Should -HaveParameter <parameter name> -HasArgumentCompleter does not cover all scenarios

[dtewinkel]

General summary of the issue

The assertion Should -HaveParameter <parameter name> -HasArgumentCompleter does not work for argument completers that are registered with Register-ArgumentCompleter.

Describe your environment

Pester version : 5.1.1 C:\Users\User\Documents\PowerShell\Modules\Pester\5.1.1\Pester.psm1
PowerShell version : 7.1.3
OS version : Microsoft Windows NT 10.0.19042.0

Steps to reproduce

Describe "Reproduce" {
	BeforeAll	{
		function Reproduce()
		{
			param(
				[Parameter()]
#				[ArgumentCompleter({param($Command, $Parameter, $WordToComplete, $CommandAst, $FakeBoundParams)})]
				[String] $Foo
			)
		}

		Register-ArgumentCompleter -CommandName Reproduce -ParameterName Foo -ScriptBlock {
			param($Command, $Parameter, $WordToComplete, $CommandAst, $FakeBoundParams)
		}

	}

	It "should pass" {
		Get-Command Reproduce | Should -HaveParameter Foo -HasArgumentCompleter
	}
}

Expected Behavior

The test should Pass. The Argument has an argument completer.

Current Behavior

The test fails with error:

[-] Reproduce.should pass 16ms (14ms|2ms)
 Expected command Reproduce to have a parameter Foo, has ArgumentCompletion, but has no ArgumentCompletion.
 at Get-Command Reproduce | Should -HaveParameter Foo -HasArgumentCompleter, Reproduce.Tests.ps1:19
 at <ScriptBlock>, Reproduce.Tests.ps1:19

Test will succeed with using the (commented out) ArgumentCompleter attribute.

[nohwnd]

@lipkau I think you were adding this? Any ideas?

[dtewinkel]

I guess this gist on github may help in solving this issue: Get-ArgumentCompleter.ps1.
It provides a way to find the registered argument completers.

[nohwnd]

@dtewinkel @indented-automation @lipkau Is anyone of you interested in making a PR for this? 🙂

[indented-automation]

I don't mind taking a look unless someone else gets there first :)

[dtewinkel]

Thank you @indented-automation. I am looking forward to the next release.

[nohwnd]

@dtewinkel there will be at least 2 pre releases till then. Please help us test it. I will try to make one this morning.

[dtewinkel]

@nohwnd, Sure, no problem. I'll try to have a look at it and test it in my project a.s.a.p.

[dtewinkel]

@nohwnd, @indented-automation, to me it is working as expected now :-). Both for succeeding the test if the argument completer is present and for failing the test if the argument completer is missing.