From ab1a28bde02bfe732d82c71be2ee99a530cd2dbe Mon Sep 17 00:00:00 2001
From: Jimmy Campbell <jimmyca@microsoft.com>
Date: Tue, 7 Jun 2022 17:23:52 -0700
Subject: [PATCH] Throw exception if feature management schemas are mixed to
 avoid unintentionally hiding feature flags.

---
 .../ConfigurationDynamicFeatureDefinitionProvider.cs |  2 +-
 .../ConfigurationFeatureFlagDefinitionProvider.cs    | 12 ++++++++++++
 .../FeatureManagementError.cs                        |  7 ++++++-
 3 files changed, 19 insertions(+), 2 deletions(-)

diff --git a/src/Microsoft.FeatureManagement/ConfigurationDynamicFeatureDefinitionProvider.cs b/src/Microsoft.FeatureManagement/ConfigurationDynamicFeatureDefinitionProvider.cs
index 82794ef6..4c50702e 100644
--- a/src/Microsoft.FeatureManagement/ConfigurationDynamicFeatureDefinitionProvider.cs
+++ b/src/Microsoft.FeatureManagement/ConfigurationDynamicFeatureDefinitionProvider.cs
@@ -19,8 +19,8 @@ namespace Microsoft.FeatureManagement
     /// </summary>
     sealed class ConfigurationDynamicFeatureDefinitionProvider : IDynamicFeatureDefinitionProvider, IDisposable
     {
+        public const string DynamicFeatureDefinitionsSectionName = "DynamicFeatures";
         private const string FeatureManagementSectionName = "FeatureManagement";
-        private const string DynamicFeatureDefinitionsSectionName= "DynamicFeatures";
         private const string FeatureVariantsSectionName = "Variants";
         private readonly IConfiguration _configuration;
         private readonly ConcurrentDictionary<string, DynamicFeatureDefinition> _dynamicFeatureDefinitions;
diff --git a/src/Microsoft.FeatureManagement/ConfigurationFeatureFlagDefinitionProvider.cs b/src/Microsoft.FeatureManagement/ConfigurationFeatureFlagDefinitionProvider.cs
index d302cff2..e3aea38d 100644
--- a/src/Microsoft.FeatureManagement/ConfigurationFeatureFlagDefinitionProvider.cs
+++ b/src/Microsoft.FeatureManagement/ConfigurationFeatureFlagDefinitionProvider.cs
@@ -186,6 +186,18 @@ private IEnumerable<IConfigurationSection> GetFeatureFlagDefinitionSections()
 
             IConfigurationSection featureFlagsSection = featureManagementChildren.FirstOrDefault(s => s.Key == FeatureFlagDefinitionsSectionName);
 
+            //
+            // Check for mixed schema to avoid confusing scenario where feature flags defined in separate sources with different schemas don't mix.
+            if (featureFlagsSection != null &&
+                featureManagementChildren.Any(section =>
+                    !section.Key.Equals(FeatureFlagDefinitionsSectionName) &&
+                    !section.Key.Equals(ConfigurationDynamicFeatureDefinitionProvider.DynamicFeatureDefinitionsSectionName)))
+            {
+                throw new FeatureManagementException(
+                    FeatureManagementError.InvalidConfiguration,
+                    "Detected feature flags defined using different feature management schemas.");
+            }
+
             //
             // Support backward compatability where feature flag definitions were directly under the feature management section
             return featureFlagsSection == null ?
diff --git a/src/Microsoft.FeatureManagement/FeatureManagementError.cs b/src/Microsoft.FeatureManagement/FeatureManagementError.cs
index 8eb6208a..a8deb232 100644
--- a/src/Microsoft.FeatureManagement/FeatureManagementError.cs
+++ b/src/Microsoft.FeatureManagement/FeatureManagementError.cs
@@ -61,6 +61,11 @@ public enum FeatureManagementError
         /// <summary>
         /// A dynamic feature does not have a default feature variant configured.
         /// </summary>
-        MissingDefaultFeatureVariant
+        MissingDefaultFeatureVariant,
+
+        /// <summary>
+        /// A configuration error is present in the feature management system.
+        /// </summary>
+        InvalidConfiguration
     }
 }