fluent_templates/

lib.rs

//! # Fluent Templates: A High level Fluent API.
//!
//! `fluent-templates` lets you to easily integrate Fluent localisation into
//! your Rust application or library. It does this by providing a high level
//! "loader" API that loads fluent strings based on simple language negotiation,
//! and the `FluentLoader` struct which is a `Loader` agnostic container type
//! that comes with optional trait implementations for popular templating
//! engines such as handlebars or tera that allow you to be able to use your
//! localisations in your templates with no boilerplate.
//!
//! ## Loaders
//! Currently this crate provides two different kinds of loaders that cover two
//! main use cases.
//!
//! - [`static_loader!`] — A procedural macro that loads your fluent resources
//!   at *compile-time* into your binary and creates a new [`StaticLoader`]
//!   static variable that allows you to access the localisations.
//!   `static_loader!` is most useful when you want to localise your
//!   application and want to ship your fluent resources with your binary.
//!
//! - [`ArcLoader`] — A struct that loads your fluent resources at *run-time*
//!   using `Arc` as its backing storage. `ArcLoader` is most useful for when
//!   you want to be able to change and/or update localisations at run-time, or
//!   if you're writing a developer tool that wants to provide fluent
//!   localisation in your own application such as a static site generator.
//!
//!
//! ## `static_loader!`
//! The easiest way to use `fluent-templates` is to use the [`static_loader!`]
//! procedural macro that will create a new [`StaticLoader`] static variable.
//!
//! ### Basic Example
//! ```
//! fluent_templates::static_loader! {
//!     // Declare our `StaticLoader` named `LOCALES`.
//!     static LOCALES = {
//!         // The directory of localisations and fluent resources.
//!         locales: "./tests/locales",
//!         // The language to falback on if something is not present.
//!         fallback_language: "en-US",
//!         // Optional: A fluent resource that is shared with every locale.
//!         core_locales: "./tests/locales/core.ftl",
//!     };
//! }
//! # fn main() {}
//! ```
//!
//! ### Customise Example
//! You can also modify each `FluentBundle` on initialisation to be able to
//! change configuration or add resources from Rust.
//! ```
//! use std::sync::LazyLock;
//! use fluent_bundle::FluentResource;
//! use fluent_templates::static_loader;
//!
//! static_loader! {
//!     // Declare our `StaticLoader` named `LOCALES`.
//!     static LOCALES = {
//!         // The directory of localisations and fluent resources.
//!         locales: "./tests/locales",
//!         // The language to falback on if something is not present.
//!         fallback_language: "en-US",
//!         // Optional: A fluent resource that is shared with every locale.
//!         core_locales: "./tests/locales/core.ftl",
//!         // Optional: A function that is run over each fluent bundle.
//!         customise: |bundle| {
//!             // Since this will be called for each locale bundle and
//!             // `FluentResource`s need to be either `&'static` or behind an
//!             // `Arc` it's recommended you use lazily initialised
//!             // static variables.
//!             static CRATE_VERSION_FTL: LazyLock<FluentResource> = LazyLock::new(|| {
//!                 let ftl_string = String::from(
//!                     concat!("-crate-version = {}", env!("CARGO_PKG_VERSION"))
//!                 );
//!
//!                 FluentResource::try_new(ftl_string).unwrap()
//!             });
//!
//!             bundle.add_resource(&CRATE_VERSION_FTL);
//!         }
//!     };
//! }
//! # fn main() {}
//! ```
//!
//! ## Locales Directory
//! `fluent-templates` will collect all subdirectories that match a valid
//! [Unicode Language Identifier][uli] and bundle all fluent files found in
//! those directories and map those resources to the respective identifier.
//! `fluent-templates` will recurse through each language directory as needed
//! and will respect any `.gitignore` or `.ignore` files present.
//!
//! [uli]: https://docs.rs/unic-langid/0.9.0/unic_langid/
//!
//! ### Example Layout
//! ```text
//! locales
//! ├── core.ftl
//! ├── en-US
//! │   └── main.ftl
//! ├── fr
//! │   └── main.ftl
//! ├── zh-CN
//! │   └── main.ftl
//! └── zh-TW
//!     └── main.ftl
//! ```
//!
//! ### Looking up fluent resources
//! You can use the [`Loader`] trait to `lookup` a given fluent resource, and
//! provide any additional arguments as needed with `lookup_with_args`. You
//! can also look up attributes by appending a `.` to the name of the message.
//!
//! #### Example
//! ```fluent
//!  # In `locales/en-US/main.ftl`
//!  hello-world = Hello World!
//!  greeting = Hello { $name }!
//!         .placeholder = Hello Friend!
//!
//!  # In `locales/fr/main.ftl`
//!  hello-world = Bonjour le monde!
//!  greeting = Bonjour { $name }!
//!         .placeholder = Salut l'ami!
//!
//!  # In `locales/de/main.ftl`
//!  hello-world = Hallo Welt!
//!  greeting = Hallo { $name }!
//!         .placeholder = Hallo Fruend!
//! ```
//!
//! ```
//! use std::{borrow::Cow, collections::HashMap};
//!
//! use unic_langid::{LanguageIdentifier, langid};
//! use fluent_templates::{Loader, static_loader};
//!
//!const US_ENGLISH: LanguageIdentifier = langid!("en-US");
//!const FRENCH: LanguageIdentifier = langid!("fr");
//!const GERMAN: LanguageIdentifier = langid!("de");
//!
//! static_loader! {
//!     static LOCALES = {
//!         locales: "./tests/locales",
//!         fallback_language: "en-US",
//!         // Removes unicode isolating marks around arguments, you typically
//!         // should only set to false when testing.
//!         customise: |bundle| bundle.set_use_isolating(false),
//!     };
//! }
//!
//! fn main() {
//!     assert_eq!("Hello World!", LOCALES.lookup(&US_ENGLISH, "hello-world"));
//!     assert_eq!("Bonjour le monde!", LOCALES.lookup(&FRENCH, "hello-world"));
//!     assert_eq!("Hallo Welt!", LOCALES.lookup(&GERMAN, "hello-world"));
//!
//!     assert_eq!("Hello World!", LOCALES.try_lookup(&US_ENGLISH, "hello-world").unwrap());
//!     assert_eq!("Bonjour le monde!", LOCALES.try_lookup(&FRENCH, "hello-world").unwrap());
