crates/icu_provider/src/data_provider.rs - platform/external/rust/android-crates-io - Git at Google

 // 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 ).

 use alloc::{boxed::Box, collections::BTreeSet};
 use core::marker::PhantomData;
 use yoke::Yokeable;

 use crate::prelude::*;

 /// A data provider that loads data for a specific [`DataMarkerInfo`].
 pub trait DataProvider<M>
 where
     M: DataMarker,
 {
     /// Query the provider for data, returning the result.
     ///
     /// Returns [`Ok`] if the request successfully loaded data. If data failed to load, returns an
     /// Error with more information.
     fn load(&self, req: DataRequest) -> Result<DataResponse<M>, DataError>;
 }

 impl<M, P> DataProvider<M> for &P
 where
     M: DataMarker,
     P: DataProvider<M> + ?Sized,
 {
     #[inline]
     fn load(&self, req: DataRequest) -> Result<DataResponse<M>, DataError> {
         (*self).load(req)
     }
 }

 impl<M, P> DataProvider<M> for Box<P>
 where
     M: DataMarker,
     P: DataProvider<M> + ?Sized,
 {
     #[inline]
     fn load(&self, req: DataRequest) -> Result<DataResponse<M>, DataError> {
         (**self).load(req)
     }
 }

 impl<M, P> DataProvider<M> for alloc::rc::Rc<P>
 where
     M: DataMarker,
     P: DataProvider<M> + ?Sized,
 {
     #[inline]
     fn load(&self, req: DataRequest) -> Result<DataResponse<M>, DataError> {
         (**self).load(req)
     }
 }

 /// A [`DataProvider`] that can iterate over all supported [`DataIdentifierCow`]s.
 ///
 /// The provider is not allowed to return `Ok` for requests that were not returned by `iter_ids`,
 /// and must not fail with a [`DataErrorKind::IdentifierNotFound`] for requests that were returned.
 pub trait IterableDataProvider<M: DataMarker>: DataProvider<M> {
     /// Returns a set of [`DataIdentifierCow`].
     fn iter_ids(&self) -> Result<BTreeSet<DataIdentifierCow>, DataError>;
 }

 #[cfg(target_has_atomic = "ptr")]
 impl<M, P> DataProvider<M> for alloc::sync::Arc<P>
 where
     M: DataMarker,
     P: DataProvider<M> + ?Sized,
 {
     #[inline]
     fn load(&self, req: DataRequest) -> Result<DataResponse<M>, DataError> {
         (**self).load(req)
     }
 }

 /// A data provider that can determine whether it can load a particular data identifier,
 /// potentially cheaper than actually performing the load.
 pub trait DryDataProvider<M: DataMarker>: DataProvider<M> {
     /// This method goes through the motions of [`load`], but only returns the metadata.
     ///
     /// If `dry_load` returns an error, [`load`] must return the same error, but
     /// not vice-versa. Concretely, [`load`] could return deserialization or I/O errors
     /// that `dry_load` cannot predict.
     ///
     /// [`load`]: DataProvider::load
     fn dry_load(&self, req: DataRequest) -> Result<DataResponseMetadata, 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.
 /// This is often the case when returning `dyn` trait objects such as [`AnyMarker`].
 ///
 /// [`AnyMarker`]: crate::any::AnyMarker
 pub trait DynamicDataProvider<M>
 where
     M: DynamicDataMarker,
 {
     /// Query the provider for data, returning the result.
     ///
     /// Returns [`Ok`] if the request successfully loaded data. If data failed to load, returns an
     /// Error with more information.
     fn load_data(
         &self,
         marker: DataMarkerInfo,
         req: DataRequest,
     ) -> Result<DataResponse<M>, DataError>;
 }

 /// A dynanmic data provider that can determine whether it can load a particular data identifier,
 /// potentially cheaper than actually performing the load.
 pub trait DynamicDryDataProvider<M: DynamicDataMarker>: DynamicDataProvider<M> {
     /// This method goes through the motions of [`load_data`], but only returns the metadata.
     ///
     /// If `dry_load_data` returns an error, [`load_data`] must return the same error, but
     /// not vice-versa. Concretely, [`load_data`] could return deserialization or I/O errors
     /// that `dry_load_data` cannot predict.
     ///
     /// [`load_data`]: DynamicDataProvider::load_data
     fn dry_load_data(
         &self,
         marker: DataMarkerInfo,
         req: DataRequest,
     ) -> Result<DataResponseMetadata, DataError>;
 }

 impl<M, P> DynamicDataProvider<M> for &P
 where
     M: DynamicDataMarker,
     P: DynamicDataProvider<M> + ?Sized,
 {
     #[inline]
     fn load_data(
         &self,
         marker: DataMarkerInfo,
         req: DataRequest,
     ) -> Result<DataResponse<M>, DataError> {
         (*self).load_data(marker, req)
     }
 }

 impl<M, P> DynamicDataProvider<M> for Box<P>
 where
     M: DynamicDataMarker,
     P: DynamicDataProvider<M> + ?Sized,
 {
     #[inline]
     fn load_data(
         &self,
         marker: DataMarkerInfo,
         req: DataRequest,
     ) -> Result<DataResponse<M>, DataError> {
         (**self).load_data(marker, req)
     }
 }

 impl<M, P> DynamicDataProvider<M> for alloc::rc::Rc<P>
 where
     M: DynamicDataMarker,
     P: DynamicDataProvider<M> + ?Sized,
 {
     #[inline]
     fn load_data(
         &self,
         marker: DataMarkerInfo,
         req: DataRequest,
     ) -> Result<DataResponse<M>, DataError> {
         (**self).load_data(marker, req)
     }
 }

