Allow updating the generated program address

[stegaBOB]

Currently, the program address is generated as a const with a typed Address for the default key. There is no way to update this value. Some programs use separate addresses for local development/devnet vs mainnet. Currently those programs would need a copy of the generated clients for each cluster.

One potential solution could be to export let {program id} = "key" as Address and provide a setter to allow users to update the id. That would be a very simple change to the program template:

export let {{ programAddressConstant }} = '{{ program.publicKey }}' as Address;

export function {{ setProgramAddressFucntion }} (address: Address) {
  {{ programAddressConstant }} = address;
}

[lorisleiva]

Ew module variables? Straight to jail! Haha jk but this introduces module side effects and removes tree-shakability so we tend to avoid them in JS libraries. However, if we had that information on the Codama IDL — say a map of address overrides for various clusters — then we could generate multiple constants. However, unlike Umi that uses a context object to store shared knowledge, Solana Kit is fully functional and it makes the idea of "switching" clusters something that lands more on the application layer than the program library layer.

[stegaBOB]

I'll admit it didn't feel great doing that haha. Ideally the default program id can be configurable on the client side though without requiring creating a new package each time IMO. I'm not super familiar with JS bundling/performance under the hood. Do you see any way for that to be doable without having performance impacts?