PSDSC Resource data in `Set` and `Test` break naive expectations

[michaeltlombardi]

Prerequisites

• [X] Write a descriptive title.
• [X] Make sure you are able to repro it on the latest version
• [X] Search the existing issues.

Steps to reproduce

1. Create the files for a new PowerShell module

   mkdir ./dsc-repro/psdsc.repro
   touch ./dsc-repro/psdsc.repro/psdsc.repro.psd1
   touch ./dsc-repro/psdsc.repro/psdsc.repro.psm1
   

2. Define the module manifest:

   @{
       RootModule           = 'psdsc.repro.psm1'
       ModuleVersion        = '0.0.1'
       GUID                 = '361fff1b-423a-423f-9e05-39f5ab94a437'
       Author               = 'Bug Reproducer'
       CompanyName          = 'Unknown'
       Copyright            = '(c) Bug Reproducer. All rights reserved.'
       FunctionsToExport    = '*'
       CmdletsToExport      = '*'
       VariablesToExport    = '*'
       AliasesToExport      = '*'
       DscResourcesToExport = @(
           'ReproResultData'
       )
       PrivateData          = @{ PSData = @{} }
   }
   

3. Define the root module script:

   
   [DscResource()] class ReproResultData {
       [DscProperty(Key)] [string] $KeyProperty
       [DscProperty()]    [string] $ValueProperty
   
       [ReproResultData] Get() {
           $Current               = [ReproResultData]::new()
           $Current.KeyProperty   = $this.KeyProperty
           $Current.ValueProperty = "Default"
   
           return $Current
       }
   
       [bool] Test() { return $true }
       [void] Set()  { }
   }
   

4. Add the folder containing the repro module to the PSModulePath:

   $env:PSModulePath += [System.IO.Path]::PathSeparator + "$PWD/dsc-repro"
   

5. Confirm you can get the ReproResultData dsc resource and see its properties:

   $Resource = Get-DscResource -Module psdsc.repro
   

   ImplementationDetail : ClassBased
   ResourceType         : ReproResultData
   Name                 : ReproResultData
   FriendlyName         :
   Module               : psdsc.repro
   ModuleName           : psdsc.repro
   Version              : 0.0.1
   Path                 : C:\code\dsc-repro\psdsc.repro\psdsc.repro.psd1
   ParentPath           : C:\code\dsc-repro\psdsc.repro
   ImplementedAs        : PowerShell
   CompanyName          : Unknown
   Properties           : {KeyProperty, DependsOn, EnumProperty, PsDscRunAsCredential}
   

   $Resource | Select-Object -ExpandProperty Properties | Format-Table
   

   Name                 PropertyType   IsMandatory Values
   ----                 ------------   ----------- ------
   KeyProperty          [string]              True {}
   DependsOn            [string[]]           False {}
   PsDscRunAsCredential [PSCredential]       False {}
   ValueProperty        [string]             False {}
   

   dsc --format yaml resource list psdsc.repro/ReproResultData
   

   # Formatted for easier reading
   type          : psdsc.repro/ReproResultData
   version       : 0.0.1
   path          : C:\code\dsc-repro\psdsc.repro\psdsc.repro.psd1
   description   : null
   directory     : C:\code\dsc-repro\psdsc.repro
   implementedAs : ClassBased
   author        : ''
   properties    : [
                       KeyProperty,
                       DependsOn,
                       PsDscRunAsCredential,
                       ValueProperty
                   ]
   requires      : DSC/PowerShellGroup
   manifest      : null
   

6. Invoke the resource with Invoke-DscResource

   $PSInvokeParams = @{
       Module   = 'psdsc.repro'
       Name     = 'ReproResultData'
       Property = @{
           KeyProperty   = 'Repro Example (PSDSC)'
           ValueProperty = 'Desired'
       }
   }
   'Get', 'Test', 'Set' | ForEach-Object {
       Invoke-DscResource -Method $_  @PSInvokeParams | Format-List
   }
   

   KeyProperty   : Repro Example (PSDSC)
   ValueProperty : Default
   ---
   InDesiredState : False
   ---
   RebootRequired : False
   