 #[cfg(target_has_atomic = "ptr")]
 impl<M, P> DynamicDataProvider<M> for alloc::sync::Arc<P>
 where
     M: DynamicDataMarker,
     P: DynamicDataProvider<M> + ?Sized,
 {
     #[inline]
     fn load_data(
         &self,
         marker: DataMarkerInfo,
         req: DataRequest,
     ) -> Result<DataResponse<M>, DataError> {
         (**self).load_data(marker, req)
     }
 }

 /// A [`DynamicDataProvider`] that can iterate over all supported [`DataIdentifierCow`]s for a certain marker.
 ///
 /// The provider is not allowed to return `Ok` for requests that were not returned by `iter_ids`,
 /// and must not fail with a [`DataErrorKind::IdentifierNotFound`] for requests that were returned.
 pub trait IterableDynamicDataProvider<M: DynamicDataMarker>: DynamicDataProvider<M> {
     /// Given a [`DataMarkerInfo`], returns a set of [`DataIdentifierCow`].
     fn iter_ids_for_marker(
         &self,
         marker: DataMarkerInfo,
     ) -> Result<BTreeSet<DataIdentifierCow>, DataError>;
 }

 impl<M, P> IterableDynamicDataProvider<M> for Box<P>
 where
     M: DynamicDataMarker,
     P: IterableDynamicDataProvider<M> + ?Sized,
 {
     fn iter_ids_for_marker(
         &self,
         marker: DataMarkerInfo,
     ) -> Result<BTreeSet<DataIdentifierCow>, DataError> {
         (**self).iter_ids_for_marker(marker)
     }
 }

 /// A data provider that loads data for a specific data type.
 ///
 /// Unlike [`DataProvider`], the provider is bound to a specific marker ahead of time.
 ///
 /// This crate provides [`DataProviderWithMarker`] which implements this trait on a single provider
 /// with a single marker. However, this trait can also be implemented on providers that fork between
 /// multiple markers that all return the same data type. For example, it can abstract over many
 /// calendar systems in the datetime formatter.
 ///
 /// [`AnyMarker`]: crate::any::AnyMarker
 pub trait BoundDataProvider<M>
 where
     M: DynamicDataMarker,
 {
     /// Query the provider for data, returning the result.
     ///
     /// Returns [`Ok`] if the request successfully loaded data. If data failed to load, returns an
     /// Error with more information.
     fn load_bound(&self, req: DataRequest) -> Result<DataResponse<M>, DataError>;
     /// Returns the [`DataMarkerInfo`] that this provider uses for loading data.
     fn bound_marker(&self) -> DataMarkerInfo;
 }

 impl<M, P> BoundDataProvider<M> for &P
 where
     M: DynamicDataMarker,
     P: BoundDataProvider<M> + ?Sized,
 {
     #[inline]
     fn load_bound(&self, req: DataRequest) -> Result<DataResponse<M>, DataError> {
         (*self).load_bound(req)
     }
     #[inline]
     fn bound_marker(&self) -> DataMarkerInfo {
         (*self).bound_marker()
     }
 }

 impl<M, P> BoundDataProvider<M> for Box<P>
 where
     M: DynamicDataMarker,
     P: BoundDataProvider<M> + ?Sized,
 {
     #[inline]
     fn load_bound(&self, req: DataRequest) -> Result<DataResponse<M>, DataError> {
         (**self).load_bound(req)
     }
     #[inline]
     fn bound_marker(&self) -> DataMarkerInfo {
         (**self).bound_marker()
     }
 }

 impl<M, P> BoundDataProvider<M> for alloc::rc::Rc<P>
 where
     M: DynamicDataMarker,
     P: BoundDataProvider<M> + ?Sized,
 {
     #[inline]
     fn load_bound(&self, req: DataRequest) -> Result<DataResponse<M>, DataError> {
         (**self).load_bound(req)
     }
     #[inline]
     fn bound_marker(&self) -> DataMarkerInfo {
         (**self).bound_marker()
     }
 }

 #[cfg(target_has_atomic = "ptr")]
 impl<M, P> BoundDataProvider<M> for alloc::sync::Arc<P>
 where
     M: DynamicDataMarker,
     P: BoundDataProvider<M> + ?Sized,
 {
     #[inline]
     fn load_bound(&self, req: DataRequest) -> Result<DataResponse<M>, DataError> {
         (**self).load_bound(req)
     }
     #[inline]
     fn bound_marker(&self) -> DataMarkerInfo {
         (**self).bound_marker()
     }
 }

