1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60 61 62 63 64 65 66 67 68 69 70 71 72 73 74 75 76 77 78 79 80 81 82 83 84 85 86 87 88 89 90 91 92 93 94 95 96 97 98 99 100 101 102 103 104 105 106 107 108 109 110 111 112 113 114 115 116 117 118 119 120 121 122 123 124 125 126 127 128 129 130 131 132 133 134 135 136 137 138 139 140 141 142 143 144 145 146 147 148 149 150 151 152 153 154 155 156 157 158 159 160 161 162 163 164 165 166 167 168 169 170 171 172 173 174 175 176 177 178 179 180 181 182 183 184 185 186 187 188 189 190 191 192 193 194 195 196 197 198 199 200 201 202 203 204 205 206 207 208 209 210 211 212 213 214 215 216 217 218 219 220 221 222 223 224 225 226 227 228 229 230 231 232 233 234 235 236 237 238 239 240 241 242 243 244 245 246 247 248 249 250 251 252 253 254 255 256 257 258 259 260 261 262 263 264
// This file is part of ICU4X. For terms of use, please see the file
// called LICENSE at the top level of the ICU4X source tree
// (online at: https://github.com/unicode-org/icu4x/blob/main/LICENSE ).
//! Tools for locale fallback, enabling arbitrary input locales to be mapped into the nearest
//! locale with data.
use crate::provider::*;
use icu_locale_core::subtags::*;
use icu_provider::prelude::*;
#[doc(inline)]
pub use icu_provider::fallback::{LocaleFallbackConfig, LocaleFallbackPriority};
mod algorithms;
/// Implements the algorithm defined in *[UTS #35: Locale Inheritance and Matching]*.
///
/// Note that this implementation performs some additional steps compared to the *UTS #35*
/// algorithm. See *[the design doc]* for a detailed description and [#2243](
/// https://github.com/unicode-org/icu4x/issues/2243) to track alignment with *UTS #35*.
///
/// If running fallback in a loop, use [`DataLocale::is_default()`] to break from the loop.
///
/// # Examples
///
/// ```
/// use icu::locale::fallback::LocaleFallbacker;
/// use icu::locale::locale;
///
/// // Set up a LocaleFallbacker with data.
/// let fallbacker = LocaleFallbacker::new();
///
/// // Create a LocaleFallbackerIterator with a default configuration.
/// // By default, uses language priority.
/// let mut fallback_iterator = fallbacker
/// .for_config(Default::default())
/// .fallback_for(locale!("hi-Latn-IN").into());
///
/// // Run the algorithm and check the results.
/// assert_eq!(fallback_iterator.get(), &locale!("hi-Latn-IN").into());
/// fallback_iterator.step();
/// assert_eq!(fallback_iterator.get(), &locale!("hi-Latn").into());
/// fallback_iterator.step();
/// assert_eq!(fallback_iterator.get(), &locale!("en-IN").into());
/// fallback_iterator.step();
/// assert_eq!(fallback_iterator.get(), &locale!("en-001").into());
/// fallback_iterator.step();
/// assert_eq!(fallback_iterator.get(), &locale!("en").into());
/// fallback_iterator.step();
/// assert_eq!(fallback_iterator.get(), &locale!("und").into());
/// ```
///
/// [UTS #35: Locale Inheritance and Matching]: https://www.unicode.org/reports/tr35/#Locale_Inheritance
/// [the design doc]: https://docs.google.com/document/d/1Mp7EUyl-sFh_HZYgyeVwj88vJGpCBIWxzlCwGgLCDwM/edit
/// [language identifier]: icu::locale::LanguageIdentifier
#[doc(hidden)] // canonical location in super
#[derive(Debug, Clone, PartialEq)]
pub struct LocaleFallbacker {
likely_subtags: DataPayload<LikelySubtagsForLanguageV1Marker>,
parents: DataPayload<ParentsV1Marker>,
}
/// Borrowed version of [`LocaleFallbacker`].
#[derive(Debug, Clone, Copy, PartialEq)]
pub struct LocaleFallbackerBorrowed<'a> {
likely_subtags: &'a LikelySubtagsForLanguageV1<'a>,
parents: &'a ParentsV1<'a>,
}
/// A [`LocaleFallbackerBorrowed`] with an associated [`LocaleFallbackConfig`].
#[derive(Debug, Clone, Copy, PartialEq)]
pub struct LocaleFallbackerWithConfig<'a> {
likely_subtags: &'a LikelySubtagsForLanguageV1<'a>,
parents: &'a ParentsV1<'a>,
config: LocaleFallbackConfig,
}
/// Inner iteration type. Does not own the item under fallback.
#[derive(Debug)]
struct LocaleFallbackIteratorInner<'a> {
likely_subtags: &'a LikelySubtagsForLanguageV1<'a>,
parents: &'a ParentsV1<'a>,
config: LocaleFallbackConfig,
backup_subdivision: Option<Subtag>,
backup_variant: Option<Variant>,
backup_region: Option<Region>,
max_script: Option<Script>,
}
/// Iteration type for locale fallback operations.
///
/// Because the `Iterator` trait does not allow items to borrow from the iterator, this class does
/// not implement that trait. Instead, use `.step()` and `.get()`.
#[derive(Debug)]
pub struct LocaleFallbackIterator<'a, 'b> {
current: DataLocale,
inner: LocaleFallbackIteratorInner<'a>,
phantom: core::marker::PhantomData<&'b ()>,
}
impl LocaleFallbacker {
/// Creates a [`LocaleFallbacker`] with compiled fallback data (likely subtags and parent locales).
