add testcases

src/Microsoft.FeatureManagement/ConfigurationFeatureDefinitionProvider.cs

@@ -218,17 +218,28 @@ private IEnumerable<IConfigurationSection> GetDotnetFeatureDefinitionSections()
 
         private IEnumerable<IConfigurationSection> GetMicrosoftFeatureDefinitionSections()
         {
-            var configurationRoot = _configuration as IConfigurationRoot;
-            if (configurationRoot == null)
+            var featureDefinitionSections = new List<IConfigurationSection>();
+
+            FindFeatureFlags(_configuration, featureDefinitionSections);
+
+            return featureDefinitionSections;
+        }
+
+        private void FindFeatureFlags(IConfiguration configuration, List<IConfigurationSection> featureDefinitionSections)
+        {
+            if (!(configuration is IConfigurationRoot configurationRoot))
             {
-                // Fallback to current behavior if not an IConfigurationRoot
-                return _configuration
+                IConfigurationSection featureFlagsSection = configuration
                     .GetSection(MicrosoftFeatureManagementFields.FeatureManagementSectionName)
-                    .GetSection(MicrosoftFeatureManagementFields.FeatureFlagsSectionName)
-                    .GetChildren();
-            }
+                    .GetSection(MicrosoftFeatureManagementFields.FeatureFlagsSectionName);
 
-            var mergedSections = new List<IConfigurationSection>();
+                if (featureFlagsSection.Exists())
+                {
+                    featureDefinitionSections.AddRange(featureFlagsSection.GetChildren());
+                }
+
+                return;
+            }
 
             foreach (IConfigurationProvider provider in configurationRoot.Providers)
             {
@@ -248,18 +259,14 @@ private IEnumerable<IConfigurationSection> GetMicrosoftFeatureDefinitionSections
 
                     if (featureFlagsSection.Exists())
                     {
-                        mergedSections.AddRange(featureFlagsSection.GetChildren());
+                        featureDefinitionSections.AddRange(featureFlagsSection.GetChildren());
                     }
                 }
                 else if (provider is ChainedConfigurationProvider chainedProvider)
                 {
-                    IConfigurationSection featureFlagsSection = chainedProvider.Configuration
-                        .GetSection(MicrosoftFeatureManagementFields.FeatureManagementSectionName)
-                        .GetSection(MicrosoftFeatureManagementFields.FeatureFlagsSectionName);
+                    FindFeatureFlags(chainedProvider.Configuration, featureDefinitionSections);
                 }
             }
-
-            return mergedSections;
         }
 
         private FeatureDefinition ParseDotnetSchemaFeatureDefinition(IConfigurationSection configurationSection)

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>
@@ -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
+      }
+    ]
+  }
+}