Add support for Enums as optional properties (#23)

Author: dan-hughes

CHANGELOG.md

@@ -5,8 +5,21 @@ and this project adheres to [Semantic Versioning](https://semver.org/spec/v2.0.0
 
 ## [Unreleased]
 
+### Added
+
+- `Resource.Base`
+  - Add optional feature flag to handle using Enums as optional properties.
+    This requires setting the starting value of the Enum to 1 so it is
+    initialized as 0. Fixes [Issue #22](https://github.com/dsccommunity/DscResource.Base/issues/22).
+
+    To use, set `$this.FeatureOptionalEnums = $true` in your class constructor.
+- `Clear-ZeroedEnumPropertyValue`
+  - Added private function to remove enums with a zero value from a hashtable.
+
 ### Changed
 
+- `ResourceBase`
+  - Add feature flag to allow use of enums on optional properties.
 - `RequiredModules`
   - Add PlatyPS
 - `Resolve-Dependency`

Resolve-Dependency.psd1

@@ -3,7 +3,7 @@
     AllowPrerelease                            = $false
     WithYAML                                   = $true # Will also bootstrap PowerShell-Yaml to read other config files
 
-    #UseModuleFast = $true
+    UseModuleFast                              = $true
     #ModuleFastVersion = '0.1.2'
     #ModuleFastBleedingEdge = $true
 

source/Classes/010.ResourceBase.ps1

@@ -19,6 +19,9 @@ class ResourceBase
     # Property for derived class to set properties that should not be enforced.
     hidden [System.String[]] $ExcludeDscProperties = @()
 
+    # Property for derived class to enable Enums to be used as optional properties. The usable Enum values should start at value 1.
+    hidden [System.Boolean] $FeatureOptionalEnums = $false
+
     # Default constructor
     ResourceBase()
     {
@@ -227,6 +230,11 @@ class ResourceBase
         # Get the desired state, all assigned properties that has an non-null value.
         $desiredState = $this | Get-DscProperty -Attribute @('Key', 'Mandatory', 'Optional') -HasValue
 
+        if ($this.FeatureOptionalEnums)
+        {
+            $desiredState = $desiredState | Clear-ZeroedEnumPropertyValue
+        }
+
         $CompareDscParameterState = @{
             CurrentValues     = $currentState
             DesiredValues     = $desiredState
@@ -250,6 +258,11 @@ class ResourceBase
         # Get the properties that has a non-null value and is not of type Read.
         $desiredState = $this | Get-DscProperty -Attribute @('Key', 'Mandatory', 'Optional') -HasValue
 
+        if ($this.FeatureOptionalEnums)
+        {
+            $desiredState = $desiredState | Clear-ZeroedEnumPropertyValue
+        }
+
         $this.AssertProperties($desiredState)
     }
 

source/Enum/1.Ensure.ps1

@@ -5,6 +5,6 @@
 
 enum Ensure
 {
-    Present
+    Present = 1
     Absent
 }

source/Private/Clear-ZeroedEnumPropertyValue.ps1

@@ -0,0 +1,47 @@
+<#
+    .SYNOPSIS
+        Removes any properties from a hashable which have values that are
+        type [System.Enum] and have an [System.Int32] value of 0.
+
+    .DESCRIPTION
+        Removes any properties from a hashable which have values that are
+        type [System.Enum] and have an [System.Int32] value of 0.
+
+    .PARAMETER InputObject
+        The hashtable to be checked.
+
+    .EXAMPLE
+        Clear-ZeroedEnumPropertyValue -InputObject $ht
+
+    .OUTPUTS
+        [System.Collections.Hashtable]
+#>
+
+function Clear-ZeroedEnumPropertyValue
+{
+    [CmdletBinding()]
+    [OutputType([System.Collections.Hashtable])]
+    param (
+        [Parameter(Mandatory = $true, ValueFromPipeline = $true)]
+        [System.Collections.Hashtable]
+        $InputObject
+    )
+
+    process
+    {
+        $result = @{}
+
+        foreach ($property in $InputObject.Keys)
+        {
+            $value = $InputObject.$property
+            if ($value.IsEnum -and [System.Int32]$value.value__ -eq 0)
+            {
+                continue
+            }
+
+            $result.$property = $value
+        }
+
+        return $result
+    }
+}

tests/Unit/Classes/Reason.Tests.ps1

@@ -10,7 +10,7 @@ BeforeDiscovery {
             if (-not (Get-Module -Name 'DscResource.Test' -ListAvailable))
             {
                 # Redirect all streams to $null, except the error stream (stream 2)
-                & "$PSScriptRoot/../../build.ps1" -Tasks 'noop' 2>&1 4>&1 5>&1 6>&1 > $null
+                & "$PSScriptRoot/../../../build.ps1" -Tasks 'noop' 3>&1 4>&1 5>&1 6>&1 > $null
             }
 
             # If the dependencies has not been resolved, this will throw an error.