wip

provider/baked/src/binary_search.rs

@@ -86,6 +86,10 @@ impl<K: BinarySearchKey, M: DataMarker> super::DataStore<M> for Data<K, M> {
     fn iter(&self) -> Self::IterReturn {
         self.0.iter().map(|&(k, _)| K::to_id(k))
     }
+
+    fn contains(&self, id: DataIdentifierBorrowed) -> bool {
+        self.0.binary_search_by(|&(k, _)| K::cmp(k, id)).is_ok()
+    }
 }
 
 pub trait BinarySearchKey: 'static {

provider/baked/src/export.rs

@@ -568,6 +568,15 @@ impl DataExporter for BakedExporter {
                             })
                         }
                     }
+
+                    impl icu_provider::CanLoad<#marker_bake> for $provider {
+                        fn can_load(
+                            &self,
+                            req: icu_provider::DataRequest,
+                        ) -> Result<bool, icu_provider::DataError> {
+                            Ok(icu_provider_baked::DataStore::contains(&Self::#data_ident, req.id))
+                        }
+                    }
                 },
                 quote! {
                     #maybe_msrv

provider/baked/src/lib.rs

@@ -20,4 +20,6 @@ pub trait DataStore<M: DataMarker> {
 
     type IterReturn: Iterator<Item = DataIdentifierCow<'static>>;
     fn iter(&self) -> Self::IterReturn;
+
+    fn contains(&self, id: DataIdentifierBorrowed) -> bool;
 }

provider/baked/tests/data/hello_world_v1_marker.rs.data

@@ -50,6 +50,11 @@ macro_rules! __impl_hello_world_v1_marker {
                 Ok(icu_provider::DataResponse { payload: icu_provider::DataPayload::from_static_ref(payload), metadata })
             }
         }
+        impl icu_provider::CanLoad<icu_provider::hello_world::HelloWorldV1Marker> for $provider {
+            fn can_load(&self, req: icu_provider::DataRequest) -> Result<bool, icu_provider::DataError> {
+                Ok(icu_provider_baked::DataStore::contains(&Self::DATA_HELLO_WORLD_V1_MARKER, req.id))
+            }
+        }
     };
     ($ provider : ty , ITER) => {
         __impl_hello_world_v1_marker!($provider);

provider/core/src/data_provider.rs

@@ -74,6 +74,12 @@ where
     }
 }
 
+/// TODO
+pub trait CanLoad<M: DataMarker>: DataProvider<M> {
+    /// TODO
+    fn can_load(&self, req: DataRequest) -> Result<bool, DataError>;
+}
+
 /// A data provider that loads data for a specific data type.
 ///
 /// Unlike [`DataProvider`], there may be multiple markers corresponding to the same data type.

provider/core/src/lib.rs

@@ -132,7 +132,7 @@ pub mod serde_borrow_de_utils;
 
 mod data_provider;
 pub use data_provider::{
-    BoundDataProvider, DataProvider, DataProviderWithMarker, DynamicDataProvider,
+    BoundDataProvider, CanLoad, DataProvider, DataProviderWithMarker, DynamicDataProvider,
 };
 #[cfg(feature = "std")]
 pub use data_provider::{IterableDataProvider, IterableDynamicDataProvider};