 /// A [`DataProvider`] associated with a specific marker.
 ///
 /// Implements [`BoundDataProvider`].
 #[derive(Debug)]
 pub struct DataProviderWithMarker<M, P> {
     inner: P,
     _marker: PhantomData<M>,
 }

 impl<M, P> DataProviderWithMarker<M, P>
 where
     M: DataMarker,
     P: DataProvider<M>,
 {
     /// Creates a [`DataProviderWithMarker`] from a [`DataProvider`] with a [`DataMarker`].
     pub const fn new(inner: P) -> Self {
         Self {
             inner,
             _marker: PhantomData,
         }
     }
 }

 impl<M, M0, Y, P> BoundDataProvider<M0> for DataProviderWithMarker<M, P>
 where
     M: DataMarker<DataStruct = Y>,
     M0: DynamicDataMarker<DataStruct = Y>,
     Y: for<'a> Yokeable<'a>,
     P: DataProvider<M>,
 {
     #[inline]
     fn load_bound(&self, req: DataRequest) -> Result<DataResponse<M0>, DataError> {
         self.inner.load(req).map(DataResponse::cast)
     }
     #[inline]
     fn bound_marker(&self) -> DataMarkerInfo {
         M::INFO
     }
 }

 #[cfg(test)]
 mod test {

     use super::*;
     use crate::hello_world::*;
     use alloc::borrow::Cow;
     use alloc::string::String;
     use core::fmt::Debug;
     use serde::{Deserialize, Serialize};

     // This tests DataProvider borrow semantics with a dummy data provider based on a
     // JSON string. It also exercises most of the data provider code paths.

     /// Key for HelloAlt, used for testing mismatched types
     const HELLO_ALT_KEY: DataMarkerInfo =
         DataMarkerInfo::from_path(crate::marker::data_marker_path!("core/helloalt1@1"));

     /// A data struct serialization-compatible with HelloWorldV1 used for testing mismatched types
     #[derive(
         Serialize, Deserialize, Debug, Clone, Default, PartialEq, yoke::Yokeable, zerofrom::ZeroFrom,
     )]
     struct HelloAlt {
         #[zerofrom(clone)]
         message: String,
     }

     /// Marker type for [`HelloAlt`].
     struct HelloAltMarker {}

     impl DynamicDataMarker for HelloAltMarker {
         type DataStruct = HelloAlt;
     }

     impl DataMarker for HelloAltMarker {
         const INFO: DataMarkerInfo = HELLO_ALT_KEY;
     }

     #[derive(Deserialize, Debug, Clone, Default, PartialEq)]
     struct HelloCombined<'data> {
         #[serde(borrow)]
         pub hello_v1: HelloWorldV1<'data>,
         pub hello_alt: HelloAlt,
     }

     /// A DataProvider that owns its data, returning an Rc-variant DataPayload.
     /// Supports only key::HELLO_WORLD_V1. Uses `impl_dynamic_data_provider!()`.
     #[derive(Debug)]
     struct DataWarehouse {
         hello_v1: HelloWorldV1<'static>,
         hello_alt: HelloAlt,
     }

     impl DataProvider<HelloWorldV1Marker> for DataWarehouse {
         fn load(&self, _: DataRequest) -> Result<DataResponse<HelloWorldV1Marker>, DataError> {
             Ok(DataResponse {
                 metadata: DataResponseMetadata::default(),
                 payload: DataPayload::from_owned(self.hello_v1.clone()),
             })
         }
     }

     crate::dynutil::impl_dynamic_data_provider!(DataWarehouse, [HelloWorldV1Marker,], AnyMarker);

     /// A DataProvider that supports both key::HELLO_WORLD_V1 and HELLO_ALT.
     #[derive(Debug)]
     struct DataProvider2 {
         data: DataWarehouse,
     }

     impl From<DataWarehouse> for DataProvider2 {
         fn from(warehouse: DataWarehouse) -> Self {
             DataProvider2 { data: warehouse }
         }
     }

     impl DataProvider<HelloWorldV1Marker> for DataProvider2 {
         fn load(&self, _: DataRequest) -> Result<DataResponse<HelloWorldV1Marker>, DataError> {
             Ok(DataResponse {
                 metadata: DataResponseMetadata::default(),
                 payload: DataPayload::from_owned(self.data.hello_v1.clone()),
             })
         }
     }

     impl DataProvider<HelloAltMarker> for DataProvider2 {
         fn load(&self, _: DataRequest) -> Result<DataResponse<HelloAltMarker>, DataError> {
             Ok(DataResponse {
                 metadata: DataResponseMetadata::default(),
                 payload: DataPayload::from_owned(self.data.hello_alt.clone()),
             })
         }
     }

     crate::dynutil::impl_dynamic_data_provider!(
         DataProvider2,
         [HelloWorldV1Marker, HelloAltMarker,],
         AnyMarker
     );

     const DATA: &str = r#"{
         "hello_v1": {
             "message": "Hello V1"
         },
         "hello_alt": {
             "message": "Hello Alt"
         }
     }"#;

     fn get_warehouse(data: &'static str) -> DataWarehouse {
         let data: HelloCombined = serde_json::from_str(data).expect("Well-formed data");
         DataWarehouse {
             hello_v1: data.hello_v1,
             hello_alt: data.hello_alt,
         }
     }

     fn get_payload_v1<P: DataProvider<HelloWorldV1Marker> + ?Sized>(
         provider: &P,
     ) -> Result<DataPayload<HelloWorldV1Marker>, DataError> {
         provider.load(Default::default()).map(|r| r.payload)
     }

     fn get_payload_alt<P: DataProvider<HelloAltMarker> + ?Sized>(
         provider: &P,
     ) -> Result<DataPayload<HelloAltMarker>, DataError> {
         provider.load(Default::default()).map(|r| r.payload)
     }

