Logging (id_effect_logger)

Workspace crate id_effect_logger provides an injectable EffectLogger service: log lines are effect steps that read the logger capability from R, so formatting and sinks stay composable and testable.

Usage shape

• ~EffectLogger inside effect! (with |r|) to obtain the handle, then info, warn, … on static or dynamic messages (impl Into<Cow<'static, str>>).
• provide_effect_logger (and related constructors) build a ProviderSpec you pass to run_with / build_env.

#![allow(unused)]
fn main() {
use id_effect::{Effect, effect, caps, provide, run_with};

fn app() -> Effect<(), (), caps!(EffectLogger)> {
    effect!(|r| {
        let log = *~EffectLogger;
        ~ log.info("hello");
        ()
    })
}

run_with([provide!(TracingLoggerLive)], app())?;
}

Backends

The crate ships pipeline pieces such as structured JSON, tracing integration, and composite backends—see cargo doc -p id_effect_logger for LogBackend, JsonLogBackend, TracingLogBackend, CompositeLogBackend.

Relation to the rest of Part II

Logging is just another capability: same mental model as Capability services and Providing Services. Swap backends in tests via provide!(…) instead of silencing println!.

Further reading

• cargo doc --open -p id_effect_logger