Mocking a function with OrderedDictionary parameter throws error with PowerShell 7, runs fine with PowerShell 5

[MartinusVastenhouw]

Checklist

• Issue has a meaningful title
• I have searched the existing issues. See all issues
• I have tested using the latest version of Pester. See Installation and update guide.

What is the issue?

Mocking a function that has a parameter of type [System.Collections.Specialized.OrderedDictionary] throws an error when using PowerShell 7 (version 7.3.4) but runs fine when using PowerShell 5.
See test script in attached file (hehe.txt).
hehe.txt

Expected Behavior

Pester should not throw an error. If it works in PowerShell 5 it should also work in PowerShell 7.

Steps To Reproduce

Running below tests in PowerShell 7 throws an error. They run fine with PowerShell 5.

Describe 'Difference between PowerShell 7 and PowerShell 5' {
    BeforeAll {
        function Test-WithOrderedDictionary {
            [CmdletBinding()]
            param (
                [Parameter(Mandatory = $true)]
                [System.Collections.Specialized.OrderedDictionary]
                $Context
            )

            Write-Information -MessageData "INFO -- Test-WithOrderedDictionary: $($Context.Message)" -InformationAction Continue
        }

        function Use-TestWithOrderedDictionary {
            [CmdletBinding()]
            param (
                [Parameter(Mandatory = $true)]
                [string]
                $Message
            )

            Write-Information -MessageData "INFO -- Use-TestWithOrderedDictionary: $Message" -InformationAction Continue

            $testContext = [ordered]@{
                Message = $Message
            }

            Test-WithOrderedDictionary -Context $testContext
        }

        function Test-WithHashTable {
            [CmdletBinding()]
            param (
                [Parameter(Mandatory = $true)]
                [hashtable]
                $Context
            )

            Write-Information -MessageData "INFO -- Test-WithHashTable: $($Context.Message)" -InformationAction Continue
        }

        function Use-TestWithHashTable {
            [CmdletBinding()]
            param (
                [Parameter(Mandatory = $true)]
                [string]
                $Message
            )

            Write-Information -MessageData "INFO -- Use-TestWithHashTable: $Message" -InformationAction Continue

            $testContext = @{
                Message = $Message
            }

            Test-WithHashTable -Context $testContext
        }
    }

    Context 'Test-WithOrderedDictionary' {
        It 'With mock throws error with PowerShell 7, but works with PowerShell 5' {

            Mock -CommandName 'Test-WithOrderedDictionary'

            Use-TestWithOrderedDictionary -Message 'With mock throws error with PowerShell 7, but works with PowerShell 5'
        }

        It 'Without mock runs fine with PowerShell 7 and PowerShell 5' {

            Use-TestWithOrderedDictionary -Message 'Without mock runs fine with PowerShell 7 and PowerShell 5'
        }
    }

    Context 'Test-WithHashTable' {
        It 'With mock runs fine with PowerShell 7 and PowerShell 5' {

            Mock -CommandName 'Test-WithHashTable'

            Use-TestWithHashTable -Message 'With mock runs fine with PowerShell 7 and PowerShell 5'
        }

        It 'Without mock runs fine with PowerShell 7 and PowerShell 5' {

            Use-TestWithHashTable -Message 'Without mock runs fine with PowerShell 7 and PowerShell 5'
        }
    }
}

Describe your environment

Pester version : 5.4.1 C:\Program Files\PowerShell\Modules\Pester\5.4.1\Pester.psm1
PowerShell version : 7.3.4
OS version : Microsoft Windows NT 10.0.19044.0

Possible Solution?

It's not a solution but as a workaround one can use a hashtable instead of an ordered dictionary.

[fflaten]

Hi. Thanks for the report. This is caused by a bug in PowerShell itself.

# Define the function
function Test-WithOrderedDictionary {
    [CmdletBinding()]
    param (
        [Parameter(Mandatory = $true)]
        [System.Collections.Specialized.OrderedDictionary]
        $Context
    )

    Write-Information -MessageData "INFO -- Test-WithOrderedDictionary: $($Context.Message)" -InformationAction Continue
}

# Generate proxycommand paramblock in Windows PowerShell 5.1
> [System.Management.Automation.ProxyCommand]::GetParamBlock((Get-Command Test-WithOrderedDictionary))

    [Parameter(Mandatory=$true, Position=0)]
    [System.Collections.Specialized.OrderedDictionary]
    ${Context}

# Generate proxycommand paramblock in PowerShell 7.3
> [System.Management.Automation.ProxyCommand]::GetParamBlock((Get-Command Test-WithOrderedDictionary))

    [Parameter(Mandatory=$true, Position=0)]
    [ordered]
    ${Context}

Unfortunately I'm actually the one who introduced this bug in PS 7.3 by making [ordered] a proper type accelerator in PowerShell/PowerShell#17804. It seems the proxy command generator prefers the accelerator now, but that will fail as [ordered] has a special guard to block it from being used like this. That's something the working group decided to keep as-is, though not with this scenario in mind, see PowerShell/PowerShell#10513 (comment).

I'll submit an issue in the PowerShell-repo so we hopefully can fix this in a future PowerShell-release.