     #[test]
     fn test_warehouse_owned() {
         let warehouse = get_warehouse(DATA);
         let hello_data = get_payload_v1(&warehouse).unwrap();
         assert!(matches!(
             hello_data.get(),
             HelloWorldV1 {
                 message: Cow::Borrowed(_),
             }
         ));
     }

     #[test]
     fn test_warehouse_owned_dyn_erased() {
         use crate::any::*;
         let warehouse = get_warehouse(DATA);
         let hello_data = get_payload_v1(&warehouse.as_any_provider().as_downcasting()).unwrap();
         assert!(matches!(
             hello_data.get(),
             HelloWorldV1 {
                 message: Cow::Borrowed(_),
             }
         ));
     }

     #[test]
     fn test_warehouse_owned_dyn_generic() {
         let warehouse = get_warehouse(DATA);
         let hello_data =
             get_payload_v1(&warehouse as &dyn DataProvider<HelloWorldV1Marker>).unwrap();
         assert!(matches!(
             hello_data.get(),
             HelloWorldV1 {
                 message: Cow::Borrowed(_),
             }
         ));
     }

     #[test]
     fn test_warehouse_owned_dyn_erased_alt() {
         let warehouse = get_warehouse(DATA);
         let response = get_payload_alt(&warehouse.as_any_provider().as_downcasting());
         assert!(matches!(
             response,
             Err(DataError {
                 kind: DataErrorKind::MarkerNotFound,
                 ..
             })
         ));
     }

     #[test]
     fn test_provider2() {
         let warehouse = get_warehouse(DATA);
         let provider = DataProvider2::from(warehouse);
         let hello_data = get_payload_v1(&provider).unwrap();
         assert!(matches!(
             hello_data.get(),
             HelloWorldV1 {
                 message: Cow::Borrowed(_),
             }
         ));
     }

     #[test]
     fn test_provider2_dyn_erased() {
         let warehouse = get_warehouse(DATA);
         let provider = DataProvider2::from(warehouse);
         let hello_data = get_payload_v1(&provider.as_any_provider().as_downcasting()).unwrap();
         assert!(matches!(
             hello_data.get(),
             HelloWorldV1 {
                 message: Cow::Borrowed(_),
             }
         ));
     }

     #[test]
     fn test_provider2_dyn_erased_alt() {
         let warehouse = get_warehouse(DATA);
         let provider = DataProvider2::from(warehouse);
         let hello_data = get_payload_alt(&provider.as_any_provider().as_downcasting()).unwrap();
         assert!(matches!(hello_data.get(), HelloAlt { .. }));
     }

     #[test]
     fn test_provider2_dyn_generic() {
         let warehouse = get_warehouse(DATA);
         let provider = DataProvider2::from(warehouse);
         let hello_data =
             get_payload_v1(&provider as &dyn DataProvider<HelloWorldV1Marker>).unwrap();
         assert!(matches!(
             hello_data.get(),
             HelloWorldV1 {
                 message: Cow::Borrowed(_),
             }
         ));
     }

     #[test]
     fn test_provider2_dyn_generic_alt() {
         let warehouse = get_warehouse(DATA);
         let provider = DataProvider2::from(warehouse);
         let hello_data = get_payload_alt(&provider as &dyn DataProvider<HelloAltMarker>).unwrap();
         assert!(matches!(hello_data.get(), HelloAlt { .. }));
     }

     #[test]
     fn test_mismatched_types() {
         let warehouse = get_warehouse(DATA);
         let provider = DataProvider2::from(warehouse);
         // Request is for v2, but type argument is for v1
         let response: Result<DataResponse<HelloWorldV1Marker>, DataError> = AnyProvider::load_any(
             &provider.as_any_provider(),
             HELLO_ALT_KEY,
             Default::default(),
         )
         .unwrap()
         .downcast();
         assert!(matches!(
             response,
             Err(DataError {
                 kind: DataErrorKind::Downcast(_),
                 ..
             })
         ));
     }

     fn check_v1_v2<P>(d: &P)
     where
         P: DataProvider<HelloWorldV1Marker> + DataProvider<HelloAltMarker> + ?Sized,
     {
         let v1: DataPayload<HelloWorldV1Marker> = d.load(Default::default()).unwrap().payload;
         let v2: DataPayload<HelloAltMarker> = d.load(Default::default()).unwrap().payload;
         if v1.get().message == v2.get().message {
             panic!()
         }
     }

     #[test]
     fn test_v1_v2_generic() {
         let warehouse = get_warehouse(DATA);
         let provider = DataProvider2::from(warehouse);
         check_v1_v2(&provider);
     }

     #[test]
     fn test_v1_v2_dyn_erased() {
         let warehouse = get_warehouse(DATA);
         let provider = DataProvider2::from(warehouse);
         check_v1_v2(&provider.as_any_provider().as_downcasting());
     }
 }
	// 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 ).

