Derive attributes

zestors has four derives, all in zestors::prelude:

Derive	On	Implements
`Message`	a struct or enum	`Message`: fire-and-forget, or with a reply
`Interface`	an enum of `Envelope<M>` variants	`Interface`: the set of messages an actor accepts
`HandlerInterface`	the same enum	dispatch from the interface to a `Handler`’s `Handle<M>` impls
`StableId`	a message	`StableId`: the message’s id on the wire, for remote messages

Each derive reads its options from #[msg(...)] and #[zestors(...)] attributes. The two are interchangeable.

Key	Used by	Meaning
`reply = T`	`Message`	The message expects a reply of type `T`. Without it, the message is fire-and-forget.
`id = "<uuid>"`	`StableId`	The message’s `MessageId`. Required; leave it out and the compile error suggests one.
`no_auto_register`	`StableId`	Leave the message out of `ClusterConfig::auto_register`.
`interface_path = "path"`	`Message`, `Interface`	Where the generated code finds `zestors-interface`. Default `::zestors::interface`.
`actor_path = "path"`	`HandlerInterface`	Where it finds `zestors-actor`. Default `::zestors::actor`.
`distr_path = "path"`	`StableId`	Where it finds `zestors-distr`. Default `::zestors::distr`.

A remote message usually combines both keys in one attribute:

use serde::{Deserialize, Serialize};
use zestors::interface::Message;
use zestors::prelude::*;

#[derive(Message, StableId, Serialize, Deserialize, Debug)]
#[msg(reply = "Vec<u8>", id = "4f9e5a8b-7c6d-4e3f-8a1b-2c3d4e5f6a7b")]
struct Read {
    path: String,
}

A few details:

Quote reply types that contain <: reply = "Option<String>". A plain path such as reply = u32 needs no quotes.
The path keys are only needed when you depend on the sub-crates directly instead of on zestors. For example, with zestors-interface on its own: #[zestors(interface_path = "zestors_interface")].
HandlerInterface generates code that names rootcause::Report, so the crate using it must depend on rootcause.
Interface only works on enums whose variants each hold exactly one Envelope<M>, and doesn’t support generics. Message does support generic types.
StableId on a generic type is never auto-registered. Register each concrete type with ClusterConfig::register.

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Derive attributes