Adding ValidatePlatform Transpiler (#58)

Author: James Brundage

Transpilers/Parameters/ValidatePlatform.psx.ps1

@@ -0,0 +1,69 @@
+<#
+.SYNOPSIS
+    Validates the Platform    
+.DESCRIPTION
+    Validates the Platform.
+    
+    When used within Parameters, this adds a ```[ValidateScript({})]``` to ensure that the platform is correct.
+
+    When used on a ```[Management.Automation.Language.VariableExpressionAst]``` will apply a 
+    ```[ValidateScript({})]``` to that variable, which will prevent assignemnt to the variable if not on the platform.
+.EXAMPLE
+    {
+        param(
+        [ValidatePlatform("Windows")]
+        [switch]
+        $UseWMI
+        )
+    } | .>PipeScript
+#>
+[CmdletBinding(DefaultParameterSetName='Parameter')]
+param(
+# The name of one or more platforms.  These will be interpreted as wildcards.
+[Parameter(Mandatory,Position=0)]
+[string[]]
+$Platform,
+
+[Parameter(ValueFromPipeline,ParameterSetName='VariableExpressionAST')]
+[Management.Automation.Language.VariableExpressionAST]
+$VariableAST
+)
+
+$Platform = @($Platform -replace 'Windows', 'Win*')
+
+$checkPlatform = @"
+`$platformList = '$($Platform -join "','")'
+"@ + {
+$platformOK = ($platFormList -like 'Win*' -and $(
+    $winPlat = @($platFormList -like 'Win*')[0]
+    (-not $psVersionTable.Platform) -or $psVersionTable.Platform -like $winPlat
+)) -or $(
+    foreach ($platform in $platformList) {
+        if ($psVersionTable.Platform -like $platform) {
+            $true;break
+        }
+    }
+)
+}
+
+if ($PSCmdlet.ParameterSetName -eq 'Parameter') {
+
+    [ScriptBlock]::Create(@"
+[ValidateScript({
+`$ok = `$false
+$checkPlatform
+`$ok = `$platformOK
+if (-not `$ok) {
+    throw "Incorrect Platform: '`$(`$psVersionTable.Platform)'.  Must be like '$($Platform -join "','")'."
+}
+})]
+$(
+    if ($psCmdlet.ParameterSetName -eq 'Parameter') {
+        'param()'
+    } else {
+        '$' + $VariableAST.variablePath.ToString()
+    }
+)
+"@)
+
+}