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Fix accidental wrapping of scalar Write-Output input #5552

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Fix accidental wrapping of scalar Write-Output input #5552

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24 changes: 22 additions & 2 deletions src/Microsoft.PowerShell.Commands.Utility/commands/utility/Write-Object.cs
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Original file line number Diff line number Diff line change
Expand Up @@ -3,6 +3,7 @@
--********************************************************************/

using System.Management.Automation;
using System.Collections.Generic;

namespace Microsoft.PowerShell.Commands
{
Expand All @@ -14,15 +15,15 @@ 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
/// </summary>
[Parameter(Position = 0, Mandatory = true, ValueFromPipeline = true, ValueFromRemainingArguments = true)]
[AllowNull]
[AllowEmptyCollection]
public PSObject[] InputObject
public object InputObject
{
get { return _inputObjects; }
set { _inputObjects = value; }
Expand All @@ -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>
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8 changes: 8 additions & 0 deletions test/powershell/Modules/Microsoft.PowerShell.Utility/Write-Output.Tests.ps1
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Expand Up @@ -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]
}
}
}