Add support for filtering by tags

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

@@ -346,6 +346,7 @@ await ExecuteWithFailOverPolicyAsync(clients, async (client) =>
                             {
                                 KeyFilter = watcher.Key,
                                 LabelFilter = watcher.Label,
+                                TagFilters = watcher.Tags,
                                 IsFeatureFlagSelector = true
                             }),
                             _ffEtags,
@@ -828,6 +829,14 @@ private async Task<Dictionary<string, ConfigurationSetting>> LoadSelected(
                         LabelFilter = loadOption.LabelFilter
                     };
 
+                    if (loadOption.TagFilters != null)
+                    {
+                        foreach (string tagFilter in loadOption.TagFilters)
+                        {
+                            selector.TagsFilter.Add(tagFilter);
+                        }
+                    }
+
                     var matchConditions = new List<MatchConditions>();
 
                     await CallWithRequestTracing(async () =>

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

@@ -74,7 +74,14 @@ public FeatureFlagOptions SetRefreshInterval(TimeSpan refreshInterval)
         /// The label filter to apply when querying Azure App Configuration for feature flags. By default the null label will be used. Built-in label filter options: <see cref="LabelFilter"/>
         /// The characters asterisk (*) and comma (,) are not supported. Backslash (\) character is reserved and must be escaped using another backslash (\).
         /// </param>
-        public FeatureFlagOptions Select(string featureFlagFilter, string labelFilter = LabelFilter.Null)
+        /// <param name="tagFilters">
+        /// In addition to key and label filters, feature flags from Azure App Configuration can be filtered based on their tag names and values.
+        /// Each tag filter must follow the format "tagName=tagValue". Only those feature flags will be loaded whose tags match all the tags provided here.
+        /// Built in tag filter values: <see cref="TagValue"/>. For example, $"tagName={<see cref="TagValue.Null"/>}".
+        /// The characters asterisk (*), comma (,) and backslash (\) are reserved and must be escaped using a backslash (\).
+        /// Up to 5 tag filters can be provided. If no tag filters are provided, feature flags will not be filtered based on tags.
+        /// </param>
+        public FeatureFlagOptions Select(string featureFlagFilter, string labelFilter = LabelFilter.Null, IEnumerable<string> tagFilters = null)
         {
             if (string.IsNullOrEmpty(featureFlagFilter))
             {
@@ -97,12 +104,24 @@ public FeatureFlagOptions Select(string featureFlagFilter, string labelFilter =
                 throw new ArgumentException("The characters '*' and ',' are not supported in label filters.", nameof(labelFilter));
             }
 
+            if (tagFilters != null)
+            {
+                foreach (string tag in tagFilters)
+                {
+                    if (string.IsNullOrEmpty(tag) || !tag.Contains('=') || tag.IndexOf('=') == 0)
+                    {
+                        throw new ArgumentException($"Tag filter '{tag}' does not follow the format \"tagName=tagValue\".", nameof(tagFilters));
+                    }
+                }
+            }
+
             string featureFlagPrefix = FeatureManagementConstants.FeatureFlagMarker + featureFlagFilter;
 
             FeatureFlagSelectors.AppendUnique(new KeyValueSelector
             {
                 KeyFilter = featureFlagPrefix,
                 LabelFilter = labelFilter,
+                TagFilters = tagFilters,
                 IsFeatureFlagSelector = true
             });
 

src/Microsoft.Extensions.Configuration.AzureAppConfiguration/Microsoft.Extensions.Configuration.AzureAppConfiguration.csproj

