Merge pull request #12578 from trondhindenes/powershell_getattr_improvements2

Windows: Added parameter validation to the get-attr function / Get-AnsibleParam 

lib/ansible/module_utils/powershell.ps1

@@ -101,9 +101,11 @@ Function Fail-Json($obj, $message = $null)
 # Helper function to get an "attribute" from a psobject instance in powershell.
 # This is a convenience to make getting Members from an object easier and
 # slightly more pythonic
-# Example: $attr = Get-Attr $response "code" -default "1"
+# Example: $attr = Get-AnsibleParam $response "code" -default "1"
+#Get-AnsibleParam also supports Parameter validation to save you from coding that manually:
+#Example: Get-AnsibleParam -obj $params -name "State" -default "Present" -ValidateSet "Present","Absent" -resultobj $resultobj -failifempty $true
 #Note that if you use the failifempty option, you do need to specify resultobject as well.
-Function Get-Attr($obj, $name, $default = $null, $resultobj, $failifempty=$false, $emptyattributefailmessage)
+Function Get-AnsibleParam($obj, $name, $default = $null, $resultobj, $failifempty=$false, $emptyattributefailmessage, $ValidateSet, $ValidateSetErrorMessage)
 {
     # Check if the provided Member $name exists in $obj and return it or the default. 
     Try
@@ -112,7 +114,28 @@ Function Get-Attr($obj, $name, $default = $null, $resultobj, $failifempty=$false
         {
             throw
         }
-        $obj.$name
+
+        if ($ValidateSet)
+        {
+            if ($ValidateSet -contains ($obj.$name))
+            {
+                $obj.$name    
+            }
+            Else
+            {
+                if ($ValidateSetErrorMessage -eq $null)
+                {
+                    #Auto-generated error should be sufficient in most use cases
+                    $ValidateSetErrorMessage = "Argument $name needs to be one of $($ValidateSet -join ",") but was $($obj.$name)."
+                }
+                Fail-Json -obj $resultobj -message $ValidateSetErrorMessage
+            }
+        }
+        Else
+        {
+            $obj.$name
+        }
+        
     }
     Catch
     {
@@ -131,6 +154,9 @@ Function Get-Attr($obj, $name, $default = $null, $resultobj, $failifempty=$false
     }
 }
 
+#Alias Get-attr-->Get-AnsibleParam for backwards compat.
+New-Alias -Name Get-attr -Value Get-AnsibleParam
+
 # Helper filter/pipeline function to convert a value to boolean following current
 # Ansible practices
 # Example: $is_true = "true" | ConvertTo-Bool