	use alloc::{boxed::Box, collections::BTreeSet};
	use core::marker::PhantomData;
	use yoke::Yokeable;

	use crate::prelude::*;

	/// A data provider that loads data for a specific [`DataMarkerInfo`].
	pub trait DataProvider<M>
	where
	M: DataMarker,
	{
	/// Query the provider for data, returning the result.
	///
	/// Returns [`Ok`] if the request successfully loaded data. If data failed to load, returns an
	/// Error with more information.
	fn load(&self, req: DataRequest) -> Result<DataResponse<M>, DataError>;
	}

	impl<M, P> DataProvider<M> for &P
	where
	M: DataMarker,
	P: DataProvider<M> + ?Sized,
	{
	#[inline]
	fn load(&self, req: DataRequest) -> Result<DataResponse<M>, DataError> {
	(*self).load(req)
	}
	}

	impl<M, P> DataProvider<M> for Box<P>
	where
	M: DataMarker,
	P: DataProvider<M> + ?Sized,
	{
	#[inline]
	fn load(&self, req: DataRequest) -> Result<DataResponse<M>, DataError> {
	(**self).load(req)
	}
	}

	impl<M, P> DataProvider<M> for alloc::rc::Rc<P>
	where
	M: DataMarker,
	P: DataProvider<M> + ?Sized,
	{
	#[inline]
	fn load(&self, req: DataRequest) -> Result<DataResponse<M>, DataError> {
	(**self).load(req)
	}
	}

	/// A [`DataProvider`] that can iterate over all supported [`DataIdentifierCow`]s.
	///
	/// The provider is not allowed to return `Ok` for requests that were not returned by `iter_ids`,
	/// and must not fail with a [`DataErrorKind::IdentifierNotFound`] for requests that were returned.
	pub trait IterableDataProvider<M: DataMarker>: DataProvider<M> {
	/// Returns a set of [`DataIdentifierCow`].
	fn iter_ids(&self) -> Result<BTreeSet<DataIdentifierCow>, DataError>;
	}

	#[cfg(target_has_atomic = "ptr")]
	impl<M, P> DataProvider<M> for alloc::sync::Arc<P>
	where
	M: DataMarker,
	P: DataProvider<M> + ?Sized,
	{
	#[inline]
	fn load(&self, req: DataRequest) -> Result<DataResponse<M>, DataError> {
	(**self).load(req)
	}
	}

	/// A data provider that can determine whether it can load a particular data identifier,
	/// potentially cheaper than actually performing the load.
	pub trait DryDataProvider<M: DataMarker>: DataProvider<M> {
	/// This method goes through the motions of [`load`], but only returns the metadata.
	///
	/// If `dry_load` returns an error, [`load`] must return the same error, but
	/// not vice-versa. Concretely, [`load`] could return deserialization or I/O errors
	/// that `dry_load` cannot predict.
	///
	/// [`load`]: DataProvider::load
	fn dry_load(&self, req: DataRequest) -> Result<DataResponseMetadata, 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.
	/// This is often the case when returning `dyn` trait objects such as [`AnyMarker`].
	///
	/// [`AnyMarker`]: crate::any::AnyMarker
	pub trait DynamicDataProvider<M>
	where
	M: DynamicDataMarker,
	{
	/// Query the provider for data, returning the result.
	///
	/// Returns [`Ok`] if the request successfully loaded data. If data failed to load, returns an
	/// Error with more information.
	fn load_data(
	&self,
	marker: DataMarkerInfo,
	req: DataRequest,
	) -> Result<DataResponse<M>, DataError>;
	}

	/// A dynanmic data provider that can determine whether it can load a particular data identifier,
	/// potentially cheaper than actually performing the load.
	pub trait DynamicDryDataProvider<M: DynamicDataMarker>: DynamicDataProvider<M> {
	/// This method goes through the motions of [`load_data`], but only returns the metadata.
	///
	/// If `dry_load_data` returns an error, [`load_data`] must return the same error, but
	/// not vice-versa. Concretely, [`load_data`] could return deserialization or I/O errors
	/// that `dry_load_data` cannot predict.
	///
	/// [`load_data`]: DynamicDataProvider::load_data
	fn dry_load_data(
	&self,
	marker: DataMarkerInfo,
	req: DataRequest,
	) -> Result<DataResponseMetadata, DataError>;
	}

	impl<M, P> DynamicDataProvider<M> for &P
	where
	M: DynamicDataMarker,
	P: DynamicDataProvider<M> + ?Sized,
	{
	#[inline]
	fn load_data(
	&self,
	marker: DataMarkerInfo,
	req: DataRequest,
	) -> Result<DataResponse<M>, DataError> {
	(*self).load_data(marker, req)
	}
	}

	impl<M, P> DynamicDataProvider<M> for Box<P>
	where
	M: DynamicDataMarker,
	P: DynamicDataProvider<M> + ?Sized,
	{
	#[inline]
	fn load_data(
	&self,
	marker: DataMarkerInfo,
	req: DataRequest,
	) -> Result<DataResponse<M>, DataError> {
	(**self).load_data(marker, req)
	}
	}

	impl<M, P> DynamicDataProvider<M> for alloc::rc::Rc<P>
	where
	M: DynamicDataMarker,
	P: DynamicDataProvider<M> + ?Sized,
	{
	#[inline]
	fn load_data(
	&self,
	marker: DataMarkerInfo,
	req: DataRequest,
	) -> Result<DataResponse<M>, DataError> {
	(**self).load_data(marker, req)
	}
	}

