Struct icu_provider::filter::RequestFilterDataProvider

pub struct RequestFilterDataProvider<D, F> where
    F: Fn(&DataRequest) -> bool,  {
    pub inner: D,
    pub predicate: F,
    pub description: String,
}

A data provider that selectively filters out data requests.

Data requests that are rejected by the filter will return DataError::FilteredResource, and they will not be returned by IterableDataProviderCore::supported_options_for_key.

Although this struct can be created directly, the traits in this module provide helper functions for common filtering patterns.

Fields

inner: D

The data provider to which we delegate requests.

predicate: F

The predicate function. A return value of true indicates that the request should proceed as normal; a return value of false will reject the request.

description: String

A description for this filter, used in error messages.

Implementations

impl<D, F> RequestFilterDataProvider<D, F> where
    F: Fn(&DataRequest) -> bool, 

pub fn filter_by_langid<'a>(
    self,
    predicate: impl Fn(&LanguageIdentifier) -> bool + 'a
) -> RequestFilterDataProvider<D, Box<dyn Fn(&DataRequest) -> bool + 'a>> where
    F: 'a, 

Filter out data requests with certain langids according to the predicate function. The predicate should return true to allow a langid and false to reject a langid.

Data requests with no langid will be allowed. To reject data requests without a langid, chain this with Self::require_langid.

Examples

use icu_provider::prelude::*;
use icu_provider::hello_world::*;
use icu_provider::filter::Filterable;
use icu_provider::iter::IterableDataProviderCore;
use icu_locid::LanguageIdentifier;
use icu_locid_macros::{language, langid};

let provider = HelloWorldProvider::new_with_placeholder_data()
    .filterable()
    .filter_by_langid(|langid| langid.language != language!("en"));

// German requests should succeed:
let req_de = DataRequest {
    resource_path: ResourcePath {
        key: key::HELLO_WORLD_V1,
        options: langid!("de").into(),
    }
};
let response: Result<DataResponse<HelloWorldV1Marker>, _> =
    provider.load_payload(&req_de);
assert!(matches!(response, Ok(_)));

// English requests should fail:
let req_en = DataRequest {
    resource_path: ResourcePath {
        key: key::HELLO_WORLD_V1,
        options: langid!("en-US").into(),
    }
};
let response: Result<DataResponse<HelloWorldV1Marker>, _> =
    provider.load_payload(&req_en);
assert!(matches!(response, Err(DataError::FilteredResource(_, _))));

// English should not appear in the iterator result:
let supported_langids = provider.supported_options_for_key(&key::HELLO_WORLD_V1)
    .expect("Should successfully make an iterator of supported locales")
    .filter_map(|options| options.langid)
    .collect::<Vec<LanguageIdentifier>>();
assert!(supported_langids.contains(&langid!("de")));
assert!(!supported_langids.contains(&langid!("en")));

pub fn filter_by_langid_with_description<'a>(
    self,
    predicate: impl Fn(&LanguageIdentifier) -> bool + 'a,
    description: String
) -> RequestFilterDataProvider<D, Box<dyn Fn(&DataRequest) -> bool + 'a>> where
    F: 'a, 

Same as Self::filter_by_langid but with an extra argument to set a custom description for debugging.

pub fn filter_by_langid_allowlist_strict<'a>(
    self,
    allowlist: &'a [LanguageIdentifier]
) -> RequestFilterDataProvider<D, Box<dyn Fn(&DataRequest) -> bool + 'a>> where
    F: 'a, 

Filter out data request except those having a language identifier that exactly matches one in the allowlist.

This will be replaced with a smarter algorithm for locale filtering; see https://github.com/unicode-org/icu4x/issues/834

Data requests with no langid will be allowed. To reject data requests without a langid, chain this with Self::require_langid.

Examples

use icu_provider::prelude::*;
use icu_provider::hello_world::*;
use icu_provider::filter::Filterable;
use icu_locid_macros::langid;

let allowlist = vec![langid!("de"), langid!("zh")];
let provider = HelloWorldProvider::new_with_placeholder_data()
    .filterable()
    .filter_by_langid_allowlist_strict(&allowlist);

// German requests should succeed:
let req_de = DataRequest {
    resource_path: ResourcePath {
        key: key::HELLO_WORLD_V1,
        options: langid!("de").into(),
    }
};
let response: Result<DataResponse<HelloWorldV1Marker>, _> =
    provider.load_payload(&req_de);
assert!(matches!(response, Ok(_)));

// English requests should fail:
let req_en = DataRequest {
    resource_path: ResourcePath {
        key: key::HELLO_WORLD_V1,
        options: langid!("en-US").into(),
    }
};
let response: Result<DataResponse<HelloWorldV1Marker>, _> =
    provider.load_payload(&req_en);
assert!(matches!(response, Err(DataError::FilteredResource(_, _))));
assert_eq!(
    "Resource was filtered: Locale filter (allowlist: [de, zh]): core/helloworld@1/en-US",
    response.unwrap_err().to_string()
);

pub fn require_langid<'a>(
    self
) -> RequestFilterDataProvider<D, Box<dyn Fn(&DataRequest) -> bool + 'a>> where
    F: 'a, 

Require that data requests contain a langid.

Examples

use icu_provider::prelude::*;
use icu_provider::hello_world::*;
use icu_provider::filter::Filterable;
use icu_locid_macros::langid;

let provider = HelloWorldProvider::new_with_placeholder_data()
    .filterable()
    .require_langid();

// Requests with a langid should succeed:
let req_with_langid = DataRequest {
    resource_path: ResourcePath {
        key: key::HELLO_WORLD_V1,
        options: langid!("de").into(),
    }
};
let response: Result<DataResponse<HelloWorldV1Marker>, _> =
    provider.load_payload(&req_with_langid);
assert!(matches!(response, Ok(_)));

// Requests without a langid should fail:
let req_no_langid = DataRequest {
    resource_path: ResourcePath {
        key: key::HELLO_WORLD_V1,
        options: Default::default(),
    }
};
let response: Result<DataResponse<HelloWorldV1Marker>, _> =
    provider.load_payload(&req_no_langid);
assert!(matches!(response, Err(DataError::FilteredResource(_, _))));

Trait Implementations

impl<'data, D, F, M> DataProvider<'data, M> for RequestFilterDataProvider<D, F> where
    F: Fn(&DataRequest) -> bool,
    M: DataMarker<'data>,
    D: DataProvider<'data, M>, 

fn load_payload(
    &self,
    req: &DataRequest
) -> Result<DataResponse<'data, M>, DataError>

Query the provider for data, returning the result.

impl<D, F> IterableDataProviderCore for RequestFilterDataProvider<D, F> where
    F: Fn(&DataRequest) -> bool,
    D: IterableDataProviderCore, 

fn supported_options_for_key(
    &self,
    resc_key: &ResourceKey
) -> Result<Box<dyn Iterator<Item = ResourceOptions>>, DataError>

Given a ResourceKey, returns a boxed iterator over ResourceOptions.