Merge feature flags from different configuration source

src/Microsoft.FeatureManagement/ConfigurationFeatureDefinitionProvider.cs

@@ -22,8 +22,9 @@ public sealed class ConfigurationFeatureDefinitionProvider : IFeatureDefinitionP
         //
         // IFeatureDefinitionProviderCacheable interface is only used to mark this provider as cacheable. This allows our test suite's
         // provider to be marked for caching as well.
-
         private readonly IConfiguration _configuration;
+        private IEnumerable<IConfigurationSection> _dotnetFeatureDefinitionSections;
+        private IEnumerable<IConfigurationSection> _microsoftFeatureDefinitionSections;
         private readonly ConcurrentDictionary<string, Task<FeatureDefinition>> _definitions;
         private IDisposable _changeSubscription;
         private int _stale = 0;
@@ -48,6 +49,10 @@ public ConfigurationFeatureDefinitionProvider(IConfiguration configuration)
             {
                 return Task.FromResult(GetMicrosoftSchemaFeatureDefinition(featureName) ?? GetDotnetSchemaFeatureDefinition(featureName));
             };
+
+            _dotnetFeatureDefinitionSections = GetDotnetFeatureDefinitionSections();
+
+            _microsoftFeatureDefinitionSections = GetMicrosoftFeatureDefinitionSections();
         }
 
         /// <summary>
@@ -90,6 +95,10 @@ public Task<FeatureDefinition> GetFeatureDefinitionAsync(string featureName)
             if (Interlocked.Exchange(ref _stale, 0) != 0)
             {
                 _definitions.Clear();
+
+                _dotnetFeatureDefinitionSections = GetDotnetFeatureDefinitionSections();
+
+                _microsoftFeatureDefinitionSections = GetMicrosoftFeatureDefinitionSections();
             }
 
             return _definitions.GetOrAdd(featureName, _getFeatureDefinitionFunc);
@@ -109,11 +118,13 @@ public async IAsyncEnumerable<FeatureDefinition> GetAllFeatureDefinitionsAsync()
             if (Interlocked.Exchange(ref _stale, 0) != 0)
             {
                 _definitions.Clear();
-            }
 
-            IEnumerable<IConfigurationSection> microsoftFeatureDefinitionSections = GetMicrosoftFeatureDefinitionSections();
+                _dotnetFeatureDefinitionSections = GetDotnetFeatureDefinitionSections();
+
+                _microsoftFeatureDefinitionSections = GetMicrosoftFeatureDefinitionSections();
+            }
 
-            foreach (IConfigurationSection featureSection in microsoftFeatureDefinitionSections)
+            foreach (IConfigurationSection featureSection in _microsoftFeatureDefinitionSections)
             {
                 string featureName = featureSection[MicrosoftFeatureManagementFields.Id];
 
@@ -132,9 +143,7 @@ public async IAsyncEnumerable<FeatureDefinition> GetAllFeatureDefinitionsAsync()
                 }
             }
 
-            IEnumerable<IConfigurationSection> dotnetFeatureDefinitionSections = GetDotnetFeatureDefinitionSections();
-
-            foreach (IConfigurationSection featureSection in dotnetFeatureDefinitionSections)
+            foreach (IConfigurationSection featureSection in _dotnetFeatureDefinitionSections)
             {
                 string featureName = featureSection.Key;
 
@@ -156,9 +165,7 @@ public async IAsyncEnumerable<FeatureDefinition> GetAllFeatureDefinitionsAsync()
 
         private FeatureDefinition GetDotnetSchemaFeatureDefinition(string featureName)
         {
-            IEnumerable<IConfigurationSection> dotnetFeatureDefinitionSections = GetDotnetFeatureDefinitionSections();
-
-            IConfigurationSection dotnetFeatureDefinitionConfiguration = dotnetFeatureDefinitionSections
+            IConfigurationSection dotnetFeatureDefinitionConfiguration = _dotnetFeatureDefinitionSections
                 .FirstOrDefault(section =>
                     string.Equals(section.Key, featureName, StringComparison.OrdinalIgnoreCase));
 