	#[cfg(target_has_atomic = "ptr")]
	impl<M, P> DynamicDataProvider<M> for alloc::sync::Arc<P>
	where
	M: DynamicDataMarker,
	P: DynamicDataProvider<M> + ?Sized,
	{
	#[inline]
	fn load_data(
	&self,
	marker: DataMarkerInfo,
	req: DataRequest,
	) -> Result<DataResponse<M>, DataError> {
	(**self).load_data(marker, req)
	}
	}

	/// A [`DynamicDataProvider`] that can iterate over all supported [`DataIdentifierCow`]s for a certain marker.
	///
	/// The provider is not allowed to return `Ok` for requests that were not returned by `iter_ids`,
	/// and must not fail with a [`DataErrorKind::IdentifierNotFound`] for requests that were returned.
	pub trait IterableDynamicDataProvider<M: DynamicDataMarker>: DynamicDataProvider<M> {
	/// Given a [`DataMarkerInfo`], returns a set of [`DataIdentifierCow`].
	fn iter_ids_for_marker(
	&self,
	marker: DataMarkerInfo,
	) -> Result<BTreeSet<DataIdentifierCow>, DataError>;
	}

	impl<M, P> IterableDynamicDataProvider<M> for Box<P>
	where
	M: DynamicDataMarker,
	P: IterableDynamicDataProvider<M> + ?Sized,
	{
	fn iter_ids_for_marker(
	&self,
	marker: DataMarkerInfo,
	) -> Result<BTreeSet<DataIdentifierCow>, DataError> {
	(**self).iter_ids_for_marker(marker)
	}
	}

	/// A data provider that loads data for a specific data type.
	///
	/// Unlike [`DataProvider`], the provider is bound to a specific marker ahead of time.
	///
	/// This crate provides [`DataProviderWithMarker`] which implements this trait on a single provider
	/// with a single marker. However, this trait can also be implemented on providers that fork between
	/// multiple markers that all return the same data type. For example, it can abstract over many
	/// calendar systems in the datetime formatter.
	///
	/// [`AnyMarker`]: crate::any::AnyMarker
	pub trait BoundDataProvider<M>
	where
	M: DynamicDataMarker,
	{
	/// Query the provider for data, returning the result.
	///
	/// Returns [`Ok`] if the request successfully loaded data. If data failed to load, returns an
	/// Error with more information.
	fn load_bound(&self, req: DataRequest) -> Result<DataResponse<M>, DataError>;
	/// Returns the [`DataMarkerInfo`] that this provider uses for loading data.
	fn bound_marker(&self) -> DataMarkerInfo;
	}

	impl<M, P> BoundDataProvider<M> for &P
	where
	M: DynamicDataMarker,
	P: BoundDataProvider<M> + ?Sized,
	{
	#[inline]
	fn load_bound(&self, req: DataRequest) -> Result<DataResponse<M>, DataError> {
	(*self).load_bound(req)
	}
	#[inline]
	fn bound_marker(&self) -> DataMarkerInfo {
	(*self).bound_marker()
	}
	}

	impl<M, P> BoundDataProvider<M> for Box<P>
	where
	M: DynamicDataMarker,
	P: BoundDataProvider<M> + ?Sized,
	{
	#[inline]
	fn load_bound(&self, req: DataRequest) -> Result<DataResponse<M>, DataError> {
	(**self).load_bound(req)
	}
	#[inline]
	fn bound_marker(&self) -> DataMarkerInfo {
	(**self).bound_marker()
	}
	}

	impl<M, P> BoundDataProvider<M> for alloc::rc::Rc<P>
	where
	M: DynamicDataMarker,
	P: BoundDataProvider<M> + ?Sized,
	{
	#[inline]
	fn load_bound(&self, req: DataRequest) -> Result<DataResponse<M>, DataError> {
	(**self).load_bound(req)
	}
	#[inline]
	fn bound_marker(&self) -> DataMarkerInfo {
	(**self).bound_marker()
	}
	}

	#[cfg(target_has_atomic = "ptr")]
	impl<M, P> BoundDataProvider<M> for alloc::sync::Arc<P>
	where
	M: DynamicDataMarker,
	P: BoundDataProvider<M> + ?Sized,
	{
	#[inline]
	fn load_bound(&self, req: DataRequest) -> Result<DataResponse<M>, DataError> {
	(**self).load_bound(req)
	}
	#[inline]
	fn bound_marker(&self) -> DataMarkerInfo {
	(**self).bound_marker()
	}
	}

