| // 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 ). |
| |
| //! Options to define fallback behaviour. |
| //! |
| //! These options are consumed by the `LocaleFallbacker` in the `icu_locid_transforms` crate |
| //! (or the `icu::locid_transforms` module), but are defined here because they are used by `DataKey`. |
| |
| use icu_locid::extensions::unicode::Key; |
| |
| /// Hint for which subtag to prioritize during fallback. |
| /// |
| /// For example, `"en-US"` might fall back to either `"en"` or `"und-US"` depending |
| /// on this enum. |
| #[derive(Debug, PartialEq, Eq, Copy, Clone, PartialOrd, Ord)] |
| #[non_exhaustive] |
| pub enum LocaleFallbackPriority { |
| /// Prioritize the language. This is the default behavior. |
| /// |
| /// For example, `"en-US"` should go to `"en"` and then `"und"`. |
| Language, |
| /// Prioritize the region. |
| /// |
| /// For example, `"en-US"` should go to `"und-US"` and then `"und"`. |
| Region, |
| /// Collation-specific fallback rules. Similar to language priority. |
| /// |
| /// For example, `"zh-Hant"` goes to `"zh"` before `"und"`. |
| Collation, |
| } |
| |
| impl LocaleFallbackPriority { |
| /// Const-friendly version of [`Default::default`]. |
| pub const fn const_default() -> Self { |
| Self::Language |
| } |
| } |
| |
| impl Default for LocaleFallbackPriority { |
| fn default() -> Self { |
| Self::const_default() |
| } |
| } |
| |
| /// What additional data is required to load when performing fallback. |
| #[derive(Debug, PartialEq, Eq, Copy, Clone, PartialOrd, Ord)] |
| #[non_exhaustive] |
| pub enum LocaleFallbackSupplement { |
| /// Collation supplement |
| Collation, |
| } |
| |
| /// Configuration settings for a particular fallback operation. |
| #[derive(Debug, Clone, PartialEq, Eq, Copy)] |
| #[non_exhaustive] |
| pub struct LocaleFallbackConfig { |
| /// Strategy for choosing which subtags to drop during locale fallback. |
| /// |
| /// # Examples |
| /// |
| /// Retain the language and script subtags until the final step: |
| /// |
| /// ``` |
| /// use icu_locid::locale; |
| /// use icu_locid_transform::fallback::LocaleFallbackConfig; |
| /// use icu_locid_transform::fallback::LocaleFallbackPriority; |
| /// use icu_locid_transform::LocaleFallbacker; |
| /// |
| /// // Set up the fallback iterator. |
| /// let fallbacker = LocaleFallbacker::new(); |
| /// let mut config = LocaleFallbackConfig::default(); |
| /// config.priority = LocaleFallbackPriority::Language; |
| /// let mut fallback_iterator = fallbacker |
| /// .for_config(config) |
| /// .fallback_for(locale!("ca-ES-valencia").into()); |
| /// |
| /// // Run the algorithm and check the results. |
| /// assert_eq!(fallback_iterator.get(), &locale!("ca-ES-valencia").into()); |
| /// fallback_iterator.step(); |
| /// assert_eq!(fallback_iterator.get(), &locale!("ca-ES").into()); |
| /// fallback_iterator.step(); |
| /// assert_eq!(fallback_iterator.get(), &locale!("ca-valencia").into()); |
| /// fallback_iterator.step(); |
| /// assert_eq!(fallback_iterator.get(), &locale!("ca").into()); |
| /// fallback_iterator.step(); |
| /// assert_eq!(fallback_iterator.get(), &locale!("und").into()); |
| /// ``` |
| /// |
| /// Retain the region subtag until the final step: |
| /// |
| /// ``` |
| /// use icu_locid::locale; |
| /// use icu_locid_transform::fallback::LocaleFallbackConfig; |
| /// use icu_locid_transform::fallback::LocaleFallbackPriority; |
| /// use icu_locid_transform::LocaleFallbacker; |
| /// |
| /// // Set up the fallback iterator. |
| /// let fallbacker = LocaleFallbacker::new(); |
| /// let mut config = LocaleFallbackConfig::default(); |
| /// config.priority = LocaleFallbackPriority::Region; |
| /// let mut fallback_iterator = fallbacker |
| /// .for_config(config) |
| /// .fallback_for(locale!("ca-ES-valencia").into()); |
| /// |
| /// // Run the algorithm and check the results. |
