Idea for how we might recognize a default collection in freezable options types

eng/Packages.Data.props

@@ -103,6 +103,7 @@
     <PackageReference Update="System.ValueTuple" Version="4.5.0" />
     <PackageReference Update="Microsoft.Bcl.AsyncInterfaces" Version="6.0.0" />
     <PackageReference Update="Microsoft.CSharp" Version="4.7.0" />
+		<PackageReference Update="Microsoft.Extensions.Logging.Abstractions" Version="6.0.0"/>
 
     <!-- Azure SDK packages -->
     <PackageReference Update="Azure.Communication.Identity" Version="1.3.1" />

sdk/core/System.ClientModel/api/System.ClientModel.net6.0.cs

@@ -95,6 +95,14 @@ public void Send(System.ClientModel.Primitives.PipelineMessage message) { }
     public partial class ClientPipelineOptions
     {
         public ClientPipelineOptions() { }
+        public System.Collections.Generic.IList<string> AllowedHeaderNames { get { throw null; } }
+        public System.Collections.Generic.IList<string> AllowedQueryParameters { get { throw null; } }
+        public bool? EnableLogging { get { throw null; } set { } }
+        public bool? EnableMessageContentLogging { get { throw null; } set { } }
+        public bool? EnableMessageLogging { get { throw null; } set { } }
+        public Microsoft.Extensions.Logging.ILoggerFactory? LoggerFactory { get { throw null; } set { } }
+        public int? MessageContentSizeLimit { get { throw null; } set { } }
+        public System.ClientModel.Primitives.PipelinePolicy? MessageLoggingPolicy { get { throw null; } set { } }
         public System.TimeSpan? NetworkTimeout { get { throw null; } set { } }
         public System.ClientModel.Primitives.PipelinePolicy? RetryPolicy { get { throw null; } set { } }
         public System.ClientModel.Primitives.PipelineTransport? Transport { get { throw null; } set { } }
@@ -158,6 +166,13 @@ public JsonModelConverter(System.ClientModel.Primitives.ModelReaderWriterOptions
         public override System.ClientModel.Primitives.IJsonModel<object> Read(ref System.Text.Json.Utf8JsonReader reader, System.Type typeToConvert, System.Text.Json.JsonSerializerOptions options) { throw null; }
         public override void Write(System.Text.Json.Utf8JsonWriter writer, System.ClientModel.Primitives.IJsonModel<object> value, System.Text.Json.JsonSerializerOptions options) { }
     }
+    public partial class MessageLoggingPolicy : System.ClientModel.Primitives.PipelinePolicy
+    {
+        public MessageLoggingPolicy(System.ClientModel.Primitives.ClientPipelineOptions? options = null) { }
+        public static System.ClientModel.Primitives.MessageLoggingPolicy Default { get { throw null; } }
+        public override void Process(System.ClientModel.Primitives.PipelineMessage message, System.Collections.Generic.IReadOnlyList<System.ClientModel.Primitives.PipelinePolicy> pipeline, int currentIndex) { }
+        public override System.Threading.Tasks.ValueTask ProcessAsync(System.ClientModel.Primitives.PipelineMessage message, System.Collections.Generic.IReadOnlyList<System.ClientModel.Primitives.PipelinePolicy> pipeline, int currentIndex) { throw null; }
+    }
     public static partial class ModelReaderWriter
     {
         public static object? Read(System.BinaryData data, [System.Diagnostics.CodeAnalysis.DynamicallyAccessedMembersAttribute(System.Diagnostics.CodeAnalysis.DynamicallyAccessedMemberTypes.NonPublicConstructors | System.Diagnostics.CodeAnalysis.DynamicallyAccessedMemberTypes.PublicConstructors)] System.Type returnType, System.ClientModel.Primitives.ModelReaderWriterOptions? options = null) { throw null; }

