Add DebuggerDisplay and DebuggerTypeProxy to Activity and related types (#121054)

---------

Co-authored-by: copilot-swe-agent[bot] <[email protected]>
Co-authored-by: stephentoub <[email protected]>
Co-authored-by: tarekgh <[email protected]>

Author: 3 people

src/libraries/System.Diagnostics.DiagnosticSource/src/System/Diagnostics/Activity.cs

@@ -54,6 +54,8 @@ internal ActivityChangedEventArgs(Activity? previous, Activity? current)
     /// but the exception is suppressed, and the operation does something reasonable (typically
     /// doing nothing).
     /// </summary>
+    [DebuggerDisplay("{DebuggerDisplayString,nq}")]
+    [DebuggerTypeProxy(typeof(ActivityDebuggerProxy))]
     public partial class Activity : IDisposable
     {
 #pragma warning disable CA1825 // Array.Empty<T>() doesn't exist in all configurations
@@ -1839,6 +1841,15 @@ public override string ToString()
             }
         }
 
+        private string DebuggerDisplayString
+        {
+            get
+            {
+                string? id = Id;
+                return $"OperationName = {OperationName}, Id = {(id is not null ? id : "(null)")}";
+            }
+        }
+
         [Flags]
         private enum State : byte
         {
@@ -2168,4 +2179,30 @@ public void CopyTo(Span<byte> destination)
             ActivityTraceId.SetSpanFromHexChars(ToHexString().AsSpan(), destination);
         }
     }
+
+    internal sealed class ActivityDebuggerProxy(Activity activity)
+    {
+        public ActivityTraceFlags ActivityTraceFlags => activity.ActivityTraceFlags;
+        public List<KeyValuePair<string, string?>> Baggage => new List<KeyValuePair<string, string?>>(activity.Baggage);
+        public ActivityContext Context => activity.Context;
+        public string DisplayName => activity.DisplayName;
+        public TimeSpan Duration => activity.Duration;
+        public List<ActivityEvent> Events => new List<ActivityEvent>(activity.Events);
+        public bool HasRemoteParent => activity.HasRemoteParent;
+        public string? Id => activity.Id;
+        public ActivityKind Kind => activity.Kind;
+        public List<ActivityLink> Links => new List<ActivityLink>(activity.Links);
+        public string OperationName => activity.OperationName;
+        public Activity? Parent => activity.Parent;
+        public string? ParentId => activity.ParentId;
+        public ActivitySpanId ParentSpanId => activity.ParentSpanId;
+        public ActivitySource Source => activity.Source;
+        public ActivitySpanId SpanId => activity.SpanId;
+        public DateTime StartTimeUtc => activity.StartTimeUtc;
+        public ActivityStatusCode Status => activity.Status;
+        public string? StatusDescription => activity.StatusDescription;
+        public List<KeyValuePair<string, object?>> TagObjects => new List<KeyValuePair<string, object?>>(activity.TagObjects);
+        public ActivityTraceId TraceId => activity.TraceId;
+        public string? TraceStateString => activity.TraceStateString;
+    }
 }

src/libraries/System.Diagnostics.DiagnosticSource/src/System/Diagnostics/ActivityContext.cs

@@ -10,6 +10,7 @@ namespace System.Diagnostics
     /// ActivityContext representation conforms to the w3c TraceContext specification. It contains two identifiers
     /// a TraceId and a SpanId - along with a set of common TraceFlags and system-specific TraceState values.
     /// </summary>
+    [DebuggerDisplay("TraceId = {TraceId}, SpanId = {SpanId}, TraceFlags = {TraceFlags}")]
     public readonly partial struct ActivityContext : IEquatable<ActivityContext>
     {
         /// <summary>

src/libraries/System.Diagnostics.DiagnosticSource/src/System/Diagnostics/ActivityEvent.cs

@@ -9,6 +9,7 @@ namespace System.Diagnostics
     /// <summary>
     /// A text annotation associated with a collection of tags.
     /// </summary>
+    [DebuggerDisplay("Name = {Name}, Timestamp = {Timestamp}")]
     public readonly struct ActivityEvent
     {
         private static readonly IEnumerable<KeyValuePair<string, object?>> s_emptyTags = Array.Empty<KeyValuePair<string, object?>>();

src/libraries/System.Diagnostics.DiagnosticSource/src/System/Diagnostics/ActivityLink.cs

