1 files changed, 112 insertions, 0 deletions
diff --git a/third_party/rust/icu_provider_adapters/src/empty.rs b/third_party/rust/icu_provider_adapters/src/empty.rs
new file mode 100644
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+++ b/third_party/rust/icu_provider_adapters/src/empty.rs
@@ -0,0 +1,112 @@
+// 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 ).
+
+//! Empty data provider implementations.
+//!
+//! Use [`EmptyDataProvider`] as a stand-in for a provider that always fails.
+
+use icu_provider::prelude::*;
+
+/// A data provider that always returns an error.
+///
+/// The returned error kind is configurable.
+///
+/// # Examples
+///
+/// ```
+/// use icu_provider::hello_world::HelloWorldV1Marker;
+/// use icu_provider::prelude::*;
+/// use icu_provider_adapters::empty::EmptyDataProvider;
+///
+/// let provider = EmptyDataProvider::new();
+///
+/// assert!(matches!(
+///     provider.load_any(HelloWorldV1Marker::KEY, Default::default()),
+///     Err(DataError {
+///         kind: DataErrorKind::MissingDataKey,
+///         ..
+///     })
+/// ));
+/// ```
+#[derive(Debug)]
+pub struct EmptyDataProvider {
+    error_kind: DataErrorKind,
+}
+
+impl Default for EmptyDataProvider {
+    fn default() -> Self {
+        Self::new()
+    }
+}
+
+impl EmptyDataProvider {
+    /// Creates a data provider that always returns [`DataErrorKind::MissingDataKey`].
+    pub fn new() -> Self {
+        Self {
+            error_kind: DataErrorKind::MissingDataKey,
+        }
+    }
+
+    /// Creates a data provider that always returns the specified error kind.
+    pub fn new_with_error_kind(error_kind: DataErrorKind) -> Self {
+        Self { error_kind }
+    }
+}
+
+impl AnyProvider for EmptyDataProvider {
+    fn load_any(&self, key: DataKey, base_req: DataRequest) -> Result<AnyResponse, DataError> {
+        Err(self.error_kind.with_req(key, base_req))
+    }
+}
+
+impl BufferProvider for EmptyDataProvider {
+    fn load_buffer(
+        &self,
+        key: DataKey,
+        base_req: DataRequest,
+    ) -> Result<DataResponse<BufferMarker>, DataError> {
+        Err(self.error_kind.with_req(key, base_req))
+    }
+}
+
+impl<M> DynamicDataProvider<M> for EmptyDataProvider
+where
+    M: DataMarker,
+{
+    fn load_data(&self, key: DataKey, base_req: DataRequest) -> Result<DataResponse<M>, DataError> {
+        Err(self.error_kind.with_req(key, base_req))
+    }
+}
+
+impl<M> DataProvider<M> for EmptyDataProvider
+where
+    M: KeyedDataMarker,
+{
+    fn load(&self, base_req: DataRequest) -> Result<DataResponse<M>, DataError> {
+        Err(self.error_kind.with_req(M::KEY, base_req))
+    }
+}
+
+#[cfg(feature = "datagen")]
+impl<M> icu_provider::datagen::IterableDataProvider<M> for EmptyDataProvider
+where
+    M: KeyedDataMarker,
+{
+    fn supported_locales(&self) -> Result<alloc::vec::Vec<DataLocale>, DataError> {
+        Ok(vec![])
+    }
+}
+
+#[cfg(feature = "datagen")]
+impl<M> icu_provider::datagen::IterableDynamicDataProvider<M> for EmptyDataProvider
+where
+    M: DataMarker,
+{
+    fn supported_locales_for_key(
+        &self,
+        _: DataKey,
+    ) -> Result<alloc::vec::Vec<DataLocale>, DataError> {
+        Ok(vec![])
+    }
+}