Adding upstream version 124.0.1.upstream/124.0.1

Signed-off-by: Daniel Baumann <daniel.baumann@progress-linux.org>

1 files changed, 201 insertions, 0 deletions

diff --git a/third_party/rust/icu_provider/src/fallback.rs b/third_party/rust/icu_provider/src/fallback.rs
new file mode 100644
index 0000000000..5c4e13b8da
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+++ b/third_party/rust/icu_provider/src/fallback.rs
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+// 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()
+    }
+}