Fix ConsoleExporter fails silently when exporting an `ActivityLink` without Tags. (#3932)

src/OpenTelemetry.Exporter.Console/CHANGELOG.md

@@ -2,6 +2,10 @@
 
 ## Unreleased
 
+* Bug fix, ConsoleExporter fails silently when exporting an `ActivityLink`
+  without Tags.
+  ([#3932](https://github.com/open-telemetry/opentelemetry-dotnet/pull/3932))
+
 ## 1.4.0-beta.3
 
 Released 2022-Nov-07

src/OpenTelemetry.Exporter.Console/ConsoleActivityExporter.cs

@@ -115,7 +115,7 @@ namespace OpenTelemetry.Exporter
                     foreach (var activityLink in activity.Links)
                     {
                         this.WriteLine($"    {activityLink.Context.TraceId} {activityLink.Context.SpanId}");
-                        foreach (var attribute in activityLink.Tags)
+                        foreach (ref readonly var attribute in activityLink.EnumerateTagObjects())
                         {
                             if (ConsoleTagTransformer.Instance.TryTransformTag(attribute, out var result))
                             {

test/OpenTelemetry.Exporter.Console.Tests/ConsoleActivityExporterTest.cs

@@ -0,0 +1,61 @@
+// <copyright file="ConsoleActivityExporterTest.cs" company="OpenTelemetry Authors">
+// Copyright The OpenTelemetry Authors
+//
+// Licensed under the Apache License, Version 2.0 (the "License");
+// you may not use this file except in compliance with the License.
+// You may obtain a copy of the License at
+//
+//     http://www.apache.org/licenses/LICENSE-2.0
+//
+// Unless required by applicable law or agreed to in writing, software
+// distributed under the License is distributed on an "AS IS" BASIS,
+// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+// See the License for the specific language governing permissions and
+// limitations under the License.
+// </copyright>
+
+using System.Diagnostics;
+using OpenTelemetry.Tests;
+using OpenTelemetry.Trace;
+using Xunit;
+
+namespace OpenTelemetry.Exporter.Console.Tests;
+
+public class ConsoleActivityExporterTest
+{
+    [Fact]
+    public void VerifyConsoleActivityExporterDoesntFailWithoutActivityLinkTags()
+    {
+        var activitySourceName = Utils.GetCurrentMethodName();
+        using var activitySource = new ActivitySource(activitySourceName);
+
+        var exportedItems = new List<Activity>();
+
+        using var tracerProvider = Sdk.CreateTracerProviderBuilder()
+            .AddSource(activitySourceName)
+            .AddInMemoryExporter(exportedItems)
+            .Build();
+
+        ActivityContext context;
+        using (var first = activitySource.StartActivity("first"))
+        {
+            context = first!.Context;
+        }
+
+        exportedItems.Clear();
+
+        var links = new[] { new ActivityLink(context) };
+        using (var secondActivity = activitySource.StartActivity(ActivityKind.Internal, links: links, name: "Second"))
+        {
+        }
+
+        // Assert that an Activity was exported where ActivityLink.Tags == null.
+        var activity = exportedItems[0];
+        Assert.Equal("Second", activity.DisplayName);
+        Assert.Null(activity.Links.First().Tags);
+
+        // Test that the ConsoleExporter correctly handles an Activity without Tags.
+        using var consoleExporter = new ConsoleActivityExporter(new ConsoleExporterOptions());
+        Assert.Equal(ExportResult.Success, consoleExporter.Export(new Batch<Activity>(new[] { activity }, 1)));
+    }
+}

test/OpenTelemetry.Exporter.Console.Tests/OpenTelemetry.Exporter.Console.Tests.csproj

@@ -19,6 +19,9 @@
 
   <ItemGroup>
     <ProjectReference Include="$(RepoRoot)\src\OpenTelemetry.Exporter.Console\OpenTelemetry.Exporter.Console.csproj" />
+    <ProjectReference Include="$(RepoRoot)\src\OpenTelemetry.Exporter.InMemory\OpenTelemetry.Exporter.InMemory.csproj" />
+
+    <Compile Include="$(RepoRoot)\test\OpenTelemetry.Tests\Shared\Utils.cs" Link="Includes\Utils.cs" />
   </ItemGroup>
 
 </Project>

test/OpenTelemetry.Tests/Shared/Utils.cs

@@ -25,7 +25,11 @@ namespace OpenTelemetry.Tests
         public static string GetCurrentMethodName()
         {
             var method = new StackFrame(1).GetMethod();
-            return $"{method.DeclaringType.FullName}.{method.Name}";
+
+            Debug.Assert(method != null, "Failed to get Method from the executing stack.");
+            Debug.Assert(method!.DeclaringType != null, "DeclaringType is not expected to be null.");
+
+            return $"{method.DeclaringType!.FullName}.{method.Name}";
         }
     }
 }