Instruction input wrappers to override account metas

[lorisleiva]

Currently, the generated instruction helpers make a lot of assumptions about account metas (as defined in the Codama IDL) that is impossible for the end-user to override. For instance, right now you cannot change the writable status of your instruction account.

Say I wanted to do this:

const ix = getTransferSolInstruction(tx, {
  source: createNoopSigner(address('1234')),
  destination: address('5678'),
});

But for some reason, I wanted to override the destination account to be a readonly account. Right now, I would need to deep copy the instruction in order to change that. However, if Codama accepted something like a asReadonly wrapper, it could become something like this:

const ix = getTransferSolInstruction(tx, {
  source: createNoopSigner(address('1234')),
  destination: asReadonly(address('5678')),
});

We can then take it one step further and have wrappers like asLookupMeta for accounts linked to LUTs.

const ix = getTransferSolInstruction(tx, {
  source: createNoopSigner(address('1234')),
  destination: asLookupMeta(
    address('5678'), /* real address */
    address('9999'), /* lookup address */
    7, /* lookup index */
  ),
});

Offering these extra building blocks could be interesting in the context of generated clients and would allow client users a lot more flexibility.

Under the hood, these wrapper functions could simply construct IAccountMeta type or equivalent. The Codama generated function would need to accept these types and treat them accordingly.