@@ -12,6 +12,7 @@ namespace System.Diagnostics
     /// Links can be used to represent batched operations where a Activity was initiated by multiple initiating Activities,
     /// each representing a single incoming item being processed in the batch.
     /// </summary>
+    [DebuggerDisplay("{DebuggerDisplayString,nq}")]
     public readonly partial struct ActivityLink : IEquatable<ActivityLink>
     {
         private readonly Activity.TagsLinkedList? _tags;
@@ -38,6 +39,8 @@ public ActivityLink(ActivityContext context, ActivityTagsCollection? tags = null
         /// </summary>
         public IEnumerable<KeyValuePair<string, object?>>? Tags => _tags;
 
+        private string DebuggerDisplayString => $"TraceId = {Context.TraceId}, SpanId = {Context.SpanId}";
+
         public override bool Equals([NotNullWhen(true)] object? obj) => (obj is ActivityLink link) && this.Equals(link);
 
         public bool Equals(ActivityLink value) => Context == value.Context && value.Tags == Tags;

src/libraries/System.Diagnostics.DiagnosticSource/src/System/Diagnostics/ActivitySource.cs

@@ -8,6 +8,7 @@
 
 namespace System.Diagnostics
 {
+    [DebuggerDisplay("Name = {Name}")]
     public sealed class ActivitySource : IDisposable
     {
         private static readonly SynchronizedList<ActivitySource> s_activeSources = new SynchronizedList<ActivitySource>();

src/libraries/System.Diagnostics.DiagnosticSource/tests/ActivityTests.cs

@@ -2548,5 +2548,65 @@ public void OnError(Exception error) { }
         }
 
         private const int MaxClockErrorMSec = 20;
+
+        [Fact]
+        public void TestActivityDebuggerDisplay()
+        {
+            Activity activity = new Activity("TestOperation");
+            activity.Start();
+
+            string debuggerDisplay = DebuggerAttributes.ValidateDebuggerDisplayReferences(activity);
+            Assert.Contains("OperationName = TestOperation", debuggerDisplay);
+            Assert.Contains("Id =", debuggerDisplay);
+
+            activity.Stop();
+        }
+
+        [Fact]
+        public void TestActivityDebuggerProxy()
+        {
+            Activity activity = new Activity("TestOperation");
+            activity.SetTag("key1", "value1");
+            activity.SetTag("key2", 42);
+            activity.SetBaggage("baggage1", "baggageValue1");
+            activity.AddEvent(new ActivityEvent("TestEvent"));
+            activity.Start();
+
+            DebuggerAttributes.ValidateDebuggerTypeProxyProperties(activity);
+
+            activity.Stop();
+        }
+
+        [Fact]
+        public void TestActivityContextDebuggerDisplay()
+        {
+            ActivityTraceId traceId = ActivityTraceId.CreateRandom();
+            ActivitySpanId spanId = ActivitySpanId.CreateRandom();
+            ActivityContext context = new ActivityContext(traceId, spanId, ActivityTraceFlags.Recorded);
+
+            string debuggerDisplay = DebuggerAttributes.ValidateDebuggerDisplayReferences(context);
+            Assert.NotNull(debuggerDisplay);
+        }
+
+        [Fact]
+        public void TestActivityLinkDebuggerDisplay()
+        {
+            ActivityTraceId traceId = ActivityTraceId.CreateRandom();
+            ActivitySpanId spanId = ActivitySpanId.CreateRandom();
+            ActivityContext context = new ActivityContext(traceId, spanId, ActivityTraceFlags.Recorded);
+            ActivityLink link = new ActivityLink(context);
+
+            DebuggerAttributes.ValidateDebuggerDisplayReferences(link);
+        }
+
+        [Fact]
+        public void TestActivityEventDebuggerDisplay()
+        {
+            ActivityEvent activityEvent = new ActivityEvent("TestEvent");
+
+            string debuggerDisplay = DebuggerAttributes.ValidateDebuggerDisplayReferences(activityEvent);
+            Assert.Contains("Name = \"TestEvent\"", debuggerDisplay);
+            Assert.Contains("Timestamp =", debuggerDisplay);
+        }
     }
 }

src/libraries/System.Diagnostics.DiagnosticSource/tests/System.Diagnostics.DiagnosticSource.Tests.csproj

@@ -23,6 +23,7 @@
   </ItemGroup>
 
   <ItemGroup>
+    <Compile Include="$(CommonTestPath)System\Diagnostics\DebuggerAttributes.cs" Link="Common\System\Diagnostics\DebuggerAttributes.cs" />
     <Compile Include="..\src\System\Diagnostics\DsesSamplerBuilder.cs" Link="DsesSamplerBuilder.cs" />
     <Compile Include="..\src\System\Diagnostics\RateLimiter.cs" Link="RateLimiter.cs" />
     <Compile Include="..\src\System\Diagnostics\Helpers.cs" Link="Helpers.cs" />