Anchor's `init_if_constraint` for the optional initialization of Accounts?

Question

We're using Anchor to build our Solana Programs. It's a great framework to keep the instruction logic separate from all the Account checks that we have to do.

I've recently started using the init_if_needed attribute to handle instructions where some Account initialization may be optional. We use an already initialized dummy account when the instruction should not initialize a new account, to avoid users paying unnecessary rent... The actual check whether a new account should be created is done within the program.

It works for our use case! It looks like something like this:

#[derive(Accounts)]
pub struct OurAccounts<'info> {
    // ...
    #[account(
        init_if_needed,
        payer = payer,
        space = OurAccount::SIZE,
        constraint = if condition ? { 
                account.key == dummy 
            } else { 
                account.key != dummy && !account.created 
            }
            @ OurError::ConstraintNotSatisfied,
    )]
    pub account: Account<'info, OurAccount>,
    // ...
}

However, init_if_needed is intended for another use case. -> it only runs if the account does not exist yet.

So we're sort of abusing this attribute to conditionally create new accounts. Also, we need to have a dummy account for this to work and share this account's address private key with our users. What we need, we think, would be called the init_if_constraint, where the init CPI to Solana's system program would be omitted if the constraint is not satisfied.

My question:

• Is there a better Anchor way to optionally init accounts within instructions?
• If not, is this easy to do with a Solana system CPI, within the Anchor environment?

Answer 1

There is a new feature coming in v26 which you probably would want to check out. https://github.com/coral-xyz/anchor/pull/2101 They're called optional accounts. It should allow you to just omit an account if you don't want it sometimes. The dummy account address used in this implementation of optional accounts is the program id itself.