Powershell: Write-Output -NoEnumerate outputs PSObject[] rather than Object[] and generally doesn't respect the input collection type

[mklement0]

^{Related: #5122}

• Write-Output -NoEnumerate, when given a collection, always returns a PSObject[] rather than a regular object[]] array, which is unexpected.

• Additionally, this means that if a different collection type such as [System.Collections.ArrayList] was passed, it is _not_ preserved.

  • Write-Output's documentation, which currently only states, "prevents Write-Output from enumerating output", which sounds like the input collection - whatever its type - is simply _passed through_ - a sensible expectation that _Windows PowerShell_ versions up to v5.1 indeed honor.

I suspect this regression is a consequence of the ill-fated #2038 PR that arose out of issue #2035.

Steps to reproduce

(Write-Output -NoEnumerate 1, 2).GetType().Name
(Write-Output -NoEnumerate ([System.Collections.ArrayList] (1, 2))).GetType().Name

Expected behavior

Object[]
ArrayList

This is how it still works in _Windows PowerShell_ v5.1

Actual behavior

PSObject[]
PSObject[]

As stated, this affects PS _Core_ only.

Environment data

PowerShell Core v6.0.0 on macOS 10.13.2
PowerShell Core v6.0.0 on Ubuntu 16.04.3 LTS
PowerShell Core v6.0.0 on Microsoft Windows 10 Pro (64-bit; v10.0.15063)

[iSazonov]

If it is a regression - it is a bug.

[Jaykul]

How has this been allowed to continue for this long?

[vexx32]

@Jaykul Fixing this now. After a longer-than-necessary foray into the pipeline files, it turns out that typing your parameters as PSObject[] forces PS to enumerate whatever collection you throw at it during the parameter binding stage. Typing the param as PSObject works for both singletons and collections just fine, though.