fix: Address issue with FeatureClient not being resolved when no Provider added (#607)

* Fix issue with FeatureClient not being resolved

* Address issue when adding context to the feature builder without
  providing any provider or default feature client.

Signed-off-by: Kyle Julian <[email protected]>

* Add unit test for bug

Signed-off-by: Kyle Julian <[email protected]>

* Run dotnet format

Signed-off-by: Kyle Julian <[email protected]>

* Address Gemini comment

Signed-off-by: Kyle Julian <[email protected]>

---------

Signed-off-by: Kyle Julian <[email protected]>

Author: kylejuliandev

src/OpenFeature.Hosting/OpenFeatureServiceCollectionExtensions.cs

@@ -30,6 +30,7 @@ public static IServiceCollection AddOpenFeature(this IServiceCollection services
         var builder = new OpenFeatureBuilder(services);
         configure(builder);
 
+        builder.Services.Configure<OpenFeatureOptions>(c => { }); // Ensures IOptions<OpenFeatureOptions> is available even when no providers are configured.
         builder.Services.AddHostedService<HostedFeatureLifecycleService>();
 
         // If a default provider is specified without additional providers,
@@ -50,7 +51,7 @@ public static IServiceCollection AddOpenFeature(this IServiceCollection services
                 options.DefaultNameSelector = provider =>
                 {
                     var options = provider.GetRequiredService<IOptions<OpenFeatureOptions>>().Value;
-                    return options.ProviderNames.First();
+                    return options.ProviderNames.FirstOrDefault();
                 };
             });
         }

test/OpenFeature.Hosting.Tests/OpenFeatureServiceCollectionExtensionsTests.cs

@@ -92,4 +92,16 @@ public void AddOpenFeature_WithNamedDefaultProvider_InvokesAddPolicyName()
         var otherClient = serviceProvider.GetService<IFeatureClient>();
         Assert.NotNull(otherClient);
     }
+
+    [Fact]
+    public void AddOpenFeature_WithNoProvider_CanResolveFeatureClient()
+    {
+        // Act
+        _systemUnderTest.AddOpenFeature(builder => { });
+
+        // Assert
+        using var serviceProvider = _systemUnderTest.BuildServiceProvider();
+        var client = serviceProvider.GetService<IFeatureClient>();
+        Assert.NotNull(client);
+    }
 }