[draft] Trim ActivitySource via System.Diagnostics.ActivitySource.IsSupported feature

src/libraries/System.Diagnostics.DiagnosticSource/src/ILLink/ILLink.Substitutions.Shared.xml

@@ -4,4 +4,9 @@
       <method signature="System.Boolean get_Enabled()" body="stub" value="false" />
     </type>
   </assembly>
+  <assembly fullname="System.Diagnostics.DiagnosticSource" feature="System.Diagnostics.ActivitySource.IsSupported" featurevalue="false">
+    <type fullname="System.Diagnostics.ActivitySource">
+      <method signature="System.Boolean HasListeners()" body="stub" value="false" />
+    </type>
+  </assembly>
 </linker>

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

@@ -55,13 +55,11 @@ internal ActivityChangedEventArgs(Activity? previous, Activity? current)
     /// </summary>
     public partial class Activity : IDisposable
     {
-#pragma warning disable CA1825 // Array.Empty<T>() doesn't exist in all configurations
-        private static readonly IEnumerable<KeyValuePair<string, string?>> s_emptyBaggageTags = new KeyValuePair<string, string?>[0];
-        private static readonly IEnumerable<KeyValuePair<string, object?>> s_emptyTagObjects = new KeyValuePair<string, object?>[0];
-        private static readonly IEnumerable<ActivityLink> s_emptyLinks = new DiagLinkedList<ActivityLink>();
-        private static readonly IEnumerable<ActivityEvent> s_emptyEvents = new DiagLinkedList<ActivityEvent>();
-#pragma warning restore CA1825
-        private static readonly ActivitySource s_defaultSource = new ActivitySource(string.Empty);
+        private static readonly IEnumerable<KeyValuePair<string, string?>> s_emptyBaggageTags = [];
+        private static readonly IEnumerable<KeyValuePair<string, object?>> s_emptyTagObjects = [];
+        private static readonly IEnumerable<ActivityLink> s_emptyLinks = [];
+        private static readonly IEnumerable<ActivityEvent> s_emptyEvents = [];
+        private static readonly ActivitySource? s_defaultSource = ActivitySource.IsSupported ? new ActivitySource(string.Empty) : null;
         private static readonly AsyncLocal<Activity?> s_current = new AsyncLocal<Activity?>();
 
         private const byte ActivityTraceFlagsIsSet = 0b_1_0000000; // Internal flag to indicate if flags have been set
@@ -453,7 +451,14 @@ public IEnumerable<ActivityLink> Links
         /// <param name="operationName">Operation's name <see cref="OperationName"/></param>
         public Activity(string operationName)
         {
-            Source = s_defaultSource;
+            if (!ActivitySource.IsSupported)
+            {
+                throw new NotSupportedException("Linked away");
+            }
+            else
+            {
+                Source = s_defaultSource!;
+            }
             // Allow data by default in the constructor to keep the compatibility.
             IsAllDataRequested = true;
 
@@ -485,6 +490,11 @@ public Activity(string operationName)
         /// <param name="value">The tag value mapped to the input key</param>
         public Activity AddTag(string key, object? value)
         {
+            if (!ActivitySource.IsSupported)
+            {
+                throw new NotSupportedException("Linked away");
+            }
+
             KeyValuePair<string, object?> kvp = new KeyValuePair<string, object?>(key, value);
 
             if (_tags != null || Interlocked.CompareExchange(ref _tags, new TagsLinkedList(kvp), null) != null)
@@ -509,6 +519,11 @@ public Activity AddTag(string key, object? value)
         /// <returns><see langword="this" /> for convenient chaining.</returns>
         public Activity SetTag(string key, object? value)
         {
+            if (!ActivitySource.IsSupported)
+            {
+                throw new NotSupportedException("Linked away");
+            }
+
             KeyValuePair<string, object?> kvp = new KeyValuePair<string, object?>(key, value);
 