//!     assert_eq!("Hallo Welt!", LOCALES.try_lookup(&GERMAN, "hello-world").unwrap());
//!
//!     let args = {
//!         let mut map = HashMap::new();
//!         map.insert(Cow::from("name"), "Alice".into());
//!         map
//!     };
//!
//!     assert_eq!("Hello Friend!", LOCALES.lookup(&US_ENGLISH, "greeting.placeholder"));
//!     assert_eq!("Hello Alice!", LOCALES.lookup_with_args(&US_ENGLISH, "greeting", &args));
//!     assert_eq!("Salut l'ami!", LOCALES.lookup(&FRENCH, "greeting.placeholder"));
//!     assert_eq!("Bonjour Alice!", LOCALES.lookup_with_args(&FRENCH, "greeting", &args));
//!     assert_eq!("Hallo Fruend!", LOCALES.lookup(&GERMAN, "greeting.placeholder"));
//!     assert_eq!("Hallo Alice!", LOCALES.lookup_with_args(&GERMAN, "greeting", &args));
//!
//!     assert_eq!("Hello Friend!", LOCALES.try_lookup(&US_ENGLISH, "greeting.placeholder").unwrap());
//!     assert_eq!("Hello Alice!", LOCALES.try_lookup_with_args(&US_ENGLISH, "greeting", &args).unwrap());
//!     assert_eq!("Salut l'ami!", LOCALES.try_lookup(&FRENCH, "greeting.placeholder").unwrap());
//!     assert_eq!("Bonjour Alice!", LOCALES.try_lookup_with_args(&FRENCH, "greeting", &args).unwrap());
//!     assert_eq!("Hallo Fruend!", LOCALES.try_lookup(&GERMAN, "greeting.placeholder").unwrap());
//!     assert_eq!("Hallo Alice!", LOCALES.try_lookup_with_args(&GERMAN, "greeting", &args).unwrap());
//!
//!
//!     let args = {
//!         let mut map = HashMap::new();
//!         map.insert(Cow::Borrowed("param"), "1".into());
//!         map.insert(Cow::Owned(format!("{}-param", "multi-word")), "2".into());
//!         map
//!     };
//!
//!     assert_eq!("text one 1 second 2", LOCALES.lookup_with_args(&US_ENGLISH, "parameter2", &args));
//!     assert_eq!("texte une 1 seconde 2", LOCALES.lookup_with_args(&FRENCH, "parameter2", &args));
//!
//!     assert_eq!("text one 1 second 2", LOCALES.try_lookup_with_args(&US_ENGLISH, "parameter2", &args).unwrap());
//!     assert_eq!("texte une 1 seconde 2", LOCALES.try_lookup_with_args(&FRENCH, "parameter2", &args).unwrap());
//! }
//! ```
//!
//! ### Tera
//! With the `tera` feature you can use `FluentLoader` as a Tera function.
//! It accepts a `key` parameter pointing to a fluent resource and `lang` for
//! what language to get that key for. Optionally you can pass extra arguments
//! to the function as arguments to the resource. `fluent-templates` will
//! automatically convert argument keys from Tera's `snake_case` to the fluent's
//! preferred `kebab-case` arguments.
//! The `lang` parameter is optional when the default language of the corresponding
//! `FluentLoader` is set (see [`FluentLoader::with_default_lang`]).
//!
//! ```toml
//!fluent-templates = { version = "*", features = ["tera"] }
//!```
//!
//! ```rust
//! use fluent_templates::{FluentLoader, static_loader};
//!
//! static_loader! {
//!     static LOCALES = {
//!         locales: "./tests/locales",
//!         fallback_language: "en-US",
//!         // Removes unicode isolating marks around arguments, you typically
//!         // should only set to false when testing.
//!         customise: |bundle| bundle.set_use_isolating(false),
//!     };
//! }
//!
//! fn main() {
//! #   #[cfg(feature = "tera")] {
//!         let mut tera = tera::Tera::default();
//!         let ctx = tera::Context::default();
//!         tera.register_function("fluent", FluentLoader::new(&*LOCALES));
//!         assert_eq!(
//!             "Hello World!",
//!             tera.render_str(r#"{{ fluent(key="hello-world", lang="en-US") }}"#, &ctx).unwrap()
//!         );
//!         assert_eq!(
//!             "Hello Alice!",
//!             tera.render_str(r#"{{ fluent(key="greeting", lang="en-US", name="Alice") }}"#, &ctx).unwrap()
//!         );
//!     }
//! # }
//! ```
//!
//! ### Handlebars
//! In handlebars, `fluent-templates` will read the `lang` field in your
//! [`handlebars::Context`] while rendering.
//!
//! ```toml
//!fluent-templates = { version = "*", features = ["handlebars"] }
//!```
//!
//! ```rust
//! use fluent_templates::{FluentLoader, static_loader};
//!
//! static_loader! {
//!     static LOCALES = {
//!         locales: "./tests/locales",
//!         fallback_language: "en-US",
//!         // Removes unicode isolating marks around arguments, you typically
//!         // should only set to false when testing.
//!         customise: |bundle| bundle.set_use_isolating(false),
//!     };
//! }
//!
//! fn main() {
//! # #[cfg(feature = "handlebars")] {
//!     let mut handlebars = handlebars::Handlebars::new();
//!     handlebars.register_helper("fluent", Box::new(FluentLoader::new(&*LOCALES)));
//!     let data = serde_json::json!({"lang": "zh-CN"});
//!     assert_eq!("Hello World!", handlebars.render_template(r#"{{fluent "hello-world"}}"#, &data).unwrap());
//!     assert_eq!("Hello Alice!", handlebars.render_template(r#"{{fluent "greeting" name="Alice"}}"#, &data).unwrap());
//! # }
//! }
//! ```
//!
//! ### Handlebars helper syntax.
//! The main helper provided is the `{{fluent}}` helper. If you have the
//! following Fluent file:
//!
//! ```fluent
//! foo-bar = "foo bar"
//! placeholder = this has a placeholder { $variable }
//! placeholder2 = this has { $variable1 } { $variable2 }
//! ```
//!
//! You can include the strings in your template with
//!
//! ```hbs
//! <!-- will render "foo bar" -->
//! {{fluent "foo-bar"}}
//! <!-- will render "this has a placeholder baz" -->
//! {{fluent "placeholder" variable="baz"}}
//!```
//!
//! You may also use the `{{fluentparam}}` helper to specify [variables],
//! especially if you need them to be multiline.
//!
//! ```hbs
//! {{#fluent "placeholder2"}}
//!     {{#fluentparam "variable1"}}
//!         first line
//!         second line
//!     {{/fluentparam}}
//!     {{#fluentparam "variable2"}}
//!         first line
//!         second line
//!     {{/fluentparam}}
//! {{/fluent}}
//! ```
//!
//!
//! [variables]: https://projectfluent.org/fluent/guide/variables.html
//! [`static_loader!`]: ./macro.static_loader.html
//! [`StaticLoader`]: ./struct.StaticLoader.html
//! [`ArcLoader`]: ./struct.ArcLoader.html
//! [`FluentLoader::with_default_lang`]: ./struct.FluentLoader.html#method.with_default_lang
//! [`handlebars::Context`]: https://docs.rs/handlebars/3.1.0/handlebars/struct.Context.html
#![warn(missing_docs)]

