Reject parameters not in Param() statement-CodePudding

I have a powershell script that starts with

Param([switch]$NoDownload, [switch]$NoUnpack, [switch]$NoExtract, [switch]$NoImport, [switch]$NoBackup)

and I was very happy because I thought that it would provide automatic parameter validation. Until one day I made a mistake and wrote:

powershell -f myscript.ps1 -NoDowload

(notice the lack of n), and it happily downloaded something I didn't want it to.

How do I tell the powershell parameter handling machinery that the only valid parameters are the ones I explicitly state in the Param statement?

CodePudding user response：

Add a CmdletBinding attribute to the param() block - this makes PowerShell treat your script/function like a cmdlet - rather than a "simple" function - and it will apply much more rigorous parameter binding validation, including throwing errors when you attempt to bind a non-existing parameter name:

[CmdletBinding()]
param(
  [switch]$NoDownload,
  [switch]$NoUnpack,
  [switch]$NoExtract,
  [switch]$NoImport,
  [switch]$NoBackup
)

PS ~> .\myScript.ps1 -NoDowload
myScript.ps1 : A parameter cannot be found that matches parameter name 'NoDowload'.
At line:1 char:16
  .\myScript.ps1 -NoDowload
                 ~~~~~~~~~~
      CategoryInfo          : InvalidArgument: (:) [myScript.ps1], ParentContainsErrorRecordException
      FullyQualifiedErrorId : NamedParameterNotFound,myScript.ps1

Adding an explicit [Parameter()] attribute to any defined parameter will also implicitly make PowerShell treat your script/function as "advanced", even in the absence of a [CmdletBinding()] attribute:

param(
  [switch]$NoDownload,
  [switch]$NoUnpack,
  [switch]$NoExtract,
  [switch]$NoImport,
  [switch]$NoBackup,
  [Parameter(Mandatory = $false, DontShow = $true)]
  $DummyParameterThatTriggersCmdletBinding
)