ValidateSet with class does not work

Prerequisites

• Write a descriptive title.
• Make sure you are able to repro it on the latest released version
• Search the existing issues.
• Refer to the FAQ.
• Refer to Differences between Windows PowerShell 5.1 and PowerShell.

Steps to reproduce

Create two files in a directory.

test.ps1

using module './testvalidate.psm1'

param
(
    [Parameter(Mandatory)]
    [ValidateSet([TestValidate])]
    [string]$foo
)

testvalidate.psm1

class TestValidate : System.Management.Automation.IValidateSetValuesGenerator
{
    [String[]] GetValidValues()
    {
        $values = @()
        $values += 'bar'
        $values += 'baz'
        return $values
    }
}

Expected behavior

cmdlet test.ps1 at command pipeline position 1
Supply values for the following parameters:
foo:

Actual behavior

InvalidOperation: E:\Software development\Royalty Calculator\trunk.powershell\test.ps1:6
Line |
   6 |      [ValidateSet([TestValidate])]
     |      ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
     | Unable to find type [TestValidate].

Error details

Exception             :
    Type        : System.Management.Automation.RuntimeException
    ErrorRecord :
        Exception             :
            Type    : System.Management.Automation.ParentContainsErrorRecordException
            Message : Unable to find type [TestValidate].
            HResult : -2146233087
        TargetObject          : [ValidateSet([TestValidate])]
        CategoryInfo          : InvalidOperation: ([ValidateSet([TestValidate])]:AttributeAst) [], ParentContainsErrorRecordException
        FullyQualifiedErrorId : TypeNotFound
        InvocationInfo        :
            ScriptLineNumber : 6
            OffsetInLine     : 5
            HistoryId        : -1
            ScriptName       : E:\Software development\Royalty Calculator\trunk.powershell\test.ps1
            Line             : [ValidateSet([TestValidate])]

            PositionMessage  : At E:\Software development\Royalty Calculator\trunk.powershell\test.ps1:6 char:5
                               +     [ValidateSet([TestValidate])]
                               +     ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
            PSScriptRoot     : E:\Software development\Royalty Calculator\trunk.powershell
            PSCommandPath    : E:\Software development\Royalty Calculator\trunk.powershell\test.ps1
            CommandOrigin    : Internal
        ScriptStackTrace      : at <ScriptBlock>, <No file>: line 1
    TargetSite  :
        Name          : NewValidateSetAttribute
        DeclaringType : System.Management.Automation.Language.Compiler, System.Management.Automation, Version=7.3.4.500, Culture=neutral, PublicKeyToken=31bf3856ad364e35
        MemberType    : Method
        Module        : System.Management.Automation.dll
    Message     : Unable to find type [TestValidate].
    Data        : System.Collections.ListDictionaryInternal
    Source      : System.Management.Automation
    HResult     : -2146233087
    StackTrace  :
   at System.Management.Automation.Language.Compiler.NewValidateSetAttribute(AttributeAst ast)
   at System.Management.Automation.Language.Compiler.GetAttribute(AttributeAst attributeAst)
   at System.Management.Automation.Language.Compiler.GetRuntimeDefinedParameter(ParameterAst parameterAst, Boolean& customParameterSet, Boolean& usesCmdletBinding)
   at System.Management.Automation.Language.Compiler.GetParameterMetaData(ReadOnlyCollection`1 parameters, Boolean automaticPositions, Boolean& usesCmdletBinding)
   at System.Management.Automation.CompiledScriptBlockData.InitializeMetadata()
   at System.Management.Automation.CompiledScriptBlockData.Compile(Boolean optimized)
   at System.Management.Automation.PSScriptCmdlet..ctor(ScriptBlock scriptBlock, Boolean useNewScope, Boolean fromScriptFile, ExecutionContext context)
   at System.Management.Automation.CommandProcessor.Init(IScriptCommandInfo scriptCommandInfo)
   at System.Management.Automation.CommandDiscovery.GetScriptAsCmdletProcessor(IScriptCommandInfo scriptCommandInfo, ExecutionContext context, Boolean useNewScope, Boolean fromScriptFile, SessionStateInternal sessionState)
   at System.Management.Automation.CommandDiscovery.CreateCommandProcessorForScript(ExternalScriptInfo scriptInfo, ExecutionContext context, Boolean useNewScope, SessionStateInternal sessionState)
   at System.Management.Automation.CommandDiscovery.CreateScriptProcessorForSingleShell(ExternalScriptInfo scriptInfo, ExecutionContext context, Boolean useLocalScope, SessionStateInternal sessionState)
   at System.Management.Automation.CommandDiscovery.LookupCommandProcessor(CommandInfo commandInfo, CommandOrigin commandOrigin, Nullable`1 useLocalScope, SessionStateInternal sessionState)
   at System.Management.Automation.CommandDiscovery.LookupCommandProcessor(String commandName, CommandOrigin commandOrigin, Nullable`1 useLocalScope)
   at System.Management.Automation.ExecutionContext.CreateCommand(String command, Boolean dotSource)
   at System.Management.Automation.PipelineOps.AddCommand(PipelineProcessor pipe, CommandParameterInternal[] commandElements, CommandBaseAst commandBaseAst, CommandRedirection[] redirections, ExecutionContext context)
   at System.Management.Automation.PipelineOps.InvokePipeline(Object input, Boolean ignoreInput, CommandParameterInternal[][] pipeElements, CommandBaseAst[] pipeElementAsts, CommandRedirection[][] commandRedirections, FunctionContext funcContext)
   at System.Management.Automation.Interpreter.ActionCallInstruction`6.Run(InterpretedFrame frame)
   at System.Management.Automation.Interpreter.EnterTryCatchFinallyInstruction.Run(InterpretedFrame frame)
TargetObject          : [ValidateSet([TestValidate])]
CategoryInfo          : InvalidOperation: ([ValidateSet([TestValidate])]:AttributeAst) [], RuntimeException
FullyQualifiedErrorId : TypeNotFound
InvocationInfo        :
    ScriptLineNumber : 6
    OffsetInLine     : 5
    HistoryId        : -1
    ScriptName       : E:\Software development\Royalty Calculator\trunk.powershell\test.ps1
    Line             : [ValidateSet([TestValidate])]

