Idea for immutability for TestNode + PropertyBag

src/Platform/Microsoft.Testing.Platform/Messages/PropertyBag.cs

@@ -23,102 +23,14 @@ public sealed partial class PropertyBag
     internal /* for testing */ Property? _property;
 #pragma warning restore SA1401 // Fields should be private
 
-    public PropertyBag()
-    {
-    }
-
-    public PropertyBag(params IProperty[] properties)
+    internal PropertyBag(IEnumerable<IProperty> properties, TestNodeStateProperty testNodeStateProperty)
     {
         ArgumentGuard.IsNotNull(properties);
+        ArgumentGuard.IsNotNull(testNodeStateProperty);
 
-        if (properties.Length == 0)
-        {
-            return;
-        }
-
-        for (int i = 0; i < properties.Length; i++)
-        {
-            if (properties[i] is TestNodeStateProperty testNodeStateProperty)
-            {
-                if (_testNodeStateProperty is not null)
-                {
-                    ThrowDuplicatedPropertyType(properties[i]);
-                }
-
-                _testNodeStateProperty = testNodeStateProperty;
-            }
-            else
-            {
-                if (_property is null)
-                {
-                    _property = new(properties[i]);
-                }
-                else
-                {
-                    if (_property.Contains(properties[i]))
-                    {
-                        ThrowDuplicatedPropertyInstance(properties[i]);
-                    }
-
-                    _property = new(properties[i], _property);
-                }
-            }
-        }
-    }
-
-    public PropertyBag(IEnumerable<IProperty> properties)
-    {
-        ArgumentGuard.IsNotNull(properties);
+        _testNodeStateProperty = testNodeStateProperty;
 
         foreach (IProperty property in properties)
-        {
-            if (property is TestNodeStateProperty testNodeStateProperty)
-            {
-                if (_testNodeStateProperty is not null)
-                {
-                    ThrowDuplicatedPropertyType(property);
-                }
-
-                _testNodeStateProperty = testNodeStateProperty;
-            }
-            else
-            {
-                if (_property is null)
-                {
-                    _property = new(property);
-                }
-                else
-                {
-                    if (_property.Contains(property))
-                    {
-                        ThrowDuplicatedPropertyInstance(property);
-                    }
-
-                    _property = new(property, _property);
-                }
-            }
-        }
-    }
-
-    public int Count => _property is null
-        ? _testNodeStateProperty is null ? 0 : 1
-        : _property.Count + (_testNodeStateProperty is not null ? 1 : 0);
-
-    public void Add(IProperty property)
-    {
-        ArgumentGuard.IsNotNull(property);
-
-        // Optimized access to the TestNodeStateProperty, it's one of the most used property.
-        if (property is TestNodeStateProperty testNodeStateProperty)
-        {
-            if (_testNodeStateProperty is not null)
-            {
-                ThrowDuplicatedPropertyType(property);
-            }
-
-            _testNodeStateProperty = testNodeStateProperty;
-        }
-        else
         {
             if (_property is null)
             {
@@ -136,6 +48,10 @@ public void Add(IProperty property)
         }
     }
 
+    public int Count => _property is null
+        ? _testNodeStateProperty is null ? 0 : 1
+        : _property.Count + (_testNodeStateProperty is not null ? 1 : 0);
+
     public bool Any<TProperty>()
         where TProperty : IProperty
     {

src/Platform/Microsoft.Testing.Platform/Messages/PropertyBagBuilder.cs

@@ -0,0 +1,20 @@
+// Copyright (c) Microsoft Corporation. All rights reserved.
+// Licensed under the MIT license. See LICENSE file in the project root for full license information.
+
+namespace Microsoft.Testing.Platform.Extensions.Messages;
+
+public class PropertyBagBuilder : List<IProperty>
+{
+    public new PropertyBagBuilder Add(IProperty property)
+    {
+        base.Add(property);
+        return this;
+    }
+
+    public PropertyBag ToImmutablePropertyBag(TestNodeStateProperty currentState)
+    {
+        IEnumerable<IProperty> nonTestStateProperties = this.Where(x => x is not TestNodeStateProperty);
+
+        return new PropertyBag(nonTestStateProperties, currentState);
+    }
+}

src/Platform/Microsoft.Testing.Platform/Messages/TestNode.cs

@@ -7,11 +7,18 @@ namespace Microsoft.Testing.Platform.Extensions.Messages;
 
 public class TestNode
 {
-    public required TestNodeUid Uid { get; init; }
+    internal TestNode(TestNodeUid uid, string displayName, PropertyBag properties)
+    {
+        Uid = uid;
+        DisplayName = displayName;
+        Properties = properties;
+    }
+
+    public TestNodeUid Uid { get; }
 
-    public required string DisplayName { get; init; }
+    public string DisplayName { get; }
 
-    public PropertyBag Properties { get; init; } = new();
+    public PropertyBag Properties { get; }
 
     public override string ToString()
     {

src/Platform/Microsoft.Testing.Platform/Messages/TestNodeBuilder.cs

@@ -0,0 +1,22 @@
+// Copyright (c) Microsoft Corporation. All rights reserved.
+// Licensed under the MIT license. See LICENSE file in the project root for full license information.
+
+namespace Microsoft.Testing.Platform.Extensions.Messages;
+
+public class TestNodeBuilder
+{
+    public required TestNodeUid Uid { get; init; }
+
+    public required string DisplayName { get; init; }
+
+    public PropertyBagBuilder Properties { get; init; } = new();
+
+    public TestNodeBuilder WithProperty(IProperty property)
+    {
+        Properties.Add(property);
+        return this;
+    }
+
+    public TestNode ToImmutableTestNode(TestNodeStateProperty currentState) =>
+        new(Uid, DisplayName, Properties.ToImmutablePropertyBag(currentState));
+}