Adding ProxyCommand (#51)

Author: James Brundage

Transpilers/ProxyCommand.psx.ps1

@@ -0,0 +1,105 @@
+<#
+.SYNOPSIS
+    Creates Proxy Commands
+.DESCRIPTION
+    Generates a Proxy Command for an underlying PowerShell or PipeScript command.
+.EXAMPLE
+    .\ProxyCommand.psx.ps1 -CommandName Get-Process
+.EXAMPLE
+    {
+        function [ProxyCommand<'Get-Process'>]GetProcessProxy {}
+    } | .>PipeScript
+.EXAMPLE
+    .>ProxyCommand -CommandName Get-Process -RemoveParameter *
+.EXAMPLE
+    Invoke-PipeScript -ScriptBlock {[ProxyCommand('Get-Process')]param()}
+.EXAMPLE
+    Invoke-PipeScript -ScriptBlock {
+        [ProxyCommand('Get-Process', 
+            RemoveParameter='*',
+            DefaultParameter={
+                @{id='$pid'}
+            })]
+            param()
+    }
+.EXAMPLE
+    { 
+        function Get-MyProcess {
+            [ProxyCommand('Get-Process', 
+                RemoveParameter='*',
+                DefaultParameter={
+                    @{id='$pid'}
+                })]
+                param()
+        } 
+    } | .>PipeScript
+#>
+param(
+# The ScriptBlock that will become a proxy command.  This should be empty, since it is ignored.
+[Parameter(ValueFromPipeline)]
+[scriptblock]
+$ScriptBlock,
+
+# The name of the command being proxied.
+[Parameter(Mandatory,Position=0)]
+[string]
+$CommandName,
+
+# If provided, will remove any number of parameters from the proxy command.
+[string[]]
+$RemoveParameter,
+
+# Any default parameters for the ProxyCommand.
+[Collections.IDictionary]
+$DefaultParameter
+)
+
+$resolvedCommand = $ExecutionContext.SessionState.InvokeCommand.GetCommand($CommandName, 'Alias,Function,Cmdlet')
+if (-not $resolvedCommand) {
+    Write-Error "Could not resolve -CommandName '$CommandName'"
+    return
+}
+
+$commandMetadata = [Management.Automation.CommandMetadata]$resolvedCommand
+
+if ($RemoveParameter) {    
+    $toRemove = @(
+        foreach ($paramName in $commandMetadata.Parameters.Keys) {
+            if ($RemoveParameter -contains $paramName) {
+                $paramName
+            } else {
+                foreach ($rp in $RemoveParameter) {
+                    if ($paramName -like $rp) {
+                        $paramName
+                        break
+                    }
+                }
+            }
+        }
+    )
+
+    $null = foreach ($tr in $toRemove) {
+        $commandMetadata.Parameters.Remove($tr)
+    }
+}
+
+$proxyCommandText = [Management.Automation.ProxyCommand]::Create($commandMetadata)
+
+if ($DefaultParameter) {
+    $toSplat = "@'
+$(ConvertTo-Json $DefaultParameter -Depth 100)
+'@"
+$insertPoint = $proxyCommandText.IndexOf('$scriptCmd = {& $wrappedCmd @PSBoundParameters }')
+$proxyCommandText = $proxyCommandText.Insert($insertPoint,@"
+        `$_DefaultParameters = ConvertFrom-Json $toSplat                
+        foreach (`$property in `$_DefaultParameters.psobject.properties) {
+            `$psBoundParameters[`$property.Name] = `$property.Value
+            if (`$property.Value -is [string] -and `$property.Value.StartsWith('`$')) {
+                `$psBoundParameters[`$property.Name] = `$executionContext.SessionState.PSVariable.Get(`$property.Value.Substring(1)).Value
+            }
+        }
+"@)
+
+}
+
+[ScriptBlock]::Create($proxyCommandText)