Feature Request: add pda realloc to account macro

[cavemanloverboy]

I think this new feature could go in the #[account()] macro, e.g.

#[derive(Accounts)]
#[instruction(new_size: usize)]
pub struct MyAccounts<'info> {
    #[account(
        mut,
        realloc = new_size,
        ...
    )]
    pub my_pda: Account<'info, DataAccount>
}

and perhaps skip the realloc if old size is equal to new size.

[cavemanloverboy]

If you point me to the right file/scope I'll see if I can throw something together

[callensm]

The implementation should also include the requirement of including something like exempter (similar to the payer input) to handle the transfer of lamports to or from the program account to manage the rent exemption increase or decrease related to the reallocation.

[armaniferrante]

@cavemanloverboy see https://github.com/project-serum/anchor/tree/master/lang/syn/src.