Enable `export` for class-based resources

[SteveL-MSFT]

Summary of the new feature / enhancement

Enable class-based resources to participate in DSCv3 export capability

Proposed technical implementation details (optional)

No response

[michaeltlombardi]

The PowerShell adapter for DSCv3 is implemented to support export for PSDSC Resources when the resource has a static Export method that takes no parameters and returns an array of the PSDSC Resource class.

https://github.com/PowerShell/DSC/blob/0157276b2ada32da5859ce930f4cae2e592f586c/powershell-adapter/psDscAdapter/psDscAdapter.psm1#L296-L301

Following is an example signature for the Export method, using MyDscResource as the class name:

static [MyDscResource[]] Export() {
    # Code to return the array of all instances for the resource
}

However, the PSDesiredStateConfiguration module doesn't know about or handle the Export method at all.

[Gijsreyn]

Mikey Lombardi (He/Him) (@michaeltlombardi) Will the DSCv3 implementation support parameters in the future? I guess the PR on VSCodeExtension in the winget-dsc repository broke the participation now.

[michaeltlombardi]

Mikey Lombardi (He/Him) (@michaeltlombardi) Will the DSCv3 implementation support parameters in the future?

It's possible - I don't think parameterized export is fully settled yet in general, but in that case I would expect the class-based resource to define the following static methods to fully implement the export capability:

[DscResourceClassName[]] Export() {
  return [DscResourceClassName]::Export($null)
}

[DscResourceClassName[]] Export([DscResourceClassName]$filterProperties) {
  # logic to get all instances and save in $instances
  if ($null -eq $filterProperties) {
    return $instances
  }
  # logic to filter instances
  return $instances
}