stake-pool: Prefund split account during redelegate

[joncinque]

Problem

During redelegate, the first split account should have the rent-exempt reserve populated. This makes it clearer how many lamports are actually moving to the new validator.

Solution

Include the stake pool reserve in redelegate, and withdraw the required rent during redelegate.

[2501babe]

this case is probably not worth caring about but note it fails if the reserve is empty but the transient account is fully funded

[joncinque]

I see what you mean... the logic is really touchy around here. Note that the reserve shouldn't ever be empty, since it needs to have at least the rent-exemption to exist, so this line shouldn't ever trip unnecessarily.

I put this in because some later tests showed that I was accidentally drawing everything out of the reserve and destroying it, so the intent is to make sure that we don't delete the reserve ever.

How about this then?

if required_lamports_for_rent_exemption > 0 {
    if required_lamports_for_rent_exemption >= reserve_stake_info.lamports() {
        return Err(StakePoolError::ReserveDepleted.into());
    }
    Self::stake_withdraw(.....)?; 
}

[2501babe]

yes thats what i had in mind!

[2501babe]

iirc modifying the instruction like this is fine because it hasnt been deployed yet

[joncinque]

iirc modifying the instruction like this is fine because it hasnt been deployed yet

That's exactly right, thanks for double-checking!