             if (_tags != null || Interlocked.CompareExchange(ref _tags, new TagsLinkedList(kvp, set: true), null) != null)
@@ -526,6 +541,11 @@ public Activity SetTag(string key, object? value)
         /// <returns><see langword="this" /> for convenient chaining.</returns>
         public Activity AddEvent(ActivityEvent e)
         {
+            if (!ActivitySource.IsSupported)
+            {
+                throw new NotSupportedException("Linked away");
+            }
+
             if (_events != null || Interlocked.CompareExchange(ref _events, new DiagLinkedList<ActivityEvent>(e), null) != null)
             {
                 _events.Add(e);
@@ -551,8 +571,11 @@ public Activity AddEvent(ActivityEvent e)
         /// </remarks>
         public Activity AddException(Exception exception, in TagList tags = default, DateTimeOffset timestamp = default)
         {
+            if (!ActivitySource.IsSupported)
+            {
+                throw new NotSupportedException("Linked away");
+            }
             ArgumentNullException.ThrowIfNull(exception);
-
             TagList exceptionTags = tags;
 
             Source.NotifyActivityAddException(this, exception, ref exceptionTags);
@@ -611,6 +634,11 @@ public Activity AddException(Exception exception, in TagList tags = default, Dat
         /// </remarks>
         public Activity AddLink(ActivityLink link)
         {
+            if (!ActivitySource.IsSupported)
+            {
+                throw new NotSupportedException("Linked away");
+            }
+
             if (_links != null || Interlocked.CompareExchange(ref _links, new DiagLinkedList<ActivityLink>(link), null) != null)
             {
                 _links.Add(link);
@@ -630,6 +658,11 @@ public Activity AddLink(ActivityLink link)
         /// <returns><see langword="this" /> for convenient chaining.</returns>
         public Activity AddBaggage(string key, string? value)
         {
+            if (!ActivitySource.IsSupported)
+            {
+                throw new NotSupportedException("Linked away");
+            }
+
             KeyValuePair<string, string?> kvp = new KeyValuePair<string, string?>(key, value);
 
             if (_baggage != null || Interlocked.CompareExchange(ref _baggage, new BaggageLinkedList(kvp), null) != null)
@@ -654,6 +687,11 @@ public Activity AddBaggage(string key, string? value)
         /// <returns><see langword="this" /> for convenient chaining.</returns>
         public Activity SetBaggage(string key, string? value)
         {
+            if (!ActivitySource.IsSupported)
+            {
+                throw new NotSupportedException("Linked away");
+            }
+
             KeyValuePair<string, string?> kvp = new KeyValuePair<string, string?>(key, value);
 
             if (_baggage != null || Interlocked.CompareExchange(ref _baggage, new BaggageLinkedList(kvp, set: true), null) != null)
@@ -675,6 +713,11 @@ public Activity SetBaggage(string key, string? value)
         /// <param name="parentId">The id of the parent operation.</param>
         public Activity SetParentId(string parentId)
         {
+            if (!ActivitySource.IsSupported)
+            {
+                throw new NotSupportedException("Linked away");
+            }
+
             if (_id != null || _spanId != null)
             {
                 // Cannot set the parent on already started Activity.
@@ -705,6 +748,11 @@ public Activity SetParentId(string parentId)
         /// </summary>
         public Activity SetParentId(ActivityTraceId traceId, ActivitySpanId spanId, ActivityTraceFlags activityTraceFlags = ActivityTraceFlags.None)
         {
+            if (!ActivitySource.IsSupported)
+            {
+                throw new NotSupportedException("Linked away");
+            }
+
             if (_id != null || _spanId != null)
             {
                 // Cannot set the parent on already started Activity.
@@ -735,6 +783,11 @@ public Activity SetParentId(ActivityTraceId traceId, ActivitySpanId spanId, Acti
         /// <returns><see langword="this" /> for convenient chaining.</returns>
         public Activity SetStartTime(DateTime startTimeUtc)
         {
+            if (!ActivitySource.IsSupported)
+            {
+                throw new NotSupportedException("Linked away");
+            }
+
             if (startTimeUtc.Kind != DateTimeKind.Utc)
             {
                 NotifyError(new InvalidOperationException(SR.StartTimeNotUtc));
@@ -755,6 +808,11 @@ public Activity SetStartTime(DateTime startTimeUtc)
         /// <returns><see langword="this" /> for convenient chaining.</returns>
         public Activity SetEndTime(DateTime endTimeUtc)
         {
+            if (!ActivitySource.IsSupported)
+            {
+                throw new NotSupportedException("Linked away");
+            }
+
             if (endTimeUtc.Kind != DateTimeKind.Utc)
             {
                 NotifyError(new InvalidOperationException(SR.EndTimeNotUtc));
@@ -788,6 +846,11 @@ public Activity SetEndTime(DateTime endTimeUtc)
         /// <seealso cref="SetStartTime(DateTime)"/>
         public Activity Start()
         {
+            if (!ActivitySource.IsSupported)
+            {
+                throw new NotSupportedException("Linked away");
+            }
+
             // Has the ID already been set (have we called Start()).
             if (_id != null || _spanId != null)
             {
@@ -844,6 +907,11 @@ public Activity Start()
         /// <seealso cref="SetEndTime(DateTime)"/>
         public void Stop()
         {
+            if (!ActivitySource.IsSupported)
+            {
+                throw new NotSupportedException("Linked away");
+            }
+
             if (_id == null && _spanId == null)
             {
                 NotifyError(new InvalidOperationException(SR.ActivityNotStarted));
@@ -1176,6 +1244,10 @@ internal static Activity Create(ActivitySource source, string name, ActivityKind
                                         IEnumerable<KeyValuePair<string, object?>>? tags, IEnumerable<ActivityLink>? links, DateTimeOffset startTime,
                                         ActivityTagsCollection? samplerTags, ActivitySamplingResult request, bool startIt, ActivityIdFormat idFormat, string? traceState)
         {
+            if (!ActivitySource.IsSupported)
+            {
+                throw new NotSupportedException("Linked away");
+            }
             Activity activity = new Activity(name);
 
