signer: enable typed data signing from signer rpc

[nasdf]

Hello,

This PR should make it easier to sign EIP-712 typed data from the accounts.Wallet API.

var wallet accounts.Wallet
var account accounts.Account
var typedData signer.TypedData

data, _ := json.Marshal(typedData)

wallet.SignData(account, accounts.MimetypeTypedData, data)

[holiman]

Not sure I follow. Why can't you use this existing method?

func (api *SignerAPI) SignTypedData(ctx context.Context, addr common.MixedcaseAddress, typedData TypedData) (hexutil.Bytes, error) {
	signature, _, err := api.signTypedData(ctx, addr, typedData, nil)
	return signature, err
}

[holiman]

Ah, ok, it's not available on the interface. So then I think you could still avoid all the copy-paste code, and just call that method from inside the switch... ?

[nasdf]

Ah, ok, it's not available on the interface. So then I think you could still avoid all the copy-paste code, and just call that method from inside the switch... ?

That would be a much better approach but determineSignatureFormat is expecting a SignDataRequest return value.
If you think a better approach is to add it to the wallet interface I'd be happy to try that route instead.

[holiman]

We already have SignGnosisSafeTx, isn't that basically the same thing?

[nasdf]

We already have SignGnosisSafeTx, isn't that basically the same thing?

It does do something similar, but the goal of this PR is to make meta transactions possible from the accounts.Wallet interface.

As a user of go-ethereum as a library there’s currently no straightforward way to sign meta transactions in a generic way that would work with key stores, ledger, etc.

[holiman]

Superseded by #26241