From 673117cf612d920ff96852af34879fa19d1ba157 Mon Sep 17 00:00:00 2001
From: Michael Klement <mklement0@gmail.com>
Date: Sun, 26 Nov 2017 15:23:30 -0500
Subject: [PATCH] Fix accidental wrapping of scalar Write-Output input

when -NoEnumerate is used.

Fix #5122
---
 .../commands/utility/Write-Object.cs          | 24 +++++++++++++++++--
 .../Write-Output.Tests.ps1                    |  8 +++++++
 2 files changed, 30 insertions(+), 2 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 2ac76d2c63a..ae0274f472c 100644
--- a/src/Microsoft.PowerShell.Commands.Utility/commands/utility/Write-Object.cs
+++ b/src/Microsoft.PowerShell.Commands.Utility/commands/utility/Write-Object.cs
@@ -3,6 +3,7 @@
 --********************************************************************/
 
 using System.Management.Automation;
+using System.Collections.Generic;
 
 namespace Microsoft.PowerShell.Commands
 {
@@ -14,7 +15,7 @@ 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;
+        private object _inputObjects = null;
 
         /// <summary>
         /// Holds the list of objects to be Written
@@ -22,7 +23,7 @@ public sealed class WriteOutputCommand : PSCmdlet
         [Parameter(Position = 0, Mandatory = true, ValueFromPipeline = true, ValueFromRemainingArguments = true)]
         [AllowNull]
         [AllowEmptyCollection]
-        public PSObject[] InputObject
+        public object InputObject
         {
             get { return _inputObjects; }
             set { _inputObjects = value; }
@@ -39,6 +40,25 @@ public SwitchParameter NoEnumerate
             set;
         }
 
+        /// <summary>
+        /// This method implements the BeginProcessing method for Write-output command
+        /// </summary>
+        protected override void BeginProcessing() {
+            // If the input is a List<object> instance with a single element,
+            // assume that it is a single argument bound via ValueFromRemainingArguments and unwrap it.
+            // Note: 
+            //  * This case is indistinguishable from something like the following:
+            //      Write-Output -NoEnumerate -InputObject ([System.Collections.Generic.List[object]]::new((, 1)))
+            //    However, this seems like an acceptable price to pay in order to prevent unexpected wrapping of
+            //    a scalar in a collection when using -NoEnumerate.
+            //  * Is the case of *multiple* ValueFromRemainingArguments values, the List<object> instance
+            //    is passed through when -NoEnumerate is specified.
+            List<object> lst;
+            if (_inputObjects is List<object> && (lst = (List<object>)_inputObjects).Count == 1) {
+                _inputObjects = lst[0];
+            }            
+        }
+
         /// <summary>
         /// This method implements the ProcessRecord method for Write-output command
         /// </summary>
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 bca5d13a239..7899a8a9a54 100644
--- a/test/powershell/Modules/Microsoft.PowerShell.Utility/Write-Output.Tests.ps1
+++ b/test/powershell/Modules/Microsoft.PowerShell.Utility/Write-Output.Tests.ps1
@@ -71,4 +71,12 @@ Describe "Write-Output" -Tags "CI" {
 	    $singleCollection | Should Be 1
 	}
     }
+
+    Context "Scalar input" {
+        It "Write-Object -NoEnumerate should not wrap a scalar" {
+            Write-Output -NoEnumerate 1              | Should BeOfType [int]
+            Write-Output -NoEnumerate -InputObject 1 | Should BeOfType [int]
+            1 | Write-Output -NoEnumerate            | Should BeOfType [int]
+        }
+    }
 }