7. Invoke the resource with dsc resource:

   foreach ($Method in @('get', 'test', 'set')) {
        $InputJson = @{
            KeyProperty   = 'Repro Example (DSCv3)'
            ValueProperty = 'Desired'
        } | ConvertTo-Json
        $Arguments = @(
            $Method
            '-r', 'psdsc.repro/ReproResultData'
            '-i', $InputJson
        )
        dsc resource @Arguments
   }
   

   actualState:
     KeyProperty: Repro Example (DSCv3)
     ValueProperty: Default
   ---
   desiredState:
     KeyProperty: Repro Example (DSCv3)
     ValueProperty: Desired
     type: psdsc.repro/ReproResultData
   actualState:
     InDesiredState: false
   inDesiredState: false
   differingProperties:
   - KeyProperty
   - ValueProperty
   - type
   ---
   beforeState:
     KeyProperty: Repro Example (DSCv3)
     ValueProperty: Default
   afterState:
     RebootRequired: false
   changedProperties:
   - RebootRequired
   

Expected behavior

$PSInvokeParams = @{
    Module   = 'psdsc.repro'
    Name     = 'ReproResultData'
    Property = @{
        KeyProperty   = 'Repro Example (PSDSC)'
        ValueProperty = 'Desired'
    }
}
'Get', 'Test', 'Set' | ForEach-Object {
    Invoke-DscResource -Method $_  @PSInvokeParams | Format-List
}

KeyProperty   : Repro Example (PSDSC)
ValueProperty : Default
---
InDesiredState : False
---
RebootRequired : False

foreach ($Method in @('get', 'test', 'set')) {
    $InputJson = @{
        KeyProperty   = 'Repro Example (DSCv3)'
        ValueProperty = 'Desired'
    } | ConvertTo-Json
    $Arguments = @(
        $Method
        '-r', 'psdsc.repro/ReproResultData'
        '-i', $InputJson
    )
    dsc resource @Arguments
}

actualState:
  KeyProperty:   Repro Example (PSDSC)
  ValueProperty: Default
---
desiredState:
  KeyProperty:   Repro Example (PSDSC)
  ValueProperty: Desired
actualState:
  KeyProperty:    Repro Example (PSDSC)
  ValueProperty:  Default
  InDesiredState: false # should be ignored in property comparison
inDesiredState: false
differingProperties:
- ValueProperty
---
beforeState:
  KeyProperty:   Repro Example (PSDSC)
  ValueProperty: Default
afterState:
  KeyProperty:    Repro Example (PSDSC)
  ValueProperty:  Default
  RebootRequired: false # should be ignored in property comparison
changedProperties: []   # empty because set isn't implemented

Actual behavior

$PSInvokeParams = @{
    Module   = 'psdsc.repro'
    Name     = 'ReproResultData'
    Property = @{
        KeyProperty   = 'Repro Example (PSDSC)'
        ValueProperty = 'Desired'
    }
}
'Get', 'Test', 'Set' | ForEach-Object {
    Invoke-DscResource -Method $_  @PSInvokeParams | Format-List
}

KeyProperty   : Repro Example (PSDSC)
ValueProperty : Default
---
InDesiredState : False
---
RebootRequired : False

foreach ($Method in @('get', 'test', 'set')) {
    $InputJson = @{
        KeyProperty   = 'Repro Example (DSCv3)'
        ValueProperty = 'Desired'
    } | ConvertTo-Json
    $Arguments = @(
        $Method
        '-r', 'psdsc.repro/ReproResultData'
        '-i', $InputJson
    )
    dsc resource @Arguments
}

actualState:
  KeyProperty:   Repro Example (PSDSC)
  ValueProperty: Default
---
desiredState:
  KeyProperty:   Repro Example (PSDSC)
  ValueProperty: Desired
  type:          psdsc.repro/ReproResultData
actualState:
  InDesiredState: false
inDesiredState: false
differingProperties:
- KeyProperty
- ValueProperty
- type
---
beforeState:
  KeyProperty:   Repro Example (PSDSC)
  ValueProperty: Default
afterState:
  RebootRequired: false
changedProperties:
- RebootRequired

Error details

No response

Environment data

Name                           Value
----                           -----
PSVersion                      7.3.6
PSEdition                      Core
GitCommitId                    7.3.6
OS                             Microsoft Windows 10.0.22621
Platform                       Win32NT
PSCompatibleVersions           {1.0, 2.0, 3.0, 4.0…}
PSRemotingProtocolVersion      2.3
SerializationVersion           1.1.0.1
WSManStackVersion              3.0

Version

DSC (build from main), PSDSC v2.0.7

Visuals

No response

Fix Proposal

The DSC/PowerShellGroup resource provider should handle munging the data before returning it to dsc - currently, it just passes through the JSONified output from Invoke-DscResource - this breaks the expectations for dsc resource test and dsc resource set, particularly for integrating tools and users unfamiliar with what's happening.

The resource provider could invoke the get method before test/set calls, caching the before state. For Set calls, it could call get again after the set operation.

We need further thought and discussion on how to handle the InDesiredState and RebootRequired values from PSDSC Resources.