mf2

Unicode MessageFormat 2 for Rust applications — web applications with Leptos, and native command-line and terminal applications. mf2 is the one crate an application's code names. It defines what a tr! call site builds (Tr, TrArgs, TrRich, ArgValue), carries the Leptos layer as mf2::leptos, a native application's catalogs and locale as mf2::native and a terminal UI's text as mf2::ratatui, re-exports the formatter of the Rust MF2 crates, and carries the feature flags that choose what a build includes: the Leptos line (leptos for 0.9, leptos-0-8) and mode (ssr, hydrate or csr), a native application (native) and its Ratatui text (ratatui), localized numbers (fn-number), dates (fn-datetime and a backend), the host (host-std natively, host-web in the browser), and compile_str for an ad-hoc message.

Messages are written in MF2, checked when the application compiles, and compiled to one small binary catalog per language. On the web, the browser loads a language's catalog when it needs it, and the client wasm contains none of the text.

An application's translation crate depends on mf2 and, as a build dependency, mf2-build. A web application's server turns on axum; a native one turns on native, and for a terminal UI ratatui. 1.x's leptos-mf2 and mf2-axum are these features now (mf2::leptos, mf2::axum). For native applications mf2 also provides Corpus, the one value a native build generates, and Message, which formats any tr! call site outside Leptos.

API documentation: https://docs.rs/mf2.

The Rust MF2 book is the user guide.

Versions: every Rust MF2 crate is released together, and 1.x keeps the promise the book's versioning chapter states; the minimum Rust version is 1.88.

License

MIT (LICENSE) for the code. src/matching/cldr.rs, the locale matcher's table, is derived from the Unicode CLDR and is under the Unicode License v3 (LICENSE-UNICODE); the package's licence is MIT AND Unicode-3.0.