Trait Upgrader 

pub trait Upgrader {
    // Required methods
    fn upgrade(&self) -> Result<Box<dyn Upgrader>, UpgraderError>;
    fn as_any(&self) -> &dyn Any;

    // Provided method
    fn is_terminal(&self) -> bool { ... }
}

A versioned config that upgrades itself one step toward the latest schema version. The latest version’s upgrade is a no-op that returns the receiver unchanged, which is how the upgrade walker detects completion.

Unlike the Go Upgrade(log *slog.Logger) (Upgrader, error), which can return the exact same pointer to signal termination, Rust’s ownership rules make returning “the same object” from &self awkward with a Box<dyn Upgrader> return type. The real implementation will need to settle this (e.g. via an enum of known versions, or an is_terminal() query) rather than pointer identity; see PORT_NOTES.md.

Required Methods

fn upgrade(&self) -> Result<Box<dyn Upgrader>, UpgraderError>

fn as_any(&self) -> &dyn Any

Exposes self as &dyn Any, so a caller holding a Box<dyn Upgrader> at the end of an upgrade walk can downcast back to the concrete type it expects — the Rust equivalent of the Go original’s upgraded.(*latest.CaproniConfig) type assertion, since Rust trait objects need an explicit escape hatch (there is no built-in upcast from dyn Upgrader to dyn Any without this).

Provided Methods

fn is_terminal(&self) -> bool

Reports whether this value is already at the latest version, i.e. whether upgrade would be a no-op. This is the termination signal config::registry::walk uses instead of the Go original’s pointer-identity check (next == cfg): Rust’s Box<dyn Upgrader> return type has no equivalent “return the same object” signal, so the walker asks each value directly rather than comparing addresses. Defaults to false; only the latest version’s Upgrader impl overrides it.

Dyn Compatibility

This trait is dyn compatible.

In older versions of Rust, dyn compatibility was called "object safety".

Implementors

impl Upgrader for CaproniConfig