From 326071c3078d75a5fb36558ea17115687b5debd7 Mon Sep 17 00:00:00 2001
From: Eric Arndt <erarndt@microsoft.com>
Date: Wed, 7 May 2025 15:17:10 -0700
Subject: [PATCH 1/2] Reduce allocations in TaskExecutionHost

---
 .../TaskExecutionHost/TaskExecutionHost.cs    | 23 ++++++++++++++++---
 1 file changed, 20 insertions(+), 3 deletions(-)

diff --git a/src/Build/BackEnd/TaskExecutionHost/TaskExecutionHost.cs b/src/Build/BackEnd/TaskExecutionHost/TaskExecutionHost.cs
index 2f5a26be1fc..a168d42e635 100644
--- a/src/Build/BackEnd/TaskExecutionHost/TaskExecutionHost.cs
+++ b/src/Build/BackEnd/TaskExecutionHost/TaskExecutionHost.cs
@@ -24,6 +24,7 @@
 
 using TaskItem = Microsoft.Build.Execution.ProjectItemInstance.TaskItem;
 using Task = System.Threading.Tasks.Task;
+using Microsoft.Build.Collections;
 
 #nullable disable
 
@@ -1423,11 +1424,27 @@ private void GatherTaskItemOutputs(bool outputTargetIsItem, string outputTargetN
 
                                     static IEnumerable<KeyValuePair<string, string>> EnumerateMetadata(IDictionary customMetadata)
                                     {
-                                        foreach (DictionaryEntry de in customMetadata)
+                                        if (customMetadata is CopyOnWriteDictionary<string> copyOnWriteDictionary)
                                         {
-                                            yield return new KeyValuePair<string, string>((string)de.Key, EscapingUtilities.Escape((string)de.Value));
+                                            foreach (KeyValuePair<string, string> kvp in copyOnWriteDictionary)
+                                            {
+                                                yield return new KeyValuePair<string, string>(kvp.Key, EscapingUtilities.Escape(kvp.Value));
+                                            }
+                                        }
+                                        else if (customMetadata is Dictionary<string, string> dictionary)
+                                        {
+                                            foreach (KeyValuePair<string, string> kvp in dictionary)
+                                            {
+                                                yield return new KeyValuePair<string, string>(kvp.Key, EscapingUtilities.Escape(kvp.Value));
+                                            }
+                                        }
+                                        else
+                                        {
+                                            foreach (DictionaryEntry de in customMetadata)
+                                            {
+                                                yield return new KeyValuePair<string, string>((string)de.Key, EscapingUtilities.Escape((string)de.Value));
+                                            }
                                         }
-                                    }
                                 }
                             }
 

From cf381f3905189ccb3da2e388616ba21950931af3 Mon Sep 17 00:00:00 2001
From: Tomas Bartonek <tom.bartonek@volny.cz>
Date: Fri, 9 May 2025 14:29:56 +0200
Subject: [PATCH 2/2] Update TaskExecutionHost.cs

I think this parenthesis was deleted by error.
If it was a different one, more thorough look will be needed
---
 src/Build/BackEnd/TaskExecutionHost/TaskExecutionHost.cs | 1 +
 1 file changed, 1 insertion(+)

diff --git a/src/Build/BackEnd/TaskExecutionHost/TaskExecutionHost.cs b/src/Build/BackEnd/TaskExecutionHost/TaskExecutionHost.cs
index a168d42e635..9523e2ea4ca 100644
--- a/src/Build/BackEnd/TaskExecutionHost/TaskExecutionHost.cs
+++ b/src/Build/BackEnd/TaskExecutionHost/TaskExecutionHost.cs
@@ -1445,6 +1445,7 @@ static IEnumerable<KeyValuePair<string, string>> EnumerateMetadata(IDictionary c
                                                 yield return new KeyValuePair<string, string>((string)de.Key, EscapingUtilities.Escape((string)de.Value));
                                             }
                                         }
+                                    }
                                 }
                             }