Unable to pipe Get-DbaUser into Remove-DbaUser when multiple users are selected on the same database

[OsirisDBA]

Before submitting a bug report:

• Ensure you are able to reproduce it on the latest released version (we release often)
• Verified this bug is not already reported in an issue
• Verified errors are not related to permissions
• Can reproduce in a clean PowerShell session (clean = powershell -NoProfile)

Steps to Reproduce

CREATE USER USER01 WITHOUT LOGIN;
CREATE USER USER02 WITHOUT LOGIN;

#Returns 2 users
get-dbadbuser -SqlInstance SQLSRV01 -Database DB01| Where-Object{ $_.Name -match "^USER(.*)" } | select Name

# Removes 1 user then errors
get-dbadbuser -SqlInstance SQLSRV01 -Database DB01| Where-Object{ $_.Name -match "^USER(.*)" } | Remove-DbaUser

#Workaround
get-dbadbuser -SqlInstance SQLSRV01 -Database DB01| Where-Object{ $_.Name -match "^USER(.*)" } | %{Remove-DbaUser -SqlInstance $_.SqlInstance -Database $_.Database -User $_.Name }

Expected Behavior

Both users should be removed

Actual Behavior

Single user is removed.

An error occurred while enumerating through a collection: Collection was modified; enumeration operation may not execute..
At line:36361 char:17
+                 $users | ForEach-Object {
+                 ~~~~~~~~~~~~~~~~~~~~~~~~~
    + CategoryInfo          : InvalidOperation: (Microsoft.SqlSe...dListEnumerator:SmoSortedListEnumerator) [], RuntimeException
    + FullyQualifiedErrorId : BadEnumeration

Environmental data

PowerShell:

Name                           Value
----                           -----
PSVersion                      5.1.14393.2636
PSEdition                      Desktop
PSCompatibleVersions           {1.0, 2.0, 3.0, 4.0...}
BuildVersion                   10.0.14393.2636
CLRVersion                     4.0.30319.42000
WSManStackVersion              3.0
PSRemotingProtocolVersion      2.3
SerializationVersion           1.1.0.1

SQL Server:

Microsoft SQL Server 2014 (SP2-CU13) (KB4456287) - 12.0.5590.1 (X64) Aug 1 2018 01:23:36 Copyright (c) Microsoft Corporation Enterprise Edition: Core-based Licensing (64-bit) on Windows NT 6.3 (Build 9600: ) (Hypervisor)

[sqllensman]

This issue here is that InputObject is being modified in the Pipeline
The example given can be made to work by either using.

$User = get-dbadbuser -SqlInstance SQLSRV01 -Database DB01| Where-Object{ $_.Name -match "^USER(.*)" }

$User | Remove-DbaUser

or

(get-dbadbuser -SqlInstance SQLSRV01 -Database DB01| Where-Object{ $_.Name -match "^USER(.*)" }) | Remove-DbaUser

[stale]

This issue has been automatically marked as stale because it has not had recent activity. If you would like this issue to remain open:

• Verify that you can still reproduce the issue in the latest version of dbatools
• Comment that the issue is still reproducible and include:
  • What version of dbatools you reproduced the issue on
  • What OS and version you reproduced the issue on
  • What steps you followed to reproduce the issue

[potatoqualitee]

This may help enumeration issues that we face. Perhaps we can generically wrap it.

https://twitter.com/Lee_Holmes/status/1105896696142155776