# mf2
Unicode MessageFormat 2 for Rust applications — web applications with
[Leptos](https://leptos.dev), 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`](https://docs.rs/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](https://evancarroll.github.io/rust-mf2/) is the user guide.
Versions: every Rust MF2 crate is released together, and 1.x keeps the
promise [the book's versioning chapter](https://evancarroll.github.io/rust-mf2/versioning.html) 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`.