Powershell: Unable to remove (default) property of registry item

[ZSkycat]

Steps to reproduce

New-Item 'registry::HKEY_CURRENT_USER\test'
Set-ItemProperty 'registry::HKEY_CURRENT_USER\test' -Name '(default)' -Value 'test1'
Remove-ItemProperty 'registry::HKEY_CURRENT_USER\test' -Name '(default)'

Remove-ItemProperty : Property (default) does not exist at path HKEY_CURRENT_USER\test.
At line:1 char:1
+ Remove-ItemProperty 'registry::HKEY_CURRENT_USER\test' -Name '(defaul ...
+ ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
+ CategoryInfo          : InvalidArgument: ((default):String) [Remove-ItemProperty], PSArgumentException
+ FullyQualifiedErrorId : System.Management.Automation.PSArgumentException,Microsoft.PowerShell.Commands.RemoveItemPropertyCommand

see more https://github.com/PSAppDeployToolkit/PSAppDeployToolkit/issues/146

Expected behavior

Actual behavior

Environment data

> $PSVersionTable
Name                           Value
----                           -----
PSVersion                      6.0.1
PSEdition                      Core
GitCommitId                    v6.0.1
OS                             Microsoft Windows 10.0.16299
Platform                       Win32NT
PSCompatibleVersions           {1.0, 2.0, 3.0, 4.0...}
PSRemotingProtocolVersion      2.3
SerializationVersion           1.1.0.1
WSManStackVersion              3.0

[iSazonov]

@ZSkycat Could you please repo with latest PowerShell Core build?

[ZSkycat]

@iSazonov 6.0.1 reproduce this bug

[stknohg]

Related this, I found very strange behavior.

I add "(default)" property in this registry key.

# set default(no named) property
New-Item 'registry::HKEY_CURRENT_USER\test'
Set-ItemProperty 'registry::HKEY_CURRENT_USER\test' -Name '(default)' -Value 'test1'

# add "(default)" property
$regkey = [Microsoft.Win32.Registry]::CurrentUser.OpenSubKey("test", $true)
$regKey.SetValue('(default)','test2')
$regkey.Close()

After commands, HKEY_CURRENT_USER\test has 2 properties.

1. Default(no named) : value is "test1"
2. "(default)" : value is "test2"

In this condition, Remove-ItemProperty -Name '(default)' exits without error and default(no named) property value has deleted.

# no error
Remove-ItemProperty 'registry::HKEY_CURRENT_USER\test' -Name '(default)'

---

The cause of this behavior is below,

https://github.com/PowerShell/PowerShell/blob/67c9ae47f81a38ee3fcc1e16b187b79fb9cbe148/src/System.Management.Automation/namespaces/RegistryProvider.cs#L2329-L2333

Registry provider changes the property name("(default)" to "") just before deleting value not at validating property name.

[iSazonov]

I believe it is bug - default value name should be null.

[ZSkycat]

@iSazonov
I found a way to get (default). It is an empty string.

New-Item 'registry::HKEY_CURRENT_USER\test' -Value 'i am test'
$a = Get-Item 'registry::HKEY_CURRENT_USER\test'
$a.GetValue('')

but, SetValue is not working

$a.SetValue('', 'i am test1')
# Exception calling "SetValue" with "2" argument(s): "Cannot write to the registry key."
# At line:1 char:1
# + $a.SetValue('', 'i am test1')
# + ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
# + CategoryInfo          : NotSpecified: (:) [], MethodInvocationException
# + FullyQualifiedErrorId : UnauthorizedAccessException

$a.SetValue('', 'i am test1', [Microsoft.Win32.RegistryValueKind]::String)
# Exception calling "SetValue" with "3" argument(s): "Cannot write to the registry key."
# At line:1 char:1
# + $a.SetValue('', 'i am test1', [Microsoft.Win32.RegistryValueKind]::St ...
# + ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
# + CategoryInfo          : NotSpecified: (:) [], MethodInvocationException
# + FullyQualifiedErrorId : UnauthorizedAccessException

and Set-Item can working

Set-Item 'registry::HKEY_CURRENT_USER\test' -Value 'i am test'

---

https://github.com/PowerShell/PowerShell/blob/67c9ae47f81a38ee3fcc1e16b187b79fb9cbe148/src/System.Management.Automation/namespaces/RegistryProvider.cs#L216-L230

I know why it can not work. Because it does not have write permission.
QAQ
I still use Microsoft.Win32.Registry to solve the problem.

[iSazonov]

@ZSkycat Thanks for your research - feel free to create PR.