Adds GetFeatureNamesAsync to IVariantFeatureManager and uses the inte…

…rface in FeatureManagerSnapshot (#270)

src/Microsoft.FeatureManagement/FeatureManager.cs

@@ -13,6 +13,7 @@
 using System.Collections.Generic;
 using System.Diagnostics;
 using System.Linq;
+using System.Runtime.CompilerServices;
 using System.Threading;
 using System.Threading.Tasks;
 
@@ -145,11 +146,18 @@ private async Task<bool> IsEnabledWithVariantsAsync<TContext>(string feature, TC
             return isFeatureEnabled;
         }
 
-        public async IAsyncEnumerable<string> GetFeatureNamesAsync()
+        public IAsyncEnumerable<string> GetFeatureNamesAsync()
         {
-            await foreach (FeatureDefinition featureDefintion in _featureDefinitionProvider.GetAllFeatureDefinitionsAsync().ConfigureAwait(false))
+            return GetFeatureNamesAsync(CancellationToken.None);
+        }
+
+        public async IAsyncEnumerable<string> GetFeatureNamesAsync([EnumeratorCancellation] CancellationToken cancellationToken)
+        {
+            await foreach (FeatureDefinition featureDefinition in _featureDefinitionProvider.GetAllFeatureDefinitionsAsync().ConfigureAwait(false))
             {
-                yield return featureDefintion.Name;
+                cancellationToken.ThrowIfCancellationRequested();
+
+                yield return featureDefinition.Name;
             }
         }
 

src/Microsoft.FeatureManagement/FeatureManagerSnapshot.cs

@@ -5,6 +5,7 @@
 using System;
 using System.Collections.Concurrent;
 using System.Collections.Generic;
+using System.Runtime.CompilerServices;
 using System.Threading;
 using System.Threading.Tasks;
 
@@ -15,23 +16,28 @@ namespace Microsoft.FeatureManagement
     /// </summary>
     class FeatureManagerSnapshot : IFeatureManagerSnapshot, IVariantFeatureManagerSnapshot
     {
-        private readonly FeatureManager _featureManager;
+        private readonly IVariantFeatureManager _featureManager;
         private readonly ConcurrentDictionary<string, Task<bool>> _flagCache = new ConcurrentDictionary<string, Task<bool>>();
         private readonly ConcurrentDictionary<string, Variant> _variantCache = new ConcurrentDictionary<string, Variant>();
         private IEnumerable<string> _featureNames;
 
-        public FeatureManagerSnapshot(FeatureManager featureManager)
+        public FeatureManagerSnapshot(IVariantFeatureManager featureManager)
         {
             _featureManager = featureManager ?? throw new ArgumentNullException(nameof(featureManager));
         }
 
-        public async IAsyncEnumerable<string> GetFeatureNamesAsync()
+        public IAsyncEnumerable<string> GetFeatureNamesAsync()
+        {
+            return GetFeatureNamesAsync(CancellationToken.None);
+        }
+
+        public async IAsyncEnumerable<string> GetFeatureNamesAsync([EnumeratorCancellation] CancellationToken cancellationToken)
         {
             if (_featureNames == null)
             {
                 var featureNames = new List<string>();
 
-                await foreach (string featureName in _featureManager.GetFeatureNamesAsync().ConfigureAwait(false))
+                await foreach (string featureName in _featureManager.GetFeatureNamesAsync(cancellationToken).ConfigureAwait(false))
                 {
                     featureNames.Add(featureName);
                 }
@@ -49,28 +55,28 @@ public Task<bool> IsEnabledAsync(string feature)
         {
             return _flagCache.GetOrAdd(
                 feature,
-                (key) => _featureManager.IsEnabledAsync(key));
+                (key) => _featureManager.IsEnabledAsync(key, CancellationToken.None));
         }
 
         public Task<bool> IsEnabledAsync<TContext>(string feature, TContext context)
         {
             return _flagCache.GetOrAdd(
                 feature,
-                (key) => _featureManager.IsEnabledAsync(key, context));
+                (key) => _featureManager.IsEnabledAsync(key, context, CancellationToken.None));
         }
 
         public Task<bool> IsEnabledAsync(string feature, CancellationToken cancellationToken)
         {
             return _flagCache.GetOrAdd(
                 feature,
-                (key) => _featureManager.IsEnabledAsync(key));
+                (key) => _featureManager.IsEnabledAsync(key, cancellationToken));
         }
 
         public Task<bool> IsEnabledAsync<TContext>(string feature, TContext context, CancellationToken cancellationToken)
         {
             return _flagCache.GetOrAdd(
                 feature,
-                (key) => _featureManager.IsEnabledAsync(key, context));
+                (key) => _featureManager.IsEnabledAsync(key, context, cancellationToken));
         }
 
         public async ValueTask<Variant> GetVariantAsync(string feature, CancellationToken cancellationToken)

src/Microsoft.FeatureManagement/IVariantFeatureManager.cs

@@ -4,6 +4,7 @@
 using System.Threading.Tasks;
 using System.Threading;
 using Microsoft.FeatureManagement.FeatureFilters;
+using System.Collections.Generic;
 
 namespace Microsoft.FeatureManagement
 {
@@ -12,6 +13,12 @@ namespace Microsoft.FeatureManagement
     /// </summary>
     public interface IVariantFeatureManager
     {
+        /// <summary>
+        /// Retrieves a list of feature names registered in the feature manager.
+        /// </summary>
+        /// <returns>An enumerator which provides asynchronous iteration over the feature names registered in the feature manager.</returns>
+        IAsyncEnumerable<string> GetFeatureNamesAsync(CancellationToken cancellationToken);
+
         /// <summary>
         /// Checks whether a given feature is enabled.
         /// </summary>
@@ -30,15 +37,15 @@ public interface IVariantFeatureManager
         Task<bool> IsEnabledAsync<TContext>(string feature, TContext context, CancellationToken cancellationToken);
 
         /// <summary>
-        /// Gets the assigned variant for a specfic feature.
+        /// Gets the assigned variant for a specific feature.
         /// </summary>
         /// <param name="feature">The name of the feature to evaluate.</param>
         /// <param name="cancellationToken">The cancellation token to cancel the operation.</param>
         /// <returns>A variant assigned to the user based on the feature's configured allocation.</returns>
         ValueTask<Variant> GetVariantAsync(string feature, CancellationToken cancellationToken);
 
         /// <summary>
-        /// Gets the assigned variant for a specfic feature.
+        /// Gets the assigned variant for a specific feature.
         /// </summary>
         /// <param name="feature">The name of the feature to evaluate.</param>
         /// <param name="context">An instance of <see cref="TargetingContext"/> used to evaluate which variant the user will be assigned.</param>