sdk/core/System.ClientModel/api/System.ClientModel.netstandard2.0.cs

@@ -95,6 +95,14 @@ public void Send(System.ClientModel.Primitives.PipelineMessage message) { }
     public partial class ClientPipelineOptions
     {
         public ClientPipelineOptions() { }
+        public System.Collections.Generic.IList<string> AllowedHeaderNames { get { throw null; } }
+        public System.Collections.Generic.IList<string> AllowedQueryParameters { get { throw null; } }
+        public bool? EnableLogging { get { throw null; } set { } }
+        public bool? EnableMessageContentLogging { get { throw null; } set { } }
+        public bool? EnableMessageLogging { get { throw null; } set { } }
+        public Microsoft.Extensions.Logging.ILoggerFactory? LoggerFactory { get { throw null; } set { } }
+        public int? MessageContentSizeLimit { get { throw null; } set { } }
+        public System.ClientModel.Primitives.PipelinePolicy? MessageLoggingPolicy { get { throw null; } set { } }
         public System.TimeSpan? NetworkTimeout { get { throw null; } set { } }
         public System.ClientModel.Primitives.PipelinePolicy? RetryPolicy { get { throw null; } set { } }
         public System.ClientModel.Primitives.PipelineTransport? Transport { get { throw null; } set { } }
@@ -157,6 +165,13 @@ public JsonModelConverter(System.ClientModel.Primitives.ModelReaderWriterOptions
         public override System.ClientModel.Primitives.IJsonModel<object> Read(ref System.Text.Json.Utf8JsonReader reader, System.Type typeToConvert, System.Text.Json.JsonSerializerOptions options) { throw null; }
         public override void Write(System.Text.Json.Utf8JsonWriter writer, System.ClientModel.Primitives.IJsonModel<object> value, System.Text.Json.JsonSerializerOptions options) { }
     }
+    public partial class MessageLoggingPolicy : System.ClientModel.Primitives.PipelinePolicy
+    {
+        public MessageLoggingPolicy(System.ClientModel.Primitives.ClientPipelineOptions? options = null) { }
+        public static System.ClientModel.Primitives.MessageLoggingPolicy Default { get { throw null; } }
+        public override void Process(System.ClientModel.Primitives.PipelineMessage message, System.Collections.Generic.IReadOnlyList<System.ClientModel.Primitives.PipelinePolicy> pipeline, int currentIndex) { }
+        public override System.Threading.Tasks.ValueTask ProcessAsync(System.ClientModel.Primitives.PipelineMessage message, System.Collections.Generic.IReadOnlyList<System.ClientModel.Primitives.PipelinePolicy> pipeline, int currentIndex) { throw null; }
+    }
     public static partial class ModelReaderWriter
     {
         public static object? Read(System.BinaryData data, System.Type returnType, System.ClientModel.Primitives.ModelReaderWriterOptions? options = null) { throw null; }