    PositionMessage  : At E:\Software development\Royalty Calculator\trunk.powershell\test.ps1:6 char:5
                       +     [ValidateSet([TestValidate])]
                       +     ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
    PSScriptRoot     : E:\Software development\Royalty Calculator\trunk.powershell
    PSCommandPath    : E:\Software development\Royalty Calculator\trunk.powershell\test.ps1
    CommandOrigin    : Internal
ScriptStackTrace      : at <ScriptBlock>, <No file>: line 1

Environment data

Name                           Value
----                           -----
PSVersion                      7.3.4
PSEdition                      Core
GitCommitId                    7.3.4
OS                             Microsoft Windows 10.0.19045
Platform                       Win32NT
PSCompatibleVersions           {1.0, 2.0, 3.0, 4.0…}
PSRemotingProtocolVersion      2.3
SerializationVersion           1.1.0.1
WSManStackVersion              3.0

Visuals

No response

[mklement0]

There is a workaround, but it is somewhat cumbersome: It relies on the fact that referencing types in script blocks used in parameter attributes happens at runtime, so the imported type is then already available:

using module ./testvalidate.psm1

param(
    [Parameter(Mandatory)]
    [ValidateScript({ 
      if ($_ -notin [TestValidate]::new().GetValidValues()) { throw "Not a valid value: $_" }
      $true
    })]
    [ArgumentCompleter({ 
      param($command, $param, $wordToComplete)
      [TestValidate]::new().GetValidValues() -like "$wordToComplete*"
    })]
    [string]$foo
)

The unfortunate side effect of using ArgumentCompleter with a script block (rather than with an IArgumentCompleter-implementing class) is that if what the user typed doesn’t match any of the valid values, the default file-name completion behavior kicks in; see:

• #19628

[rhubarb-geek-nz]

I would expect so. For tab completion to work I expect it needs to have access to all the classes to do the value matching. If all the command line interpreter does is read the param stanza then it won’t have enough information. I don’t expect that tab-completion is done by actually running the script.

about_Functions_Argument_Completion

Can you not do something like their example?

Param(
    [ValidateSet('hello', 'world')]
    [string]$Message
)

$Message = 'bye'

The auto-completion offered both ‘hello’ and ‘world’ as options

This also errors when you try and assign ‘bye’ to $Message