| /// assert_eq!(fallback_iterator.get(), &locale!("ca-ES-valencia").into()); |
| /// fallback_iterator.step(); |
| /// assert_eq!(fallback_iterator.get(), &locale!("ca-ES").into()); |
| /// fallback_iterator.step(); |
| /// assert_eq!(fallback_iterator.get(), &locale!("und-ES-valencia").into()); |
| /// fallback_iterator.step(); |
| /// assert_eq!(fallback_iterator.get(), &locale!("und-ES").into()); |
| /// fallback_iterator.step(); |
| /// assert_eq!(fallback_iterator.get(), &locale!("und").into()); |
| /// ``` |
| pub priority: LocaleFallbackPriority, |
| /// An extension keyword to retain during locale fallback. |
| /// |
| /// # Examples |
| /// |
| /// ``` |
| /// use icu_locid::locale; |
| /// use icu_locid_transform::fallback::LocaleFallbackConfig; |
| /// use icu_locid_transform::LocaleFallbacker; |
| /// |
| /// // Set up the fallback iterator. |
| /// let fallbacker = LocaleFallbacker::new(); |
| /// let mut config = LocaleFallbackConfig::default(); |
| /// config.extension_key = Some(icu_locid::extensions::unicode::key!("nu")); |
| /// let mut fallback_iterator = fallbacker |
| /// .for_config(config) |
| /// .fallback_for(locale!("ar-EG-u-nu-latn").into()); |
| /// |
| /// // Run the algorithm and check the results. |
| /// assert_eq!(fallback_iterator.get(), &locale!("ar-EG-u-nu-latn").into()); |
| /// fallback_iterator.step(); |
| /// assert_eq!(fallback_iterator.get(), &locale!("ar-EG").into()); |
| /// fallback_iterator.step(); |
| /// assert_eq!(fallback_iterator.get(), &locale!("ar-u-nu-latn").into()); |
| /// fallback_iterator.step(); |
| /// assert_eq!(fallback_iterator.get(), &locale!("ar").into()); |
| /// fallback_iterator.step(); |
| /// assert_eq!(fallback_iterator.get(), &locale!("und").into()); |
| /// ``` |
| pub extension_key: Option<Key>, |
| /// Fallback supplement data key to customize fallback rules. |
| /// |
| /// For example, most data keys for collation add additional parent locales, such as |
| /// "yue" to "zh-Hant", and data used for the `"-u-co"` extension keyword fallback. |
| /// |
| /// Currently the only supported fallback supplement is `LocaleFallbackSupplement::Collation`, but more may be |
| /// added in the future. |
| /// |
| /// # Examples |
| /// |
| /// ``` |
| /// use icu_locid::locale; |
| /// use icu_locid_transform::fallback::LocaleFallbackConfig; |
| /// use icu_locid_transform::fallback::LocaleFallbackPriority; |
| /// use icu_locid_transform::fallback::LocaleFallbackSupplement; |
| /// use icu_locid_transform::LocaleFallbacker; |
| /// |
| /// // Set up the fallback iterator. |
| /// let fallbacker = LocaleFallbacker::new(); |
| /// let mut config = LocaleFallbackConfig::default(); |
| /// config.priority = LocaleFallbackPriority::Collation; |
| /// config.fallback_supplement = Some(LocaleFallbackSupplement::Collation); |
| /// let mut fallback_iterator = fallbacker |
| /// .for_config(config) |
| /// .fallback_for(locale!("yue-HK").into()); |
| /// |
| /// // Run the algorithm and check the results. |
| /// // TODO(#1964): add "zh" as a target. |
| /// assert_eq!(fallback_iterator.get(), &locale!("yue-HK").into()); |
| /// fallback_iterator.step(); |
| /// assert_eq!(fallback_iterator.get(), &locale!("yue").into()); |
| /// fallback_iterator.step(); |
| /// assert_eq!(fallback_iterator.get(), &locale!("zh-Hant").into()); |
| /// fallback_iterator.step(); |
| /// assert_eq!(fallback_iterator.get(), &locale!("und").into()); |
| /// ``` |
| pub fallback_supplement: Option<LocaleFallbackSupplement>, |
| } |
| |
| impl LocaleFallbackConfig { |
| /// Const version of [`Default::default`]. |
| pub const fn const_default() -> Self { |
| Self { |
| priority: LocaleFallbackPriority::const_default(), |
| extension_key: None, |
| fallback_supplement: None, |
| } |
| } |
| } |
| |
| impl Default for LocaleFallbackConfig { |
| fn default() -> Self { |
| Self::const_default() |
| } |
| } |