RFC: Standardising how smart contracts expose state

[akhilesh.singhania]

@jzxchiang

Is the only benefit of making a replicated query call that it’s more safe? For example, certificate (or certified variable) validation wouldn’t be necessary.

Replicated queries are essentially calling https://sdk.dfinity.org/docs/interface-spec/index.html#http-query via an ingress message. If you called it as a query, you do not have any certification that you can validate. But if you call it as an ingress message, you get the result in the ingress status (via read_state) for which you now have a certification.

@jzxchiang

Separate question: why was the original canister_status callable only by the controller? This proposal will make it so any canister’s controller is publicly readable information, IIUC. I wonder if there was any good reason for the original restriction, which this proposal will remove.

canister_status returns private information about the canister. This is information that the canister does not want to expose to the rest of the world only to its controllers. The set of canister’s controllers has always been public. This proposal is not attempting to change any restrictions. The public data will remain public and the private data will remain private.

@nomeata

Actually, if you return no certificate, there is no need for the hash tree to have a certain root node. Therefore no need to have any pruned tree nodes. In other words, you can just create a fresh tree consisting of just the requested data.

Precisely, thanks for stating clearly what I meant to say in the original proposal.

@nomeata

But at this point the question is: why even return an unwieldy data structure like a hash tree when there is no certification around? Why not something more easier to digest, like Candid?

Indeed, this is the usual point on which we keep getting stuck.

I suppose, conceptually, what the proposal is suggesting is that read_state return the following struct:

(HashTree, Option<Certificate>. The hash tree is always returned and when executing as a non-replicated call, then the certificate is additionally returned.

Instead would something like the following make sense?

Result<CandidStruct, (HashTree, Certificate)>. Now when executing a replicated call, you get an easier to digest struct and when executing a non-replicated call, you get the HashTree and the certificate.