@@ -172,9 +179,7 @@ private FeatureDefinition GetDotnetSchemaFeatureDefinition(string featureName)
 
         private FeatureDefinition GetMicrosoftSchemaFeatureDefinition(string featureName)
         {
-            IEnumerable<IConfigurationSection> microsoftFeatureDefinitionSections = GetMicrosoftFeatureDefinitionSections();
-
-            IConfigurationSection microsoftFeatureDefinitionConfiguration = microsoftFeatureDefinitionSections
+            IConfigurationSection microsoftFeatureDefinitionConfiguration = _microsoftFeatureDefinitionSections
                 .LastOrDefault(section =>
                     string.Equals(section[MicrosoftFeatureManagementFields.Id], featureName, StringComparison.OrdinalIgnoreCase));
 
@@ -211,9 +216,55 @@ private IEnumerable<IConfigurationSection> GetDotnetFeatureDefinitionSections()
 
         private IEnumerable<IConfigurationSection> GetMicrosoftFeatureDefinitionSections()
         {
-            return _configuration.GetSection(MicrosoftFeatureManagementFields.FeatureManagementSectionName)
-                .GetSection(MicrosoftFeatureManagementFields.FeatureFlagsSectionName)
-                .GetChildren();
+            var featureDefinitionSections = new List<IConfigurationSection>();
+
+            FindFeatureFlags(_configuration, featureDefinitionSections);
+
+            return featureDefinitionSections;
+        }
+
+        private void FindFeatureFlags(IConfiguration configuration, List<IConfigurationSection> featureDefinitionSections)
+        {
+            if (!(configuration is IConfigurationRoot configurationRoot) ||
+                configurationRoot.Providers.Any(provider =>
+                    !(provider is ConfigurationProvider) && !(provider is ChainedConfigurationProvider)))
+            {
+                IConfigurationSection featureFlagsSection = configuration
+                    .GetSection(MicrosoftFeatureManagementFields.FeatureManagementSectionName)
+                    .GetSection(MicrosoftFeatureManagementFields.FeatureFlagsSectionName);
+
+                if (featureFlagsSection.Exists())
+                {
+                    featureDefinitionSections.AddRange(featureFlagsSection.GetChildren());
+                }
+
+                return;
+            }
+
+            foreach (IConfigurationProvider provider in configurationRoot.Providers)
+            {
+                if (provider is ConfigurationProvider configurationProvider)
+                {
+                    //
+                    // Cannot use the original provider directly as its reload token is subscribed
+                    var onDemandConfigurationProvider = new OnDemandConfigurationProvider(configurationProvider);
+
+                    var onDemandConfigurationRoot = new ConfigurationRoot(new[] { onDemandConfigurationProvider });
+
+                    IConfigurationSection featureFlagsSection = onDemandConfigurationRoot
+                        .GetSection(MicrosoftFeatureManagementFields.FeatureManagementSectionName)
+                        .GetSection(MicrosoftFeatureManagementFields.FeatureFlagsSectionName);
+
+                    if (featureFlagsSection.Exists())
+                    {
+                        featureDefinitionSections.AddRange(featureFlagsSection.GetChildren());
+                    }
+                }
+                else if (provider is ChainedConfigurationProvider chainedProvider)
+                {
+                    FindFeatureFlags(chainedProvider.Configuration, featureDefinitionSections);
+                }
+            }
         }
 
         private FeatureDefinition ParseDotnetSchemaFeatureDefinition(IConfigurationSection configurationSection)

src/Microsoft.FeatureManagement/Microsoft.FeatureManagement.csproj

@@ -41,9 +41,10 @@
 
   <ItemGroup>
     <PackageReference Include="Microsoft.Bcl.TimeProvider" Version="8.0.1" />
-    <PackageReference Include="Microsoft.Extensions.Caching.Memory" Version="2.1.23" />
-    <PackageReference Include="Microsoft.Extensions.Configuration.Binder" Version="2.1.10" />
-    <PackageReference Include="Microsoft.Extensions.Logging" Version="2.1.1" />
+    <PackageReference Include="Microsoft.Extensions.Caching.Memory" Version="8.0.1" />
+    <PackageReference Include="Microsoft.Extensions.Configuration" Version="8.0.0" />
+    <PackageReference Include="Microsoft.Extensions.Configuration.Binder" Version="8.0.2" />
+    <PackageReference Include="Microsoft.Extensions.Logging" Version="8.0.1" />
     <PackageReference Include="System.Diagnostics.DiagnosticSource" Version="8.0.1" />
   </ItemGroup>
 

