Add an option for PowerShell modules to indicate support for check mode, skip…

Add an option for PowerShell modules to indicate support for check mode, skip running module if check mode is not supported.

lib/ansible/module_utils/powershell.ps1

@@ -35,19 +35,6 @@ $complex_args = @'
 Set-Content env:MODULE_COMPLEX_ARGS -Value $complex_args
 $args = @('env:MODULE_COMPLEX_ARGS')
 
-# Helper function to parse Ansible JSON arguments from a "file" passed as
-# the single argument to the module.
-# Example: $params = Parse-Args $args
-Function Parse-Args($arguments)
-{
-    $parameters = New-Object psobject;
-    If ($arguments.Length -gt 0)
-    {
-        $parameters = Get-Content $arguments[0] | ConvertFrom-Json;
-    }
-    $parameters;
-}
-
 # Helper function to set an "attribute" on a psobject instance in powershell.
 # This is a convenience to make adding Members to the object easier and
 # slightly more pythonic
@@ -151,6 +138,28 @@ Function ConvertTo-Bool
     return
 }
 
+# Helper function to parse Ansible JSON arguments from a "file" passed as
+# the single argument to the module.
+# Example: $params = Parse-Args $args
+Function Parse-Args($arguments, $supports_check_mode = $false)
+{
+    $parameters = New-Object psobject
+    If ($arguments.Length -gt 0)
+    {
+        $parameters = Get-Content $arguments[0] | ConvertFrom-Json
+    }
+    $check_mode = Get-Attr $parameters "_ansible_check_mode" $false | ConvertTo-Bool
+    If ($check_mode -and -not $supports_check_mode)
+    {
+        $obj = New-Object psobject
+        Set-Attr $obj "skipped" $true
+        Set-Attr $obj "changed" $false
+        Set-Attr $obj "msg" "remote module does not support check mode"
+        Exit-Json $obj
+    }
+    $parameters
+}
+
 # Helper function to calculate a hash of a file in a way which powershell 3 
 # and above can handle:
 Function Get-FileChecksum($path)