From eb47c22339475490c2cba332e2d1892294e5612e Mon Sep 17 00:00:00 2001
From: Ilya <darpa@yandex.ru>
Date: Sat, 25 Jan 2020 14:10:39 +0500
Subject: [PATCH] Add custom 'Selected.*' type to PSCustomObject in
 Select-Object only once (#11548)

Before the fix Select-Object without parameters added custom 'Selected.' type to PSCustomObject even if this type was already present in TypeNames that was a memory leak in the edge case.
The cause of the problem was that Select-Object without parameters did not create a new object but forwarded the original.
The fix is to add custom 'Selected.' type only if object is original and it has not already custom 'Selected.*' type.
---
 .../commands/utility/Select-Object.cs         | 14 ++++++++----
 .../Select-Object.Tests.ps1                   | 22 +++++++++++++++++++
 2 files changed, 32 insertions(+), 4 deletions(-)

diff --git a/src/Microsoft.PowerShell.Commands.Utility/commands/utility/Select-Object.cs b/src/Microsoft.PowerShell.Commands.Utility/commands/utility/Select-Object.cs
index 8d97952d61..47a6c2d51c 100644
--- a/src/Microsoft.PowerShell.Commands.Utility/commands/utility/Select-Object.cs
+++ b/src/Microsoft.PowerShell.Commands.Utility/commands/utility/Select-Object.cs
@@ -607,7 +607,7 @@ namespace Microsoft.PowerShell.Commands
             {
                 if (obj != AutomationNull.Value)
                 {
-                    SetPSCustomObject(obj);
+                    SetPSCustomObject(obj, newPSObject: addedNoteProperties.Count > 0);
                     WriteObject(obj);
                 }
 
@@ -648,16 +648,22 @@ namespace Microsoft.PowerShell.Commands
 
                 if (isObjUnique)
                 {
-                    SetPSCustomObject(obj);
+                    SetPSCustomObject(obj, newPSObject: addedNoteProperties.Count > 0);
                     _uniques.Add(new UniquePSObjectHelper(obj, addedNoteProperties.Count));
                 }
             }
         }
 
-        private void SetPSCustomObject(PSObject psObj)
+        private void SetPSCustomObject(PSObject psObj, bool newPSObject)
         {
             if (psObj.ImmediateBaseObject is PSCustomObject)
-                psObj.TypeNames.Insert(0, "Selected." + InputObject.BaseObject.GetType().ToString());
+            {
+                var typeName = "Selected." + InputObject.BaseObject.GetType().ToString();
+                if (newPSObject || !psObj.TypeNames.Contains(typeName))
+                {
+                    psObj.TypeNames.Insert(0, typeName);
+                }
+            }
         }
 
         private void ProcessObjectAndHandleErrors(PSObject pso)
diff --git a/test/powershell/Modules/Microsoft.PowerShell.Utility/Select-Object.Tests.ps1 b/test/powershell/Modules/Microsoft.PowerShell.Utility/Select-Object.Tests.ps1
index e1de2303a4..2071e0a53c 100644
--- a/test/powershell/Modules/Microsoft.PowerShell.Utility/Select-Object.Tests.ps1
+++ b/test/powershell/Modules/Microsoft.PowerShell.Utility/Select-Object.Tests.ps1
@@ -1,5 +1,6 @@
 # Copyright (c) Microsoft Corporation. All rights reserved.
 # Licensed under the MIT License.
+
 . (Join-Path -Path $PSScriptRoot -ChildPath Test-Mocks.ps1)
 Add-TestDynamicType
 
@@ -349,4 +350,25 @@ Describe "Select-Object with Property = '*'" -Tags "CI" {
 		$p = Get-Process -Id $PID | Select-Object -Property Process* -ExcludeProperty ProcessorAffinity -ExpandProperty Modules
 		$p[0].psobject.Properties.Item("ProcessorAffinity") | Should -BeNullOrEmpty
     }
+
+    It "Select-Object add 'Selected.*' type only once" {
+        $obj = [PSCustomObject]@{ Name = 1 }
+
+        $obj.psobject.TypeNames.Count | Should -Be 2
+        $obj.psobject.TypeNames | Should -Not -BeLike "Selected*"
+
+        $obj = $obj | Select-Object
+
+        $obj.psobject.TypeNames.Count | Should -Be 3
+        $obj.psobject.TypeNames[0] | Should -BeLike "Selected*"
+        $obj.psobject.TypeNames[1] | Should -Not -BeLike "Selected*"
+        $obj.psobject.TypeNames[2] | Should -Not -BeLike "Selected*"
+
+        $obj = $obj | Select-Object
+
+        $obj.psobject.TypeNames.Count | Should -Be 3
+        $obj.psobject.TypeNames[0] | Should -BeLike "Selected*"
+        $obj.psobject.TypeNames[1] | Should -Not -BeLike "Selected*"
+        $obj.psobject.TypeNames[2] | Should -Not -BeLike "Selected*"
+    }
 }