalls would automatically add the dataSuffix capability to the transaction
• Both of these could let the developer override the dataSuffix by passing in a different value when actually submitting a transaction

The value of dataSuffix is typed like this:

type DataSuffixOptionType = `0x${string}` | {
  value: `0x${string}`;
  required: boolean;
};

The intended behavior is that if a hex string is used or if required is false, when the dataSuffix capability is passed to a wallet_sendCalls call, it must be marked as optional.

Only when required is true should the capability's optional field be false.

Alternatives considered

Originally I was going to suggest adding a defaultCapabilities param to be able to be able to set defaults any capability (e.g. the paymaster capability could benefit from a default), but decided against it as this wouldn't extend to walletClient.sendTransaction (or at least, the interface is awkward since capabilities don't apply to eth_sendTransaction).

E.g.

import { createWalletClient, custom } from 'viem';
import { mainnet } from 'viem/chains';
import { Attribution } from 'ox/erc8021';
 
const myDataSuffix = Attribution.toDataSuffix({
  codes: ['foobarbaz']
});

const client = createWalletClient({
  chain: mainnet,
  transport: custom(window.ethereum!),
  defaultCapabilities: {
    dataSuffix: {
      value: myDataSuffix,
      optional: true
    }
  }
});

FWIW, I could be convinced that this is a better interface. defaultCapabilities.dataSuffix could be treated as a special case so it applies to walletClient.sendTransaction as well.

Support

I'd be happy to implement this if y'all are open to it, and would likewise be totally okay if someone else did the work. If it's accepted, lmk if you want me to take a stab at it.

Wagmi implications

If this proposal is accepted, we can talk about extending this functionality to wagmi (likely as a param to createWagmiConfig).

[dgca]

Implemented in viem@4.25.0