#[doc(hidden)]
pub extern crate fluent_bundle;

#[doc(hidden)]
pub type FluentBundle<R> =
    fluent_bundle::bundle::FluentBundle<R, intl_memoizer::concurrent::IntlLangMemoizer>;

pub use error::LoaderError;
pub use loader::{ArcLoader, ArcLoaderBuilder, FluentLoader, Loader, MultiLoader, StaticLoader};

mod error;
#[doc(hidden)]
pub mod fs;
mod languages;
#[doc(hidden)]
pub mod loader;

#[cfg(feature = "macros")]
pub use fluent_template_macros::static_loader;
#[cfg(feature = "macros")]
pub use unic_langid::langid;
pub use unic_langid::LanguageIdentifier;

/// A convenience `Result` type that defaults to `error::Loader`.
pub type Result<T, E = error::LoaderError> = std::result::Result<T, E>;

#[cfg(test)]
mod tests {
    use super::*;
    use crate::Loader;
    use unic_langid::{langid, LanguageIdentifier};

    #[test]
    fn check_if_loader_is_object_safe() {
        const US_ENGLISH: LanguageIdentifier = langid!("en-US");

        let loader = ArcLoader::builder("./tests/locales", US_ENGLISH)
            .customize(|bundle| bundle.set_use_isolating(false))
            .build()
            .unwrap();

        let loader: Box<dyn Loader> = Box::new(loader);
        assert_eq!("Hello World!", loader.lookup(&US_ENGLISH, "hello-world"));
    }
}