Support getting task messages from a subfolder if present

src/StructuredLogger/Analyzers/CscTaskAnalyzer.cs

@@ -15,7 +15,7 @@ public static (Folder Analyzers, Folder Generators) Analyze(Task task)
             Folder currentReport = null;
             Folder parent = null;
 
-            foreach (var message in task.Children.OfType<Message>().ToArray())
+            foreach (var message in task.GetMessages().ToArray())
             {
                 var text = message.Text;
                 if (text.StartsWith(Strings.TotalAnalyzerExecutionTime, StringComparison.Ordinal))

src/StructuredLogger/ObjectModel/Task.cs

@@ -1,4 +1,7 @@
-namespace Microsoft.Build.Logging.StructuredLogger
+using System.Collections.Generic;
+using System.Linq;
+
+namespace Microsoft.Build.Logging.StructuredLogger
 {
     public class Task : TimedNode, IHasSourceFile, IHasLineNumber
     {
@@ -11,6 +14,17 @@ public class Task : TimedNode, IHasSourceFile, IHasLineNumber
         public virtual bool IsDerivedTask => this.GetType() != typeof(Task);
 
         public int? LineNumber { get; set; }
+
+        public IReadOnlyList<Message> GetMessages()
+        {
+            TreeNode node = this;
+            if (this.FindChild<Folder>(Strings.Messages) is Folder messagesFolder)
+            {
+                node = messagesFolder;
+            }
+
+            return node.Children.OfType<Message>().ToArray();
+        }
     }
 
     public class MSBuildTask : Task

src/StructuredLogger/ObjectModel/Tasks/CopyTask.cs

@@ -21,7 +21,7 @@ protected virtual IEnumerable<FileCopyOperation> GetFileCopyOperations()
             List<FileCopyOperation> list = new List<FileCopyOperation>();
 
             Match match;
-            foreach (var message in this.Children.OfType<Message>())
+            foreach (var message in this.GetMessages())
             {
                 var text = message.Text;
 

src/StructuredLogger/ObjectModel/Tasks/RobocopyTask.cs

@@ -18,7 +18,7 @@ protected override IEnumerable<FileCopyOperation> GetFileCopyOperations()
             List<FileCopyOperation> list = new List<FileCopyOperation>();
 
             Match match;
-            foreach (var message in Children.OfType<Message>())
+            foreach (var message in GetMessages())
             {
                 var text = message.Text;