	/// A [`DataProvider`] associated with a specific marker.
	///
	/// Implements [`BoundDataProvider`].
	#[derive(Debug)]
	pub struct DataProviderWithMarker<M, P> {
	inner: P,
	_marker: PhantomData<M>,
	}

	impl<M, P> DataProviderWithMarker<M, P>
	where
	M: DataMarker,
	P: DataProvider<M>,
	{
	/// Creates a [`DataProviderWithMarker`] from a [`DataProvider`] with a [`DataMarker`].
	pub const fn new(inner: P) -> Self {
	Self {
	inner,
	_marker: PhantomData,
	}
	}
	}

	impl<M, M0, Y, P> BoundDataProvider<M0> for DataProviderWithMarker<M, P>
	where
	M: DataMarker<DataStruct = Y>,
	M0: DynamicDataMarker<DataStruct = Y>,
	Y: for<'a> Yokeable<'a>,
	P: DataProvider<M>,
	{
	#[inline]
	fn load_bound(&self, req: DataRequest) -> Result<DataResponse<M0>, DataError> {
	self.inner.load(req).map(DataResponse::cast)
	}
	#[inline]
	fn bound_marker(&self) -> DataMarkerInfo {
	M::INFO
	}
	}

	#[cfg(test)]
	mod test {

	use super::*;
	use crate::hello_world::*;
	use alloc::borrow::Cow;
	use alloc::string::String;
	use core::fmt::Debug;
	use serde::{Deserialize, Serialize};

	// This tests DataProvider borrow semantics with a dummy data provider based on a
	// JSON string. It also exercises most of the data provider code paths.

	/// Key for HelloAlt, used for testing mismatched types
	const HELLO_ALT_KEY: DataMarkerInfo =
	DataMarkerInfo::from_path(crate::marker::data_marker_path!("core/helloalt1@1"));

	/// A data struct serialization-compatible with HelloWorldV1 used for testing mismatched types
	#[derive(
	Serialize, Deserialize, Debug, Clone, Default, PartialEq, yoke::Yokeable, zerofrom::ZeroFrom,
	)]
	struct HelloAlt {
	#[zerofrom(clone)]
	message: String,
	}

	/// Marker type for [`HelloAlt`].
	struct HelloAltMarker {}

	impl DynamicDataMarker for HelloAltMarker {
	type DataStruct = HelloAlt;
	}

	impl DataMarker for HelloAltMarker {
	const INFO: DataMarkerInfo = HELLO_ALT_KEY;
	}

	#[derive(Deserialize, Debug, Clone, Default, PartialEq)]
	struct HelloCombined<'data> {
	#[serde(borrow)]
	pub hello_v1: HelloWorldV1<'data>,
	pub hello_alt: HelloAlt,
	}

	/// A DataProvider that owns its data, returning an Rc-variant DataPayload.
	/// Supports only key::HELLO_WORLD_V1. Uses `impl_dynamic_data_provider!()`.
	#[derive(Debug)]
	struct DataWarehouse {
	hello_v1: HelloWorldV1<'static>,
	hello_alt: HelloAlt,
	}

	impl DataProvider<HelloWorldV1Marker> for DataWarehouse {
	fn load(&self, _: DataRequest) -> Result<DataResponse<HelloWorldV1Marker>, DataError> {
	Ok(DataResponse {
	metadata: DataResponseMetadata::default(),
	payload: DataPayload::from_owned(self.hello_v1.clone()),
	})
	}
	}

	crate::dynutil::impl_dynamic_data_provider!(DataWarehouse, [HelloWorldV1Marker,], AnyMarker);

	/// A DataProvider that supports both key::HELLO_WORLD_V1 and HELLO_ALT.
	#[derive(Debug)]
	struct DataProvider2 {
	data: DataWarehouse,
	}

	impl From<DataWarehouse> for DataProvider2 {
	fn from(warehouse: DataWarehouse) -> Self {
	DataProvider2 { data: warehouse }
	}
	}

	impl DataProvider<HelloWorldV1Marker> for DataProvider2 {
	fn load(&self, _: DataRequest) -> Result<DataResponse<HelloWorldV1Marker>, DataError> {
	Ok(DataResponse {
	metadata: DataResponseMetadata::default(),
	payload: DataPayload::from_owned(self.data.hello_v1.clone()),
	})
	}
	}

	impl DataProvider<HelloAltMarker> for DataProvider2 {
	fn load(&self, _: DataRequest) -> Result<DataResponse<HelloAltMarker>, DataError> {
	Ok(DataResponse {
	metadata: DataResponseMetadata::default(),
	payload: DataPayload::from_owned(self.data.hello_alt.clone()),
	})
	}
	}

	crate::dynutil::impl_dynamic_data_provider!(
	DataProvider2,
	[HelloWorldV1Marker, HelloAltMarker,],
	AnyMarker
	);

	const DATA: &str = r#"{
	"hello_v1": {
	"message": "Hello V1"
	},
	"hello_alt": {
	"message": "Hello Alt"
	}
	}"#;

	fn get_warehouse(data: &'static str) -> DataWarehouse {
	let data: HelloCombined = serde_json::from_str(data).expect("Well-formed data");
	DataWarehouse {
	hello_v1: data.hello_v1,
	hello_alt: data.hello_alt,
	}
	}

	fn get_payload_v1<P: DataProvider<HelloWorldV1Marker> + ?Sized>(
	provider: &P,
	) -> Result<DataPayload<HelloWorldV1Marker>, DataError> {
	provider.load(Default::default()).map(\|r\| r.payload)
	}

	fn get_payload_alt<P: DataProvider<HelloAltMarker> + ?Sized>(
	provider: &P,
	) -> Result<DataPayload<HelloAltMarker>, DataError> {
	provider.load(Default::default()).map(\|r\| r.payload)
	}