///
/// ✨ *Enabled with the `compiled_data` Cargo feature.*
///
/// [📚 Help choosing a constructor](icu_provider::constructors)
#[cfg(feature = "compiled_data")]
#[allow(clippy::new_ret_no_self)] // keeping constructors together
pub const fn new<'a>() -> LocaleFallbackerBorrowed<'a> {
// Safety: we're transmuting down from LocaleFallbackerBorrowed<'static> to LocaleFallbackerBorrowed<'a>
// ZeroMaps use associated types in a way that confuse the compiler which gives up and marks them
// as invariant. However, they are covariant, and in non-const code this covariance can be safely triggered
// using Yokeable::transform. In const code we must transmute. In the long run we should
// be able to `transform()` in const code, and also we will have hopefully improved map polymorphism (#3128)
unsafe { core::mem::transmute(LocaleFallbackerBorrowed::<'static>::new()) }
}
icu_provider::gen_any_buffer_data_constructors!(() -> error: DataError,
functions: [
new: skip,
try_new_with_any_provider,
try_new_with_buffer_provider,
try_new_unstable,
Self
]);
#[doc = icu_provider::gen_any_buffer_unstable_docs!(UNSTABLE, Self::new)]
pub fn try_new_unstable<P>(provider: &P) -> Result<Self, DataError>
where
P: DataProvider<LikelySubtagsForLanguageV1Marker> + DataProvider<ParentsV1Marker> + ?Sized,
{
let likely_subtags = provider.load(Default::default())?.payload;
let parents = provider.load(Default::default())?.payload;
Ok(LocaleFallbacker {
likely_subtags,
parents,
})
}
/// Creates a [`LocaleFallbacker`] without fallback data. Using this constructor may result in
/// surprising behavior, especially in multi-script languages.
pub fn new_without_data() -> Self {
LocaleFallbacker {
likely_subtags: DataPayload::from_owned(LikelySubtagsForLanguageV1 {
language: Default::default(),
language_region: Default::default(),
language_script: Default::default(),
// Unused
und: (
Default::default(),
crate::subtags::script!("Zzzz"),
crate::subtags::region!("ZZ"),
),
}),
parents: DataPayload::from_owned(Default::default()),
}
}
/// Associates a configuration with this fallbacker.
#[inline]
pub fn for_config(&self, config: LocaleFallbackConfig) -> LocaleFallbackerWithConfig {
self.as_borrowed().for_config(config)
}
/// Creates a borrowed version of this fallbacker for performance.
pub fn as_borrowed(&self) -> LocaleFallbackerBorrowed {
LocaleFallbackerBorrowed {
likely_subtags: self.likely_subtags.get(),
parents: self.parents.get(),
}
}
}
impl<'a> LocaleFallbackerBorrowed<'a> {
/// Associates a configuration with this fallbacker.
#[inline]
pub const fn for_config(self, config: LocaleFallbackConfig) -> LocaleFallbackerWithConfig<'a> {
LocaleFallbackerWithConfig {
likely_subtags: self.likely_subtags,
parents: self.parents,
config,
}
}
}
#[cfg(feature = "compiled_data")]
impl Default for LocaleFallbackerBorrowed<'static> {
fn default() -> Self {
Self::new()
}
}
impl LocaleFallbackerBorrowed<'static> {
/// Creates a [`LocaleFallbackerBorrowed`] with compiled fallback data (likely subtags and parent locales).
///
/// ✨ *Enabled with the `compiled_data` Cargo feature.*
///
/// [📚 Help choosing a constructor](icu_provider::constructors)
#[cfg(feature = "compiled_data")]
pub const fn new() -> Self {
Self {
likely_subtags: crate::provider::Baked::SINGLETON_LIKELY_SUBTAGS_FOR_LANGUAGE_V1_MARKER,
parents: crate::provider::Baked::SINGLETON_PARENTS_V1_MARKER,
}
}
/// Cheaply converts a [`LocaleFallbackerBorrowed<'static>`] into a [`LocaleFallbacker`].
///
/// Note: Due to branching and indirection, using [`LocaleFallbacker`] might inhibit some
/// compile-time optimizations that are possible with [`LocaleFallbackerBorrowed`].
pub const fn static_to_owned(self) -> LocaleFallbacker {
LocaleFallbacker {
likely_subtags: DataPayload::from_static_ref(self.likely_subtags),
parents: DataPayload::from_static_ref(self.parents),
}
}
}
impl<'a> LocaleFallbackerWithConfig<'a> {
/// Creates an iterator based on a [`DataLocale`].
///
/// If you have a [`Locale`](icu_locale_core::Locale), call `.into()` to get a [`DataLocale`].
///
/// When first initialized, the locale is normalized according to the fallback algorithm.
pub fn fallback_for(&self, mut locale: DataLocale) -> LocaleFallbackIterator<'a, 'static> {
let mut default_script = None;
self.normalize(&mut locale, &mut default_script);
let max_script = locale.script.or(default_script);
LocaleFallbackIterator {
current: locale,
inner: LocaleFallbackIteratorInner {
likely_subtags: self.likely_subtags,
parents: self.parents,
config: self.config,
backup_subdivision: None,
backup_variant: None,
backup_region: None,
max_script,
},
phantom: core::marker::PhantomData,
}
}
}
impl LocaleFallbackIterator<'_, '_> {
/// Borrows the current [`DataLocale`] under fallback.
pub fn get(&self) -> &DataLocale {
&self.current
}
/// Takes the current [`DataLocale`] under fallback.
pub fn take(self) -> DataLocale {
self.current
}
/// Performs one step of the locale fallback algorithm.
///
/// The fallback is completed once the inner [`DataLocale`] becomes [`DataLocale::default()`].
pub fn step(&mut self) -> &mut Self {
self.inner.step(&mut self.current);
self
}
}