src/Microsoft.FeatureManagement/OnDemandConfigurationProvider.cs

@@ -0,0 +1,18 @@
+using Microsoft.Extensions.Configuration;
+using System.Collections.Generic;
+using System.Reflection;
+
+namespace Microsoft.FeatureManagement
+{
+    internal class OnDemandConfigurationProvider : ConfigurationProvider
+    {
+        private static readonly PropertyInfo _DataProperty = typeof(ConfigurationProvider).GetProperty(nameof(Data), BindingFlags.NonPublic | BindingFlags.Instance);
+
+        public OnDemandConfigurationProvider(ConfigurationProvider configurationProvider)
+        {
+            var data = _DataProperty.GetValue(configurationProvider) as IDictionary<string, string>;
+
+            Data = data;
+        }
+    }
+}

tests/Tests.FeatureManagement.AspNetCore/Tests.FeatureManagement.AspNetCore.csproj

@@ -24,14 +24,14 @@
     <PackageReference Include="Microsoft.AspNetCore.TestHost" Version="8.0.1" />
     <PackageReference Include="Microsoft.Extensions.Configuration.Json" Version="8.0.0" />
     <PackageReference Include="System.Text.Json" Version="8.0.5" />
-    <PackageReference Include="Microsoft.Extensions.DependencyInjection" Version="8.0.0" />
+    <PackageReference Include="Microsoft.Extensions.DependencyInjection" Version="8.0.1" />
   </ItemGroup>
 
   <ItemGroup Condition="'$(TargetFramework)' == 'net9.0'">
     <PackageReference Include="Microsoft.AspNetCore.TestHost" Version="8.0.1" />
     <PackageReference Include="Microsoft.Extensions.Configuration.Json" Version="8.0.0" />
     <PackageReference Include="System.Text.Json" Version="8.0.5" />
-    <PackageReference Include="Microsoft.Extensions.DependencyInjection" Version="8.0.0" />
+    <PackageReference Include="Microsoft.Extensions.DependencyInjection" Version="8.0.1" />
   </ItemGroup>
 
   <ItemGroup>

tests/Tests.FeatureManagement/FeatureManagementTest.cs

@@ -394,6 +394,50 @@ public async Task LastFeatureFlagWins()
 
             Assert.True(await featureManager.IsEnabledAsync(Features.DuplicateFlag));
         }
+
+        [Fact]
+        public async Task MergesFeatureFlagsFromDifferentConfigurationSources()
+        {
+            /*
+             * appsettings1.json
+             * Feature1: true
+             * Feature2: true
+             * FeatureA: true
+             * 
+             * appsettings2.json
+             * Feature1: true
+             * Feature2: false
+             * FeatureB: true
+             * 
+             * appsettings3.json
+             * Feature1: false
+             * Feature2: false
+             * FeatureC: true
+             */
+
+            IConfiguration configuration1 = new ConfigurationBuilder()
+                .AddJsonFile("appsettings1.json")
+                .AddJsonFile("appsettings2.json")
+                .Build();
+
+            IConfiguration configuration2 = new ConfigurationBuilder()
+                .AddConfiguration(configuration1) // chained configuration
+                .AddJsonFile("appsettings3.json")
+                .Build();
+
+            var featureManager1 = new FeatureManager(new ConfigurationFeatureDefinitionProvider(configuration1));
+            Assert.True(await featureManager1.IsEnabledAsync("FeatureA"));
+            Assert.True(await featureManager1.IsEnabledAsync("FeatureB"));
+            Assert.True(await featureManager1.IsEnabledAsync("Feature1"));
+            Assert.False(await featureManager1.IsEnabledAsync("Feature2")); // appsettings2 should override appsettings1
+
+            var featureManager2 = new FeatureManager(new ConfigurationFeatureDefinitionProvider(configuration2));
+            Assert.True(await featureManager2.IsEnabledAsync("FeatureA"));
+            Assert.True(await featureManager2.IsEnabledAsync("FeatureB"));
+            Assert.True(await featureManager2.IsEnabledAsync("FeatureC"));
+            Assert.False(await featureManager2.IsEnabledAsync("Feature1")); // appsettings3 should override previous settings
+            Assert.False(await featureManager2.IsEnabledAsync("Feature2")); // appsettings3 should override previous settings
+        }
     }
 
     public class FeatureManagementFeatureFilterGeneralTest

tests/Tests.FeatureManagement/Tests.FeatureManagement.csproj

@@ -1,4 +1,4 @@
-<Project Sdk="Microsoft.NET.Sdk">
+<Project Sdk="Microsoft.NET.Sdk">
 