	#[test]
	fn test_warehouse_owned() {
	let warehouse = get_warehouse(DATA);
	let hello_data = get_payload_v1(&warehouse).unwrap();
	assert!(matches!(
	hello_data.get(),
	HelloWorldV1 {
	message: Cow::Borrowed(_),
	}
	));
	}

	#[test]
	fn test_warehouse_owned_dyn_erased() {
	use crate::any::*;
	let warehouse = get_warehouse(DATA);
	let hello_data = get_payload_v1(&warehouse.as_any_provider().as_downcasting()).unwrap();
	assert!(matches!(
	hello_data.get(),
	HelloWorldV1 {
	message: Cow::Borrowed(_),
	}
	));
	}

	#[test]
	fn test_warehouse_owned_dyn_generic() {
	let warehouse = get_warehouse(DATA);
	let hello_data =
	get_payload_v1(&warehouse as &dyn DataProvider<HelloWorldV1Marker>).unwrap();
	assert!(matches!(
	hello_data.get(),
	HelloWorldV1 {
	message: Cow::Borrowed(_),
	}
	));
	}

	#[test]
	fn test_warehouse_owned_dyn_erased_alt() {
	let warehouse = get_warehouse(DATA);
	let response = get_payload_alt(&warehouse.as_any_provider().as_downcasting());
	assert!(matches!(
	response,
	Err(DataError {
	kind: DataErrorKind::MarkerNotFound,
	..
	})
	));
	}

	#[test]
	fn test_provider2() {
	let warehouse = get_warehouse(DATA);
	let provider = DataProvider2::from(warehouse);
	let hello_data = get_payload_v1(&provider).unwrap();
	assert!(matches!(
	hello_data.get(),
	HelloWorldV1 {
	message: Cow::Borrowed(_),
	}
	));
	}

	#[test]
	fn test_provider2_dyn_erased() {
	let warehouse = get_warehouse(DATA);
	let provider = DataProvider2::from(warehouse);
	let hello_data = get_payload_v1(&provider.as_any_provider().as_downcasting()).unwrap();
	assert!(matches!(
	hello_data.get(),
	HelloWorldV1 {
	message: Cow::Borrowed(_),
	}
	));
	}

	#[test]
	fn test_provider2_dyn_erased_alt() {
	let warehouse = get_warehouse(DATA);
	let provider = DataProvider2::from(warehouse);
	let hello_data = get_payload_alt(&provider.as_any_provider().as_downcasting()).unwrap();
	assert!(matches!(hello_data.get(), HelloAlt { .. }));
	}

	#[test]
	fn test_provider2_dyn_generic() {
	let warehouse = get_warehouse(DATA);
	let provider = DataProvider2::from(warehouse);
	let hello_data =
	get_payload_v1(&provider as &dyn DataProvider<HelloWorldV1Marker>).unwrap();
	assert!(matches!(
	hello_data.get(),
	HelloWorldV1 {
	message: Cow::Borrowed(_),
	}
	));
	}

	#[test]
	fn test_provider2_dyn_generic_alt() {
	let warehouse = get_warehouse(DATA);
	let provider = DataProvider2::from(warehouse);
	let hello_data = get_payload_alt(&provider as &dyn DataProvider<HelloAltMarker>).unwrap();
	assert!(matches!(hello_data.get(), HelloAlt { .. }));
	}

	#[test]
	fn test_mismatched_types() {
	let warehouse = get_warehouse(DATA);
	let provider = DataProvider2::from(warehouse);
	// Request is for v2, but type argument is for v1
	let response: Result<DataResponse<HelloWorldV1Marker>, DataError> = AnyProvider::load_any(
	&provider.as_any_provider(),
	HELLO_ALT_KEY,
	Default::default(),
	)
	.unwrap()
	.downcast();
	assert!(matches!(
	response,
	Err(DataError {
	kind: DataErrorKind::Downcast(_),
	..
	})
	));
	}

	fn check_v1_v2<P>(d: &P)
	where
	P: DataProvider<HelloWorldV1Marker> + DataProvider<HelloAltMarker> + ?Sized,
	{
	let v1: DataPayload<HelloWorldV1Marker> = d.load(Default::default()).unwrap().payload;
	let v2: DataPayload<HelloAltMarker> = d.load(Default::default()).unwrap().payload;
	if v1.get().message == v2.get().message {
	panic!()
	}
	}

	#[test]
	fn test_v1_v2_generic() {
	let warehouse = get_warehouse(DATA);
	let provider = DataProvider2::from(warehouse);
	check_v1_v2(&provider);
	}

	#[test]
	fn test_v1_v2_dyn_erased() {
	let warehouse = get_warehouse(DATA);
	let provider = DataProvider2::from(warehouse);
	check_v1_v2(&provider.as_any_provider().as_downcasting());
	}
	}