@@ -15,10 +15,12 @@
   </PropertyGroup>
 
   <ItemGroup>
-    <PackageReference Include="Azure.Data.AppConfiguration" Version="1.4.1" />
+    <PackageReference Include="Azure.Data.AppConfiguration" Version="1.6.0" />
     <PackageReference Include="Azure.Messaging.EventGrid" Version="4.7.0" />
     <PackageReference Include="Azure.Security.KeyVault.Secrets" Version="4.6.0" />
     <PackageReference Include="DnsClient" Version="1.7.0" />
+    <PackageReference Include="Microsoft.Bcl.HashCode" Version="6.0.0" />
+    <PackageReference Include="Microsoft.Extensions.Azure" Version="1.7.6" />
     <PackageReference Include="Microsoft.Extensions.DependencyInjection.Abstractions" Version="6.0.0" />
     <PackageReference Include="Microsoft.Extensions.Logging" Version="6.0.0" />
     <PackageReference Include="Microsoft.Extensions.Configuration" Version="6.0.1" />

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

@@ -1,6 +1,10 @@
 // Copyright (c) Microsoft Corporation.
 // Licensed under the MIT license.
 //
+using System;
+using System.Collections.Generic;
+using System.Linq;
+
 namespace Microsoft.Extensions.Configuration.AzureAppConfiguration.Models
 {
     /// <summary>
@@ -24,6 +28,11 @@ public class KeyValueSelector
         /// </summary>
         public string SnapshotName { get; set; }
 
+        /// <summary>
+        /// A filter that determines what tags to require when selecting key-values for the the configuration provider.
+        /// </summary>
+        public IEnumerable<string> TagFilters { get; set; }
+
         /// <summary>
         /// A boolean that signifies whether this selector is intended to select feature flags.
         /// </summary>
@@ -40,7 +49,11 @@ public override bool Equals(object obj)
             {
                 return KeyFilter == selector.KeyFilter
                     && LabelFilter == selector.LabelFilter
-                    && SnapshotName == selector.SnapshotName;
+                    && SnapshotName == selector.SnapshotName
+                    && (TagFilters == null
+                            ? selector.TagFilters == null
+                            : selector.TagFilters != null && new HashSet<string>(TagFilters).SetEquals(selector.TagFilters))
+                    && IsFeatureFlagSelector == selector.IsFeatureFlagSelector;
             }
 
             return false;
@@ -52,9 +65,22 @@ public override bool Equals(object obj)
         /// <returns>A hash code for the current object.</returns>
         public override int GetHashCode()
         {
-            return (KeyFilter?.GetHashCode() ?? 0) ^
-                   (LabelFilter?.GetHashCode() ?? 1) ^
-                   (SnapshotName?.GetHashCode() ?? 2);
+            string tagFiltersString = string.Empty;
+
+            if (TagFilters != null && TagFilters.Any())
+            {
+                var sortedTags = new SortedSet<string>(TagFilters);
+
+                // Concatenate tags into a single string with a delimiter
+                tagFiltersString = string.Join("\n", sortedTags);
+            }
+
+            return HashCode.Combine(
+                KeyFilter,
+                LabelFilter,
+                SnapshotName,
+                tagFiltersString,
+                IsFeatureFlagSelector);
         }
     }
 }

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

@@ -3,6 +3,7 @@
 //
 using Microsoft.Extensions.Configuration.AzureAppConfiguration.Extensions;
 using System;
+using System.Collections.Generic;
 
 namespace Microsoft.Extensions.Configuration.AzureAppConfiguration.Models
 {
@@ -18,6 +19,11 @@ internal class KeyValueWatcher
         /// </summary>
         public string Label { get; set; }
 
+        /// <summary>
+        /// Tags of the key-value to be watched.
+        /// </summary>
+        public IEnumerable<string> Tags { get; set; }
+
         /// <summary>
         /// A flag to refresh all key-values.
         /// </summary>

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

@@ -0,0 +1,16 @@
+// Copyright (c) Microsoft Corporation.
+// Licensed under the MIT license.
+//
+namespace Microsoft.Extensions.Configuration.AzureAppConfiguration
+{
+    /// <summary>
+    /// Defines well known tag values that are used within Azure App Configuration.
+    /// </summary>
+    public class TagValue
+    {
+        /// <summary>
+        /// Matches null tag values.
+        /// </summary>
+        public const string Null = "\0";
+    }
+}