From 18d5037ad2a97db7b306171a4ba4be0dcce91e5e Mon Sep 17 00:00:00 2001
From: "Joel Sallow (/u/ta11ow)" <32407840+vexx32@users.noreply.github.com>
Date: Wed, 13 Mar 2019 04:54:12 -0400
Subject: [PATCH] Fix -NoEnumerate behaviour in Write-Output (#9069)

Fix is to preserve input collection type in output.
The regression was caused by #2038
---
 .../commands/utility/Write-Object.cs          | 29 ++-----
 .../Write-Output.Tests.ps1                    | 76 +++++++++++--------
 2 files changed, 49 insertions(+), 56 deletions(-)

diff --git a/src/Microsoft.PowerShell.Commands.Utility/commands/utility/Write-Object.cs b/src/Microsoft.PowerShell.Commands.Utility/commands/utility/Write-Object.cs
index f0cd5d4b2..376f30f51 100644
--- a/src/Microsoft.PowerShell.Commands.Utility/commands/utility/Write-Object.cs
+++ b/src/Microsoft.PowerShell.Commands.Utility/commands/utility/Write-Object.cs
@@ -12,49 +12,32 @@ namespace Microsoft.PowerShell.Commands
     [Cmdlet(VerbsCommunications.Write, "Output", HelpUri = "https://go.microsoft.com/fwlink/?LinkID=113427", RemotingCapability = RemotingCapability.None)]
     public sealed class WriteOutputCommand : PSCmdlet
     {
-        private PSObject[] _inputObjects = null;
-
         /// <summary>
         /// Holds the list of objects to be written.
         /// </summary>
         [Parameter(Position = 0, Mandatory = true, ValueFromPipeline = true, ValueFromRemainingArguments = true)]
         [AllowNull]
         [AllowEmptyCollection]
-        public PSObject[] InputObject
-        {
-            get { return _inputObjects; }
-
-            set { _inputObjects = value; }
-        }
+        public PSObject InputObject { get; set; }
 
         /// <summary>
         /// Prevents Write-Output from unravelling collections passed to the InputObject parameter.
         /// </summary>
-        [Parameter()]
-        public SwitchParameter NoEnumerate
-        {
-            get;
-            set;
-        }
+        [Parameter]
+        public SwitchParameter NoEnumerate { get; set; }
 
         /// <summary>
         /// This method implements the ProcessRecord method for Write-output command.
         /// </summary>
         protected override void ProcessRecord()
         {
-            if (_inputObjects == null)
+            if (InputObject == null)
             {
-                WriteObject(_inputObjects);
+                WriteObject(InputObject);
                 return;
             }
 
-            bool enumerate = true;
-            if (NoEnumerate.IsPresent)
-            {
-                enumerate = false;
-            }
-
-            WriteObject(_inputObjects, enumerate);
+            WriteObject(InputObject, !NoEnumerate.IsPresent);
         }
     }
     #endregion
diff --git a/test/powershell/Modules/Microsoft.PowerShell.Utility/Write-Output.Tests.ps1 b/test/powershell/Modules/Microsoft.PowerShell.Utility/Write-Output.Tests.ps1
index 648913ecd..08cc880a0 100644
--- a/test/powershell/Modules/Microsoft.PowerShell.Utility/Write-Output.Tests.ps1
+++ b/test/powershell/Modules/Microsoft.PowerShell.Utility/Write-Output.Tests.ps1
@@ -18,60 +18,70 @@ Describe "Write-Output DRT Unit Tests" -Tags "CI" {
 
     It "Works with NoEnumerate switch" {
         $objectWritten = 1, 2.2, @("John", "Smith", 10), "abc"
-        [string]$s = Write-Output $objectWritten -NoEnumerate 6>&1 
+        [string]$s = Write-Output $objectWritten -NoEnumerate 6>&1
         $s | Should -Be  '1 2.2 System.Object[] abc'
     }
+
+    It "Preserves the input collection type and contents with -NoEnumerate" {
+        $List = [System.Collections.Generic.List[string]]::new( [string[]]@("test", "one", "two") )
+        $ObjectWritten = Write-Output $List -NoEnumerate
+
+        $ObjectWritten.GetType() | Should -Be ([System.Collections.Generic.List[string]])
+        $ObjectWritten[0] | Should -BeExactly "test"
+        $ObjectWritten[1] | Should -BeExactly "one"
+        $ObjectWritten[2] | Should -BeExactly "two"
+    }
 }
 
 Describe "Write-Output" -Tags "CI" {
     $testString = $testString
     Context "Input Tests" {
-	It "Should allow piped input" {
-	    { $testString | Write-Output } | Should -Not -Throw
-	}
+        It "Should allow piped input" {
+            { $testString | Write-Output } | Should -Not -Throw
+        }
 
-	It "Should write output to the output stream when using piped input" {
-	    $testString | Write-Output | Should -Be $testString
-	}
+        It "Should write output to the output stream when using piped input" {
+            $testString | Write-Output | Should -Be $testString
+        }
 
-	It "Should use inputobject switch" {
-	    { Write-Output -InputObject $testString } | Should -Not -Throw
-	}
+        It "Should use inputobject switch" {
+            { Write-Output -InputObject $testString } | Should -Not -Throw
+        }
 
-	It "Should write output to the output stream when using inputobject switch" {
-	    Write-Output -InputObject $testString | Should -Be $testString
-	}
+        It "Should write output to the output stream when using inputobject switch" {
+            Write-Output -InputObject $testString | Should -Be $testString
+        }
 
-	It "Should be able to write to a variable" {
-	    Write-Output -InputObject $testString -OutVariable var
-	    $var | Should -Be $testString
-	}
+        It "Should be able to write to a variable" {
+            Write-Output -InputObject $testString -OutVariable var
+            $var | Should -Be $testString
+        }
     }
 
     Context "Pipeline Command Tests" {
-	It "Should send object to the next command in the pipeline" {
-	    Write-Output -InputObject (1+1) | Should -Be 2
-	}
+        It "Should send object to the next command in the pipeline" {
+            Write-Output -InputObject (1 + 1) | Should -Be 2
+        }
 
-	It "Should have the same result between inputobject switch and piped input" {
-	    Write-Output -InputObject (1+1) | Should -Be 2
+        It "Should have the same result between inputobject switch and piped input" {
+            Write-Output -InputObject (1 + 1) | Should -Be 2
 
-	    1+1 | Write-Output | Should -Be 2
-	}
+            1 + 1 | Write-Output | Should -Be 2
+        }
     }
 
     Context "Enumerate Objects" {
-	$enumerationObject = @(1,2,3)
-	It "Should see individual objects when not using the NoEnumerate switch" {
-	    $singleCollection = $(Write-Output $enumerationObject| Measure-Object).Count
+        $enumerationObject = @(1, 2, 3)
+        It "Should see individual objects when not using the NoEnumerate switch" {
+            $singleCollection = $(Write-Output $enumerationObject| Measure-Object).Count
 
-	    $singleCollection | Should -Be $enumerationObject.length
-	}
+            $singleCollection | Should -Be $enumerationObject.length
+        }
 
-	It "Should be able to treat a collection as a single object using the NoEnumerate switch" {
-	    $singleCollection = $(Write-Output $enumerationObject -NoEnumerate | Measure-Object).Count
+        It "Should be able to treat a collection as a single object using the NoEnumerate switch" {
+            $singleCollection = $(Write-Output $enumerationObject -NoEnumerate | Measure-Object).Count
 
-	    $singleCollection | Should -Be 1
-	}
+            $singleCollection | Should -Be 1
+        }
     }
 }