             activity.Source = source;

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

@@ -3,6 +3,8 @@
 
 using System.Collections.Generic;
 using System.ComponentModel;
+using System.Diagnostics.CodeAnalysis;
+using System.Diagnostics.Metrics;
 using System.Runtime.CompilerServices;
 using System.Threading;
 
@@ -14,6 +16,10 @@ public sealed class ActivitySource : IDisposable
         private static readonly SynchronizedList<ActivityListener> s_allListeners = new SynchronizedList<ActivityListener>();
         private SynchronizedList<ActivityListener>? _listeners;
 
+        [FeatureSwitchDefinition("System.Diagnostics.ActivitySource.IsSupported")]
+        internal static bool IsSupported { get; } = InitializeIsActivitySourceSupported();
+        private static bool InitializeIsActivitySourceSupported() => AppContext.TryGetSwitch("System.Diagnostics.ActivitySource.IsSupported", out bool isSupported) ? isSupported : true;
+
         /// <summary>
         /// Construct an ActivitySource object with the input name
         /// </summary>
@@ -47,6 +53,10 @@ private ActivitySource(string name, string? version, IEnumerable<KeyValuePair<st
             Name = name ?? throw new ArgumentNullException(nameof(name));
             Version = version;
             TelemetrySchemaUrl = telemetrySchemaUrl;
+            if (!IsSupported)
+            {
+                return;
+            }
 
             // Sorting the tags to make sure the tags are always in the same order.
             // Sorting can help in comparing the tags used for any scenario.
@@ -71,8 +81,10 @@ private ActivitySource(string name, string? version, IEnumerable<KeyValuePair<st
                     }
                 }
             }, this);
-
-            GC.KeepAlive(DiagnosticSourceEventSource.Log);
+            if (Meter.IsEventSourceSupported)
+            {
+                GC.KeepAlive(DiagnosticSourceEventSource.Log);
+            }
         }
 
