How to ensure account passed to anchor is readonly but initialized

Question

So just wanted a confirmation, i know init will check this and if its initialized it will error out, but what is the opposite of init check, i.e check the account passed is initialized ? does anchor automatically checks for initialization, if the type of the account is not AccountInfo but in form of the Account<'info,T> wrapper ? so if i do

``` 
#[derive(Accounts)
pub struct check<'info> {
test_initialization : Account<'info,test>
}
#[account]
pub test {
x : u32;
}```

can my program assume the account "test_initialization" was initialized in the above code snippet if it reaches the business logic side of it ?

Answer 1

There's no explicit check needed here. As long as there's no init, zero or zero_copy attribute for the account, the validator expects it to have been created. The answer to your question is yes, the program assumes the account is initialized and infact throws an error if it isn't.

Answer 2

It depends on what you mean by "initialised".

AccountInfo is, for all intent and purposes, unchecked. When using the Account wrapper though, the following gets checked:

• Check that the account has some lamports. Otherwise, throw AccountNotInitialized.
• Check if the account discriminator in the first 8 bytes of account data exists and matches the program. Otherwise, throw AccountDiscriminatorNotFound and AccountDiscriminatorMismatch respectively.
• Finally, parse the account using AnchorDeserialize::deserialize. If failed, throw AccountDidNotDeserialize

Most of this logic is sprinkled around these parts of the source code if you want to dig deeper:

• https://github.com/coral-xyz/anchor/blob/master/lang/src/accounts
• https://github.com/coral-xyz/anchor/tree/master/lang/attribute/account/src

Answer 3

In general Anchor assumes it's initialized, if you're using UncheckedAccount or similar , can use the following. (unless init is provided)

pub fn assert_initialized<T: Pack + IsInitialized>(
    account_info: &AccountInfo,
) -> Result<T, ProgramError> {
    let account: T = T::unpack_unchecked(&account_info.data.borrow())?;
    if !account.is_initialized() {
        Err(ErrorCode::UninitializedAccount.into())
    } else {
        Ok(account)
    }
}

Lifted off:

https://github.com/metaplex-foundation/metaplex-program-library/blob/e057c72645b32a5b3776a6a93e33440e719a0ddd/auction-house/program/src/utils.rs#L249-L256