Is there a way to access the unenumerated argument in [ValidateScript()]?

[alx9r]

It appears that [ValidateScript()] performs conditional enumeration on the argument before invoking the validation script. Is there a way to access the unenumerated argument from the validation script?

Steps to reproduce

function f {
    param
    (
        [ValidateScript({($_[0] -eq 1) -and ($_[1] -eq 2)})]$x
    )
    'success'
}

f -x 1,2

Expected behavior

success

Actual behavior

f : Cannot validate argument on parameter 'x'. The "($_[0] -eq 1) -and ($_[1] -e
q 2)" validation script for the argument with value "1" did not return a result
of True. Determine why the validation script failed, and then try the command ag
ain.
At C:\test.ps1:9 char:6
+ f -x 1,2
+      ~~~
+ CategoryInfo          : InvalidData: (:) [f], ParameterBindingValidationExcept
ion
+ FullyQualifiedErrorId : ParameterArgumentValidationError,f

Environment data

> $PSVersionTable

Name                           Value                                            
----                           -----                                            
PSVersion                      6.0.0                                            
PSEdition                      Core                                             
GitCommitId                    v6.0.0                                           
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]

Interesting find.

I'd say that the right behavior is to pass the bound parameter value as-is, whether it happens to be a scalar or an array; no enumeration should be applied, so the current behavior is definitely unexpected.

Just to state it explicitly: In your example, the validation script block is unexpectedly called once for each array element, with $_ bound to that element, even though you're passing the array as a single value.

[rmbolger]

The mind boggling thing is that it happens even when the parameter is explicitly typed as an array. It has been this way since at least PowerShell 3. I haven't personally tested any further back. It makes validating an array as a whole basically impossible with ValidateScript which is annoying for things like byte arrays that are used a ton in crypto stuff.

Here's a more visual example.

function Test-ByteArray {
    [CmdletBinding()]
    param(
        [Parameter(Mandatory,Position=0)]
        [ValidateScript({
            Write-Verbose "(Validate)     Type: $($_.GetType())"
            Write-Verbose "(Validate)   Length: $($_.Length)"
            Write-Verbose "(Validate) Contents: $($_ -join ',')"
            return $true

        })]
        [byte[]]$InputObject
    )

    Write-Verbose "(Function)     Type: $($InputObject.GetType())"
    Write-Verbose "(Function)   Length: $($InputObject.Length)"
    Write-Verbose "(Function) Contents: $($InputObject -join ',')"

}

$VerbosePreference = 'Continue'
$bytes = [byte[]]@(27,42,35)
Test-ByteArray $bytes

Output:

VERBOSE: (Validate)     Type: byte
VERBOSE: (Validate)   Length: 1
VERBOSE: (Validate) Contents: 27
VERBOSE: (Validate)     Type: byte
VERBOSE: (Validate)   Length: 1
VERBOSE: (Validate) Contents: 42
VERBOSE: (Validate)     Type: byte
VERBOSE: (Validate)   Length: 1
VERBOSE: (Validate) Contents: 35
VERBOSE: (Function)     Type: byte[]
VERBOSE: (Function)   Length: 3
VERBOSE: (Function) Contents: 27,42,35

[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.