         /// <summary>
@@ -103,6 +115,10 @@ private ActivitySource(string name, string? version, IEnumerable<KeyValuePair<st
         /// </summary>
         public bool HasListeners()
         {
+            if (!IsSupported)
+            {
+                return false;
+            }
             SynchronizedList<ActivityListener>? listeners = _listeners;
             return listeners != null && listeners.Count > 0;
         }
@@ -203,6 +219,10 @@ public bool HasListeners()
         private Activity? CreateActivity(string name, ActivityKind kind, ActivityContext context, string? parentId, IEnumerable<KeyValuePair<string, object?>>? tags,
                                             IEnumerable<ActivityLink>? links, DateTimeOffset startTime, bool startIt = true, ActivityIdFormat idFormat = ActivityIdFormat.Unknown)
         {
+            if (!IsSupported)
+            {
+                return null;
+            }
             // _listeners can get assigned to null in Dispose.
             SynchronizedList<ActivityListener>? listeners = _listeners;
             if (listeners == null || listeners.Count == 0)
@@ -336,8 +356,11 @@ public bool HasListeners()
         /// </summary>
         public void Dispose()
         {
-            _listeners = null;
-            s_activeSources.Remove(this);
+            if (IsSupported)
+            {
+                _listeners = null;
+                s_activeSources.Remove(this);
+            }
         }
 
         /// <summary>
@@ -348,7 +371,7 @@ public static void AddActivityListener(ActivityListener listener)
         {
             ArgumentNullException.ThrowIfNull(listener);
 
-            if (s_allListeners.AddIfNotExist(listener))
+            if (IsSupported && s_allListeners.AddIfNotExist(listener))
             {
                 s_activeSources.EnumWithAction((source, obj) => {
                     var shouldListenTo = ((ActivityListener)obj).ShouldListenTo;
@@ -364,6 +387,10 @@ public static void AddActivityListener(ActivityListener listener)
 
         internal void AddListener(ActivityListener listener)
         {
+            if (!IsSupported)
+            {
+                return;
+            }
             if (_listeners == null)
             {
                 Interlocked.CompareExchange(ref _listeners, new SynchronizedList<ActivityListener>(), null);
@@ -374,12 +401,20 @@ internal void AddListener(ActivityListener listener)
 
         internal static void DetachListener(ActivityListener listener)
         {
+            if (!IsSupported)
+            {
+                return;
+            }
             s_allListeners.Remove(listener);
             s_activeSources.EnumWithAction((source, obj) => source._listeners?.Remove((ActivityListener) obj), listener);
         }
 
         internal void NotifyActivityStart(Activity activity)
         {
+            if (!IsSupported)
+            {
+                return;
+            }
             Debug.Assert(activity != null);
 
             // _listeners can get assigned to null in Dispose.
@@ -392,6 +427,10 @@ internal void NotifyActivityStart(Activity activity)
 
         internal void NotifyActivityStop(Activity activity)
         {
+            if (!IsSupported)
+            {
+                return;
+            }
             Debug.Assert(activity != null);
 
             // _listeners can get assigned to null in Dispose.
@@ -404,6 +443,10 @@ internal void NotifyActivityStop(Activity activity)
 
         internal void NotifyActivityAddException(Activity activity, Exception exception, ref TagList tags)
         {
+            if (!IsSupported)
+            {
+                return;
+            }
             Debug.Assert(activity != null);
 
             // _listeners can get assigned to null in Dispose.

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

@@ -3,6 +3,7 @@
 
 using System.Collections.Generic;
 using System.Diagnostics.CodeAnalysis;
+using System.Diagnostics.Metrics;
 using System.Threading;
 
 namespace System.Diagnostics
@@ -144,7 +145,10 @@ public DiagnosticListener(string name)
 
             // Touch DiagnosticSourceEventSource.Logger so we ensure that the
             // DiagnosticSourceEventSource has been constructed (and thus is responsive to ETW requests to be enabled).
-            GC.KeepAlive(DiagnosticSourceEventSource.Log);
+            if (Meter.IsEventSourceSupported)
+            {
+                GC.KeepAlive(DiagnosticSourceEventSource.Log);
+            }
         }
 
         /// <summary>

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

@@ -20,6 +20,11 @@ public static DsesActivitySourceListener Create(
         DiagnosticSourceEventSource eventSource,
         DsesFilterAndTransform activitySourceSpecs)
     {
+        if (!ActivitySource.IsSupported)
+        {
+            throw new NotSupportedException("Linked away");
+        }
+
         var listener = new DsesActivitySourceListener(eventSource);
 
         listener.NormalizeActivitySourceSpecsList(activitySourceSpecs);