dedup same selectors with original precedence (#494)

src/Microsoft.Extensions.Configuration.AzureAppConfiguration/AzureAppConfigurationOptions.cs

@@ -166,15 +166,11 @@ public AzureAppConfigurationOptions Select(string keyFilter, string labelFilter
                 throw new ArgumentException("The characters '*' and ',' are not supported in label filters.", nameof(labelFilter));
             }
 
-            if (!_kvSelectors.Any(s => string.Equals(s.KeyFilter, keyFilter) && string.Equals(s.LabelFilter, labelFilter)))
+            _kvSelectors.AppendUnique(new KeyValueSelector
             {
-                _kvSelectors.Add(new KeyValueSelector
-                {
-                    KeyFilter = keyFilter,
-                    LabelFilter = labelFilter
-                });
-            }
-
+                KeyFilter = keyFilter,
+                LabelFilter = labelFilter
+            });
             return this;
         }
 
@@ -190,13 +186,10 @@ public AzureAppConfigurationOptions SelectSnapshot(string name)
                 throw new ArgumentNullException(nameof(name));
             }
 
-            if (!_kvSelectors.Any(s => string.Equals(s.SnapshotName, name)))
+            _kvSelectors.AppendUnique(new KeyValueSelector
             {
-                _kvSelectors.Add(new KeyValueSelector
-                {
-                    SnapshotName = name
-                });
-            }
+                SnapshotName = name
+            });
 
             return this;
         }
@@ -222,43 +215,32 @@ public AzureAppConfigurationOptions UseFeatureFlags(Action<FeatureFlagOptions> c
             {
                 throw new InvalidOperationException($"Please select feature flags by either the {nameof(options.Select)} method or by setting the {nameof(options.Label)} property, not both.");
             }
-            
+
             if (options.FeatureFlagSelectors.Count() == 0)
             {
                 // Select clause is not present
                 options.FeatureFlagSelectors.Add(new KeyValueSelector
                 {
                     KeyFilter = FeatureManagementConstants.FeatureFlagMarker + "*",
                     LabelFilter = options.Label == null ? LabelFilter.Null : options.Label
-                });  
+                });
             }
 
             foreach (var featureFlagSelector in options.FeatureFlagSelectors)
             {
                 var featureFlagFilter = featureFlagSelector.KeyFilter;
                 var labelFilter = featureFlagSelector.LabelFilter;
 
-                if (!_kvSelectors.Any(selector => selector.KeyFilter == featureFlagFilter && selector.LabelFilter == labelFilter))
-                {
-                    Select(featureFlagFilter, labelFilter);
-                }
-
-                var multiKeyWatcher = _multiKeyWatchers.FirstOrDefault(kw => kw.Key.Equals(featureFlagFilter) && kw.Label.NormalizeNull() == labelFilter.NormalizeNull());
+                Select(featureFlagFilter, labelFilter);
 
-                if (multiKeyWatcher == null)
-                {
-                    _multiKeyWatchers.Add(new KeyValueWatcher
-                    {
-                        Key = featureFlagFilter,
-                        Label = labelFilter,
-                        CacheExpirationInterval = options.CacheExpirationInterval
-                    });
-                }
-                else
+                _multiKeyWatchers.AppendUnique(new KeyValueWatcher
                 {
+                    Key = featureFlagFilter,
+                    Label = labelFilter,
                     // If UseFeatureFlags is called multiple times for the same key and label filters, last cache expiration time wins
-                    multiKeyWatcher.CacheExpirationInterval = options.CacheExpirationInterval;
-                }
+                    CacheExpirationInterval = options.CacheExpirationInterval
+                });
+
             }
 
             return this;

src/Microsoft.Extensions.Configuration.AzureAppConfiguration/Extensions/ListExtensions.cs

