Tracing

factorio-rs can lower the tracing crate’s level macros to colored game.print calls. There is no Rust tracing runtime in Factorio - this is compile-time lowering, the same idea as println!.

Enable the feature

In your mod Cargo.toml:

[dependencies]
factorio-rs = { version = "0.1.2", features = ["tracing"] }

That pulls in the tracing crate so macros type-check under cargo check.

The CLI lowers these macros by default (factorio-rs-cli feature tracing). If you built the CLI from source with --no-default-features, reinstall with defaults enabled:

cargo install factorio-rs-cli
# or from a checkout:
cargo install --path crates/factorio-rs-cli --force

Usage

factorio_rs::control_mod! {
    use factorio_rs::tracing;

    #[factorio_rs::event(OnSingleplayerInit)]
    pub fn on_singleplayer_init() {
        tracing::info!("Hello factorio-rs!");
        let item = "iron-plate";
        tracing::warn!("missing {item}");
        tracing::error!("Oopsies!");
    }
}

With the feature enabled, factorio_rs::prelude::* also re-exports info!, warn!, error!, debug!, and trace!, so bare info!("...") works after use factorio_rs::prelude::*.

Supported paths:

Form	Example
Qualified	`tracing::info!("...")`, `factorio_rs::tracing::warn!("...")`
Bare (feature on)	`info!("...")` after importing the macro

What it emits

Each call becomes game.print with a level prefix and a PrintSettings color:

game.print("[INFO] Hello factorio-rs!", { color = { r = 0.55, g = 0.85, b = 1, a = 1 } })
game.print("[ERROR] Oopsies!", { color = { r = 1, g = 0.25, b = 0.25, a = 1 } })

Macro	Prefix	Color (approx.)
`error!`	`[ERROR]`	Red
`warn!`	`[WARN]`	Amber
`info!`	`[INFO]`	Light blue
`debug!`	`[DEBUG]`	Gray
`trace!`	`[TRACE]`	Darker gray

Format strings

Same subset as println! / format!:

{}, {0}, {name}
{{ / }} escapes
Format specs after : (e.g. {:.2}) are ignored

Not supported: structured fields (info!(foo = 1, "hi")), target:, spans, or runtime level filtering. Every lowered call always prints in-game.

Features (summary)

Crate	Feature	Purpose
`factorio-rs`	`tracing`	Optional `tracing` dependency + prelude re-exports for type-checking
`factorio-rs-cli`	`tracing` (default)	Enable frontend lowering when building mods
`factorio-frontend`	`tracing`	Implementation of the macro lowering