es-fluent

The public facade for typed Project Fluent messages in Rust. It re-exports the derive macros and runtime traits used by es-fluent manager integrations.

Add the facade

[dependencies]
es-fluent = "*"

Derive a typed message in a library target:

use es_fluent::EsFluent;

#[derive(EsFluent)]
pub enum LoginMessage<'a> {
    Welcome { name: &'a str },
    SignedOut,
}

The CLI generates message IDs and Fluent arguments from the type:

login_message-Welcome = Welcome, { $name }!
login_message-SignedOut = You are signed out.

Resolve values through a concrete embedded, Dioxus, or Bevy manager:

let text = i18n.localize_message(&LoginMessage::Welcome { name: "Ada" });

Derive surface

• EsFluent defines messages and can infer selector values for unit-only enums.
• EsFluentVariants generates localizable field or variant metadata.
• EsFluentLabel defines a type-level label.
• EsFluentChoice defines standalone selector values.

Features icu-datetime, chrono, and jiff support localized temporal arguments for their matching types.

Missing-message policy

Configured crates validate derived messages against the fallback locale during compilation. Call es_fluent_build::track_i18n_assets() from Cargo's selected custom-build target so the compiler can read the generated fallback catalog. A missing message value is a source-spanned compile-time error naming the Rust item, domain, fallback root, and recovery command by default.

Set the package-local policy when the application must keep rendering after every locale and Fluent fallback is exhausted:

# i18n.toml
missing_message_policy = "fallback-str"

strict is the default. Strict and fallback-string packages can coexist in the same workspace build.

localize_message(...) and localize_label(...) then return the derived Rust source name in snake_case. Struct messages and labels use the type name, enum messages use the variant name, and EsFluentVariants messages use the source field or variant name. Fallible try_localize_message(...) and try_localize_label(...) continue to return None for missing output.

See the derive guide for attributes, generated FTL, domains, namespaces, choices, and labels. See the getting-started tutorial for CLI and runtime setup.