@@ -0,0 +1,31 @@
+// Copyright (c) Microsoft Corporation.
+// Licensed under the MIT license.
+//
+using System;
+using System.Collections.Generic;
+using System.Linq;
+
+namespace Microsoft.Extensions.Configuration.AzureAppConfiguration.Extensions
+{
+    internal static class ListExtensions
+    {
+        public static void AppendUnique<T>(this List<T> items, T item)
+        {
+            if (item == null)
+            {
+                throw new ArgumentNullException(nameof(item));
+            }
+
+            T existingItem = items.FirstOrDefault(s => Equals(s, item));
+
+            if (existingItem != null)
+            {
+                // Remove duplicate item if existing.
+                items.Remove(existingItem);
+            }
+
+            // Append to the end, keeping precedence.
+            items.Add(item);
+        }
+    }
+}

src/Microsoft.Extensions.Configuration.AzureAppConfiguration/FeatureManagement/FeatureFlagOptions.cs

@@ -2,6 +2,7 @@
 // Licensed under the MIT license.
 //
 using Microsoft.Extensions.Configuration.AzureAppConfiguration.Models;
+using Microsoft.Extensions.Configuration.AzureAppConfiguration.Extensions;
 using System;
 using System.Collections.Generic;
 using System.Linq;
@@ -67,14 +68,11 @@ public FeatureFlagOptions Select(string featureFlagFilter, string labelFilter =
 
             string featureFlagPrefix = FeatureManagementConstants.FeatureFlagMarker + featureFlagFilter;
 
-            if (!FeatureFlagSelectors.Any(s => s.KeyFilter.Equals(featureFlagPrefix) && s.LabelFilter.Equals(labelFilter)))
+            FeatureFlagSelectors.AppendUnique(new KeyValueSelector
             {
-                FeatureFlagSelectors.Add(new KeyValueSelector
-                {
-                    KeyFilter = featureFlagPrefix,
-                    LabelFilter = labelFilter
-                });
-            }
+                KeyFilter = featureFlagPrefix,
+                LabelFilter = labelFilter
+            });
 
             return this;
         }

src/Microsoft.Extensions.Configuration.AzureAppConfiguration/Models/KeyValueSelector.cs

@@ -23,5 +23,33 @@ public class KeyValueSelector
         /// The name of the Azure App Configuration snapshot to use when selecting key-values for the configuration provider.
         /// </summary>
         public string SnapshotName { get; set; }
+
+        /// <summary>
+        /// Determines whether the specified object is equal to the current object.
+        /// </summary>
+        /// <param name="obj">The object to compare with the current object.</param>
+        /// <returns>true if the specified object is equal to the current object; otherwise, false.</returns>
+        public override bool Equals(object obj)
+        {
+            if (obj is KeyValueSelector selector)
+            {
+                return KeyFilter == selector.KeyFilter
+                    && LabelFilter == selector.LabelFilter
+                    && SnapshotName == selector.SnapshotName;
+            }
+
+            return false;
+        }
+
+        /// <summary>
+        /// Serves as the hash function.
+        /// </summary>
+        /// <returns>A hash code for the current object.</returns>
+        public override int GetHashCode()
+        {
+            return (KeyFilter?.GetHashCode() ?? 0) ^
+                   (LabelFilter?.GetHashCode() ?? 1) ^
+                   (SnapshotName?.GetHashCode() ?? 2);
+        }
     }
 }

src/Microsoft.Extensions.Configuration.AzureAppConfiguration/Models/KeyValueWatcher.cs

@@ -1,6 +1,7 @@
 // Copyright (c) Microsoft Corporation.
 // Licensed under the MIT license.
 //
+using Microsoft.Extensions.Configuration.AzureAppConfiguration.Extensions;
 using System;
 
 namespace Microsoft.Extensions.Configuration.AzureAppConfiguration.Models
@@ -36,7 +37,7 @@ public override bool Equals(object obj)
         {
             if (obj is KeyValueWatcher kvWatcher)
             {
-                return Key == kvWatcher.Key && Label == kvWatcher.Label;
+                return Key == kvWatcher.Key && Label.NormalizeNull() == kvWatcher.Label.NormalizeNull();
             }
 
             return false;

tests/Tests.AzureAppConfiguration/FeatureManagementTests.cs

@@ -518,6 +518,41 @@ public void MultipleSelectsInSameUseFeatureFlags()
             Assert.Null(config["FeatureManagement:Feature1"]);
         }
 
