authz: if grantee doesn't exist, should create account

[cmwaters]

Summary

If the grantee of an authorization doesn't exist, create a new account.

Problem Definition

I was playing with the new authz module. Specifically, I wanted to create a new account and give it access to vote on behalf of my main account. The authorization worked fine but when I tried to send a vote message with my new account, I couldn't because the account didn't exist. Instead I got:

Account does not exist on chain. Send some tokens there before trying to query sequence.

(this is a cosmjs error but it just means it tried to query auth and no account was returned)

Proposal

I'm not too sure what the current policy is on account creation (i.e. should all accounts need a non-zero token balance). If it's possible, I would propose that the authz module also checks if the grantee exists and if not creates the account. I guess there could be a problem with getting the new accounts PubKey. I would just prefer to have to not have to add some tokens to an account first.

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[cmwaters]

Ah it seems like we do a similar thing with feegrant

// create the account if it is not in account state
granteeAcc := k.authKeeper.GetAccount(ctx, grantee)
if granteeAcc == nil {
granteeAcc = k.authKeeper.NewAccountWithAddress(ctx, grantee)
    k.authKeeper.SetAccount(ctx, granteeAcc)
}

[alexanderbez]

Creating an account is fine IMO (assuming the granter is paying the fees). Also, an account doesn't need a non-zero balance to exist 👍

[amaury1093]

Sounds fine to me too.

I guess there could be a problem with getting the new accounts PubKey.

Not really a problem, just that in TXs that the grantee sends, they need to put a non-empty pub_key in this field. It's an optional field for accounts that already exist in state with an associated pubkey. But if we're creating an acct like in #10590 (comment), then the account's pubkey in state is nil.

[aaronc]

I think the workflow here would be to create a feegrant first which creates the account, then to create authorizations

[amaury1093]

From a client UX, my preference would still be that the SDK allows the steps (1) create authz and (2) create feegrant/send tokens to grantee, to be done in whichever order.

The downside i see is that this solution is API breaking (dep from x/authz on x/auth)