sdk/core/System.ClientModel/src/Internal/ChangeTrackingStringList.cs

@@ -0,0 +1,108 @@
+// Copyright (c) Microsoft Corporation. All rights reserved.
+// Licensed under the MIT License.
+
+using System.Collections;
+using System.Collections.Generic;
+using System.Collections.ObjectModel;
+
+namespace System.ClientModel.Internal;
+
+internal class ChangeTrackingStringList : IList<string>
+{
+    private IList<string> _list;
+
+    private bool _tracking;
+
+    public ChangeTrackingStringList()
+    {
+        _list = new List<string>();
+
+        _tracking = false;
+    }
+
+    public ChangeTrackingStringList(IEnumerable<string> collection)
+    {
+        _list = new List<string>(collection);
+
+        _tracking = false;
+    }
+
+    public bool HasChanged { get; private set; }
+
+    public void StartTracking() => _tracking = true;
+
+    public void StopTracking() => _tracking = false;
+
+    public void Freeze()
+    {
+        _list = new ReadOnlyCollection<string>(_list);
+    }
+
+    #region IList implementation
+
+    public string this[int index]
+    {
+        get => _list[index];
+        set
+        {
+            _list[index] = value;
+
+            HasChanged |= _tracking;
+        }
+    }
+
+    public int Count => _list.Count;
+
+    public bool IsReadOnly => _list.IsReadOnly;
+
+    public void Add(string item)
+    {
+        _list.Add(item);
+
+        HasChanged |= _tracking;
+    }
+
+    public void Clear()
+    {
+        int count = _list.Count;
+
+        _list.Clear();
+
+        HasChanged |= _tracking && (count != 0);
+    }
+
+    public bool Contains(string item) => _list.Contains(item);
+
+    public void CopyTo(string[] array, int arrayIndex) => _list.CopyTo(array, arrayIndex);
+
+    public IEnumerator<string> GetEnumerator() => _list.GetEnumerator();
+
+    public int IndexOf(string item) => _list.IndexOf(item);
+
+    public void Insert(int index, string item)
+    {
+        _list.Insert(index, item);
+
+        HasChanged |= _tracking;
+    }
+
+    public bool Remove(string item)
+    {
+        bool removed = _list.Remove(item);
+
+        HasChanged |= _tracking && removed;
+
+        return removed;
+    }
+
+    public void RemoveAt(int index)
+    {
+        _list.RemoveAt(index);
+
+        HasChanged |= _tracking;
+    }
+
+    IEnumerator IEnumerable.GetEnumerator() => GetEnumerator();
+
+    #endregion
+}

sdk/core/System.ClientModel/src/Internal/ContentTypeUtilities.cs

@@ -0,0 +1,54 @@
+// Copyright (c) Microsoft Corporation. All rights reserved.
+// Licensed under the MIT License.
+
+using System.Text;
+
+namespace System.ClientModel.Internal;
+
+internal class ContentTypeUtilities
+{
+    public static bool TryGetTextEncoding(string contentType, out Encoding? encoding)
+    {
+        const string charsetMarker = "; charset=";
+        const string utf8Charset = "utf-8";
+        const string textContentTypePrefix = "text/";
+        const string jsonSuffix = "json";
+        const string appJsonPrefix = "application/json";
+        const string xmlSuffix = "xml";
+        const string urlEncodedSuffix = "-urlencoded";
+
+        // Default is technically US-ASCII, but will default to UTF-8 which is a superset.
+        const string appFormUrlEncoded = "application/x-www-form-urlencoded";
+
+        if (contentType == null)
+        {
+            encoding = null;
+            return false;
+        }
+
+        var charsetIndex = contentType.IndexOf(charsetMarker, StringComparison.OrdinalIgnoreCase);
+        if (charsetIndex != -1)
+        {
+            ReadOnlySpan<char> charset = contentType.AsSpan().Slice(charsetIndex + charsetMarker.Length);
+            if (charset.StartsWith(utf8Charset.AsSpan(), StringComparison.OrdinalIgnoreCase))
+            {
+                encoding = Encoding.UTF8;
+                return true;
+            }
+        }
+
+        if (contentType.StartsWith(textContentTypePrefix, StringComparison.OrdinalIgnoreCase) ||
+            contentType.EndsWith(jsonSuffix, StringComparison.OrdinalIgnoreCase) ||
+            contentType.EndsWith(xmlSuffix, StringComparison.OrdinalIgnoreCase) ||
+            contentType.EndsWith(urlEncodedSuffix, StringComparison.OrdinalIgnoreCase) ||
+            contentType.StartsWith(appJsonPrefix, StringComparison.OrdinalIgnoreCase) ||
+            contentType.StartsWith(appFormUrlEncoded, StringComparison.OrdinalIgnoreCase))
+        {
+            encoding = Encoding.UTF8;
+            return true;
+        }
+
+        encoding = null;
+        return false;
+    }
+}