+        [Fact]
+        public void KeepSelectorPrecedenceAfterDedup()
+        {
+            var mockResponse = new Mock<Response>();
+            var mockClient = new Mock<ConfigurationClient>(MockBehavior.Strict);
+            var prefix = "Feature1";
+            var label1 = "App1_Label";
+            var label2 = "App2_Label";
+
+            mockClient.Setup(c => c.GetConfigurationSettingsAsync(It.IsAny<SettingSelector>(), It.IsAny<CancellationToken>()))
+                .Returns(() =>
+                {
+                    return new MockAsyncPageable(_featureFlagCollection.Where(s =>
+                        (s.Key.StartsWith(FeatureManagementConstants.FeatureFlagMarker + prefix) && s.Label == label1) ||
+                        (s.Key.StartsWith(FeatureManagementConstants.FeatureFlagMarker + prefix) && s.Label == label2)).ToList());
+                });
+
+            var testClient = mockClient.Object;
+
+            var config = new ConfigurationBuilder()
+                .AddAzureAppConfiguration(options =>
+                {
+                    options.ClientManager = TestHelpers.CreateMockedConfigurationClientManager(testClient);
+                    options.UseFeatureFlags(ff =>
+                    {
+                        ff.Select(prefix + "*", label1); // to be deduped
+                        ff.Select(prefix + "*", label2); // lower precedence
+                        ff.Select(prefix + "*", label1); // higher precedence, taking effect
+                    });
+                })
+                .Build();
+            // label: App1_Label has higher precedence
+            Assert.Equal("True", config["FeatureManagement:Feature1"]);
+        }
+
         [Fact]
         public void UseFeatureFlagsThrowsIfBothSelectAndLabelPresent()
         {

tests/Tests.AzureAppConfiguration/Tests.cs

@@ -315,5 +315,36 @@ public void TestTurnOffRequestTracing()
             // Delete the azure function environment variable
             Environment.SetEnvironmentVariable(RequestTracingConstants.AzureFunctionEnvironmentVariable, null);
         }
+
+        [Fact]
+        public void TestKeepSelectorPrecedenceAfterDedup()
+        {
+            var mockResponse = new Mock<Response>();
+            var mockClient = new Mock<ConfigurationClient>(MockBehavior.Strict);
+            var kvOfDevLabel = new List<ConfigurationSetting>
+            {
+                ConfigurationModelFactory.ConfigurationSetting("message", "message from dev label", "dev")
+            };
+            var kvOfProdLabel = new List<ConfigurationSetting>
+            {
+                ConfigurationModelFactory.ConfigurationSetting("message", "message from prod label", "prod")
+            };
+            mockClient.Setup(c => c.GetConfigurationSettingsAsync(It.Is<SettingSelector>(s => s.LabelFilter == "dev"), It.IsAny<CancellationToken>()))
+                .Returns(new MockAsyncPageable(kvOfDevLabel));
+            mockClient.Setup(c => c.GetConfigurationSettingsAsync(It.Is<SettingSelector>(s => s.LabelFilter == "prod"), It.IsAny<CancellationToken>()))
+                .Returns(new MockAsyncPageable(kvOfProdLabel));
+
+            var config = new ConfigurationBuilder()
+                .AddAzureAppConfiguration(options =>
+                {
+                    options.ClientManager = TestHelpers.CreateMockedConfigurationClientManager(mockClient.Object);
+                    options.Select("message", "dev");
+                    options.Select("message", "prod");
+                    options.Select("message", "dev");
+                })
+                .Build();
+
+            Assert.True(config["message"] == "message from dev label");
+        }
     }
 }