   <PropertyGroup>
     <TargetFrameworks>net48;net8.0;net9.0</TargetFrameworks>
@@ -18,21 +18,21 @@
   <ItemGroup Condition="'$(TargetFramework)' == 'net48'">
     <PackageReference Include="Microsoft.Extensions.Configuration.EnvironmentVariables" Version="3.1.32" />
     <PackageReference Include="Microsoft.Extensions.Configuration.Json" Version="3.1.32" />
-    <PackageReference Include="Microsoft.Extensions.DependencyInjection" Version="8.0.0" />
+    <PackageReference Include="Microsoft.Extensions.DependencyInjection" Version="8.0.1" />
   </ItemGroup>
 
   <ItemGroup Condition="'$(TargetFramework)' == 'net8.0'">
     <PackageReference Include="Microsoft.Extensions.Configuration.EnvironmentVariables" Version="8.0.0" />
     <PackageReference Include="Microsoft.Extensions.Configuration.Json" Version="8.0.0" />
     <PackageReference Include="System.Text.Json" Version="8.0.5" />
-    <PackageReference Include="Microsoft.Extensions.DependencyInjection" Version="8.0.0" />
+    <PackageReference Include="Microsoft.Extensions.DependencyInjection" Version="8.0.1" />
   </ItemGroup>
 
   <ItemGroup Condition="'$(TargetFramework)' == 'net9.0'">
     <PackageReference Include="Microsoft.Extensions.Configuration.EnvironmentVariables" Version="8.0.0" />
     <PackageReference Include="Microsoft.Extensions.Configuration.Json" Version="8.0.0" />
     <PackageReference Include="System.Text.Json" Version="8.0.5" />
-    <PackageReference Include="Microsoft.Extensions.DependencyInjection" Version="8.0.0" />
+    <PackageReference Include="Microsoft.Extensions.DependencyInjection" Version="8.0.1" />
   </ItemGroup>
 
   <ItemGroup>
@@ -43,6 +43,15 @@
     <None Update="appsettings.json">
       <CopyToOutputDirectory>Always</CopyToOutputDirectory>
     </None>
+    <None Update="appsettings1.json">
+      <CopyToOutputDirectory>Always</CopyToOutputDirectory>
+    </None>
+    <None Update="appsettings2.json">
+      <CopyToOutputDirectory>Always</CopyToOutputDirectory>
+    </None>
+    <None Update="appsettings3.json">
+      <CopyToOutputDirectory>Always</CopyToOutputDirectory>
+    </None>
     <None Update="DotnetFeatureManagementSchema.json">
       <CopyToOutputDirectory>Always</CopyToOutputDirectory>
     </None>

tests/Tests.FeatureManagement/appsettings1.json

@@ -0,0 +1,18 @@
+{
+  "feature_management": {
+    "feature_flags": [
+      {
+        "id": "Feature1",
+        "enabled": true
+      },
+      {
+        "id": "Feature2",
+        "enabled": true
+      },
+      {
+        "id": "FeatureA",
+        "enabled": true
+      }
+    ]
+  }
+}

tests/Tests.FeatureManagement/appsettings2.json

@@ -0,0 +1,18 @@
+{
+    "feature_management": {
+        "feature_flags": [
+            {
+                "id": "Feature1",
+                "enabled": true
+            },
+            {
+                "id": "Feature2",
+                "enabled": false
+            },
+            {
+                "id": "FeatureB",
+                "enabled": true
+            }
+        ]
+    }
+}

tests/Tests.FeatureManagement/appsettings3.json

@@ -0,0 +1,18 @@
+{
+  "feature_management": {
+    "feature_flags": [
+      {
+        "id": "Feature1",
+        "enabled": false
+      },
+      {
+        "id": "Feature2",
+        "enabled": false
+      },
+      {
+        "id": "FeatureC",
+        "enabled": true
+      }
+    ]
+  }
+}