feat: enhance singleton and tests

Signed-off-by: YUE Daian <[email protected]>

README.md

@@ -22,5 +22,8 @@ TBD
 
 ## Pending Feature List
 
-- [ ] Provider hooks (2.3.*)
-
+- Some requirements of Flag Evaluation API.
+- Provider hooks (2.3)
+- Evaluation context levels and merging (3.2)
+- Hooks (4)
+- Events (5)

src/api/api.rs

@@ -1,4 +1,4 @@
-use std::sync::{Arc, RwLock};
+use std::sync::{Arc, RwLock, RwLockReadGuard, RwLockWriteGuard};
 
 use lazy_static::lazy_static;
 
@@ -24,6 +24,14 @@ pub struct OpenFeature {
 }
 
 impl OpenFeature {
+    pub fn singleton() -> RwLockReadGuard<'static, Self> {
+        SINGLETON.read().unwrap()
+    }
+
+    pub fn singleton_mut() -> RwLockWriteGuard<'static, Self> {
+        SINGLETON.write().unwrap()
+    }
+
     pub fn set_provider<T>(&mut self, provider: T)
     where
         T: FeatureProvider,
@@ -46,6 +54,8 @@ impl OpenFeature {
 
 #[cfg(test)]
 mod tests {
+    use std::thread;
+
     use super::*;
     use crate::provider::*;
 
@@ -69,4 +79,26 @@ mod tests {
 
         assert_eq!(true, value);
     }
+
+    #[tokio::test]
+    async fn test_singleton_multi_thread() {
+        let reader1 = thread::spawn(|| {
+            let _ = OpenFeature::singleton().provider_metadata();
+        });
+
+        let writer = thread::spawn(|| {
+            OpenFeature::singleton_mut().set_provider(FixedValueProvider::default());
+        });
+
+        let reader2 = thread::spawn(|| {
+            let _ = OpenFeature::singleton().provider_metadata();
+        });
+
+        let _ = (reader1.join(), reader2.join(), writer.join());
+
+        assert_eq!(
+            "Fixed Value",
+            OpenFeature::singleton().provider_metadata().name
+        );
+    }
 }

src/provider/feature_provider.rs

@@ -95,7 +95,7 @@ pub trait FeatureProvider: Send + Sync + 'static {
 #[derive(Clone, TypedBuilder, Default, Debug)]
 pub struct ProviderMetadata {
     #[builder(setter(into))]
-    name: String,
+    pub name: String,
 }
 
 impl ProviderMetadata {