Write-Output $null -NoEnumerate produces different Collection<PSObject> in 5.1 vs 6.0

[alx9r]

I'm not sure which behavior is better, but I expected 5.1 and 6.0 to behave the same in this respect. If this change is deliberate I would like to understand why.

Steps to reproduce

$r = [System.Collections.ObjectModel.Collection[psobject]]{Write-Output $null -NoEnumerate}.Invoke()
$r.item(0).GetType()

Behavior in PowerShell 5.1

You cannot call a method on a null-valued expression.
At C:\Users\un1\Desktop\test.ps1:2 char:1
+ $r[0].GetType()
+ ~~~~~~~~~~~~~~~
    + CategoryInfo          : InvalidOperation: (:) [], RuntimeException
    + FullyQualifiedErrorId : InvokeMethodOnNull

>$PSVersionTable

Name                           Value                                                                    
----                           -----                                                                    
PSVersion                      5.1.14409.1012                                                           
PSEdition                      Desktop                                                                  
PSCompatibleVersions           {1.0, 2.0, 3.0, 4.0...}                                                  
BuildVersion                   10.0.14409.1012                                                          
CLRVersion                     4.0.30319.42000                                                          
WSManStackVersion              3.0                                                                      
PSRemotingProtocolVersion      2.3                                                                      
SerializationVersion           1.1.0.1                                                                  

Behavior in PowerShell 6.0

IsPublic IsSerial Name                                     BaseType
-------- -------- ----                                     --------
True     True     PSObject[]                               System.Array

> $PSVersionTable

Name                           Value                                            
----                           -----                                            
PSVersion                      6.0.2                                            
PSEdition                      Core                                             
GitCommitId                    v6.0.2                                           
OS                             Microsoft Windows 6.3.9600                       
Platform                       Win32NT                                          
PSCompatibleVersions           {1.0, 2.0, 3.0, 4.0...}                          
PSRemotingProtocolVersion      2.3                                              
SerializationVersion           1.1.0.1                                          
WSManStackVersion              3.0                                                                                        

[mklement0]

Indeed, Write-Output is broken - see #5955 and #5122, and it all seems to be the result of the ill-fated #2038 PR that arose out of issue #2035.

[alx9r]

Oi. That's a messy broken business, indeed.

[alx9r]

It looks like this change to Write-Output is the culprit. Copying the command from the revision prior and renaming to Write-Output2 seems to result in behavior consistent with PowerShell 5.1:

Add-Type '
    using System.Management.Automation;

    [Cmdlet(VerbsCommunications.Write, "Output2")]
    public class WriteOutput2Command : PSCmdlet
    {
        private PSObject[] _inputObjects = null;

        [Parameter(Position = 0, Mandatory = true, ValueFromPipeline = true, ValueFromRemainingArguments = true)]
        [AllowNull]
        [AllowEmptyCollection]
        public PSObject[] InputObject
        {
            get { return _inputObjects; }
            set { _inputObjects = value; }
        }

        [Parameter()]
        public SwitchParameter NoEnumerate
        {
            get;
            set;
        }

        protected override void ProcessRecord()
        {
            if (null == _inputObjects)
            {
                WriteObject(_inputObjects);
                return;
            }

            bool enumerate = true;
            if (NoEnumerate.IsPresent)
            {
                enumerate = false;
            }
            foreach (PSObject inputObject in _inputObjects)
            {
                WriteObject(inputObject, enumerate);
            }
        }//processrecord
    }' -PassThru | % Assembly | Import-Module

$r = [System.Collections.ObjectModel.Collection[psobject]]{Write-Output2 $Null -NoEnumerate}.Invoke()
$r.Item(0).GetType()

outputs

You cannot call a method on a null-valued expression.
At C:\users\un1\Desktop\test2.ps1:46 char:1
+ $r.Item(0).GetType()
+ ~~~~~~~~~~~~~~~~~~~~
    + CategoryInfo          : InvalidOperation: (:) [], RuntimeException
    + FullyQualifiedErrorId : InvokeMethodOnNull

[microsoft-github-policy-service]

This issue has not had any activity in 6 months, if this is a bug please try to reproduce on the latest version of PowerShell and reopen a new issue and reference this issue if this is still a blocker for you.

[microsoft-github-policy-service]

This issue has not had any activity in 6 months, if this is a bug please try to reproduce on the latest version of PowerShell and reopen a new issue and reference this issue if this is still a blocker for you.

[microsoft-github-policy-service]

This issue has not had any activity in 6 months, if this is a bug please try to reproduce on the latest version of PowerShell and reopen a new issue and reference this issue if this is still a blocker for you.

[microsoft-github-policy-service]

This issue has been marked as "No Activity" as there has been no activity for 6 months. It has been closed for housekeeping purposes.