Using factory for provider creation

OpenFeature.sln

@@ -36,7 +36,7 @@ Project("{9A19103F-16F7-4668-BE54-9A1E7A4F7556}") = "OpenFeature.Tests", "test\O
 EndProject
 Project("{9A19103F-16F7-4668-BE54-9A1E7A4F7556}") = "OpenFeature.Benchmarks", "test\OpenFeature.Benchmarks\OpenFeature.Benchmarks.csproj", "{90E7EAD3-251E-4490-AF78-E758E33518E5}"
 EndProject
-Project("{9A19103F-16F7-4668-BE54-9A1E7A4F7556}") = "OpenFeature.E2ETests", "test\OpenFeature.E2ETests\OpenFeature.E2ETests.csproj", "{90E7EAD3-251E-4490-AF78-E758E33518E5}"
+Project("{9A19103F-16F7-4668-BE54-9A1E7A4F7556}") = "OpenFeature.E2ETests", "test\OpenFeature.E2ETests\OpenFeature.E2ETests.csproj", "{CB82B298-040A-4E8B-B74E-1636DC5C2457}"
 EndProject
 Global
 	GlobalSection(SolutionConfigurationPlatforms) = preSolution
@@ -56,6 +56,10 @@ Global
 		{90E7EAD3-251E-4490-AF78-E758E33518E5}.Debug|Any CPU.Build.0 = Debug|Any CPU
 		{90E7EAD3-251E-4490-AF78-E758E33518E5}.Release|Any CPU.ActiveCfg = Release|Any CPU
 		{90E7EAD3-251E-4490-AF78-E758E33518E5}.Release|Any CPU.Build.0 = Release|Any CPU
+		{CB82B298-040A-4E8B-B74E-1636DC5C2457}.Debug|Any CPU.ActiveCfg = Debug|Any CPU
+		{CB82B298-040A-4E8B-B74E-1636DC5C2457}.Debug|Any CPU.Build.0 = Debug|Any CPU
+		{CB82B298-040A-4E8B-B74E-1636DC5C2457}.Release|Any CPU.ActiveCfg = Release|Any CPU
+		{CB82B298-040A-4E8B-B74E-1636DC5C2457}.Release|Any CPU.Build.0 = Release|Any CPU
 	EndGlobalSection
 	GlobalSection(SolutionProperties) = preSolution
 		HideSolutionNode = FALSE

src/OpenFeature/Api.cs

@@ -1,3 +1,4 @@
+using System;
 using System.Collections.Concurrent;
 using System.Collections.Generic;
 using System.Linq;
@@ -15,9 +16,9 @@ namespace OpenFeature
     public sealed class Api
     {
         private EvaluationContext _evaluationContext = EvaluationContext.Empty;
-        private FeatureProvider _defaultProvider = new NoOpFeatureProvider();
-        private readonly ConcurrentDictionary<string, FeatureProvider> _featureProviders =
-            new ConcurrentDictionary<string, FeatureProvider>();
+        private Func<FeatureProvider> _defaultProviderFunc = () => new NoOpFeatureProvider();
+        private readonly ConcurrentDictionary<string, Func<FeatureProvider>> _featureProviders =
+            new ConcurrentDictionary<string, Func<FeatureProvider>> ();
         private readonly ConcurrentStack<Hook> _hooks = new ConcurrentStack<Hook>();
 
         /// The reader/writer locks are not disposed because the singleton instance should never be disposed.
@@ -44,7 +45,7 @@ public void SetProvider(FeatureProvider featureProvider)
             this._featureProviderLock.EnterWriteLock();
             try
             {
-                this._defaultProvider = featureProvider ?? this._defaultProvider;
+                this._defaultProviderFunc = featureProvider != null ? () => featureProvider : this._defaultProviderFunc;
             }
             finally
             {
@@ -59,8 +60,37 @@ public void SetProvider(FeatureProvider featureProvider)
         /// <param name="featureProvider">Implementation of <see cref="FeatureProvider"/></param>
         public void SetProvider(string clientName, FeatureProvider featureProvider)
         {
-            this._featureProviders.AddOrUpdate(clientName, featureProvider,
-                (key, current) => featureProvider);
+            FeatureProvider func() => featureProvider;
+            this._featureProviders.AddOrUpdate(clientName, func,
+                (key, current) => func);
+        }
+
+        /// <summary>
+        /// Sets the feature provider
+        /// </summary>
+        /// <param name="featureProviderFactory">A function to create new <see cref="FeatureProvider"/></param>
+        public void SetProvider(Func<FeatureProvider> featureProviderFactory)
+        {
+            this._featureProviderLock.EnterWriteLock();
+            try
+            {
+                this._defaultProviderFunc = featureProviderFactory ?? this._defaultProviderFunc;
+            }
+            finally
+            {
+                this._featureProviderLock.ExitWriteLock();
+            }
+        }
+
+        /// <summary>
+        /// Sets the feature provider to given clientName
+        /// </summary>
+        /// <param name="clientName">Name of client</param>
+        /// <param name="featureProviderFactory">A function to create new <see cref="FeatureProvider"/></param>
+        public void SetProvider(string clientName, Func<FeatureProvider> featureProviderFactory)
+        {
+            this._featureProviders.AddOrUpdate(clientName, featureProviderFactory,
+                (key, current) => featureProviderFactory);
         }
 
         /// <summary>
@@ -79,7 +109,7 @@ public FeatureProvider GetProvider()
             this._featureProviderLock.EnterReadLock();
             try
             {
-                return this._defaultProvider;
+                return this._defaultProviderFunc();
             }
             finally
             {
@@ -100,8 +130,8 @@ public FeatureProvider GetProvider(string clientName)
                 return this.GetProvider();
             }
 
-            return this._featureProviders.TryGetValue(clientName, out var featureProvider)
-                ? featureProvider
+            return this._featureProviders.TryGetValue(clientName, out var featureProviderFunc)
+                ? featureProviderFunc()
                 : this.GetProvider();
         }
 

src/OpenFeature/OpenFeatureClient.cs

@@ -23,6 +23,7 @@ public sealed class FeatureClient : IFeatureClient
         private EvaluationContext _evaluationContext;
 
         private readonly object _evaluationContextLock = new object();
+        private FeatureProvider _featureProvider;
 
         /// <summary>
         /// Get a provider and an associated typed flag resolution method.
@@ -40,11 +41,10 @@ public sealed class FeatureClient : IFeatureClient
             ExtractProvider<T>(
                 Func<FeatureProvider, Func<string, T, EvaluationContext, Task<ResolutionDetails<T>>>> method)
         {
-            // Alias the provider reference so getting the method and returning the provider are
-            // guaranteed to be the same object.
-            var provider = Api.Instance.GetProvider(this._metadata.Name);
+            // Will use factory to get provider if it's not created for this client.
+            this._featureProvider = this._featureProvider ?? Api.Instance.GetProvider(this._metadata.Name);
 
-            return (method(provider), provider);
+            return (method(this._featureProvider), this._featureProvider);
         }
 
         /// <inheritdoc />

test/OpenFeature.Tests/OpenFeatureClientTests.cs

@@ -351,7 +351,7 @@ public async Task When_Exception_Occurs_During_Evaluation_Should_Return_Error()
         [Fact]
         public async Task Should_Use_No_Op_When_Provider_Is_Null()
         {
-            Api.Instance.SetProvider(null);
+            Api.Instance.SetProvider((FeatureProvider)null);
             var client = new FeatureClient("test", "test");
             (await client.GetIntegerValue("some-key", 12)).Should().Be(12);
         }