PSUseProcessBlockForPipelineCommand does not recognize use of $input within an End block

Steps to reproduce

Invoke-ScriptAnalyzer -IncludeRule PSUseProcessBlockForPipelineCommand `
	-ScriptDefinition 'Param([Parameter(ValueFromPipeline=$true)][psobject] $Item); End {$input |ConvertTo-Json}'

Expected behavior

(no output)

Actual behavior

RuleName                            Severity     ScriptName Line  Message
--------                            --------     ---------- ----  -------
PSUseProcessBlockForPipelineCommand Warning                 1     Command accepts pipeline input but has not defined a
                                                                  process block.

Environment data

> $PSVersionTable

Name                           Value
----                           -----
PSVersion                      7.3.4
PSEdition                      Core
GitCommitId                    7.3.4
OS                             Microsoft Windows 10.0.22621
Platform                       Win32NT
PSCompatibleVersions           {1.0, 2.0, 3.0, 4.0…}
PSRemotingProtocolVersion      2.3
SerializationVersion           1.1.0.1
WSManStackVersion              3.0


> (Get-Module -ListAvailable PSScriptAnalyzer).Version | ForEach-Object { $_.ToString() }
1.21.0

[JamesWTruher]

@brianary using $input in the end is not something that we recommend and will likely lead to misunderstandings as the following example shows.

function f1 {
    param ([parameter(ValueFromPipeline=$true)]$a)
    BEGIN   { "input value: '$input' `tinput count: $($input.count) `tvalue of a: '$a'" }
    PROCESS { "input value: '$input' `tinput count: $($input.count) `tvalue of a: '$a'" }
    END     { "input value: '$input' `tinput count: $($input.count) `tvalue of a: '$a'" }
}

when run, the output is as follows:

PS> 1..3 | f1
input value: '' 	input count: 0 	value of a: ''
input value: '1' 	input count: 1 	value of a: '1'
input value: '2' 	input count: 1 	value of a: '2'
input value: '3' 	input count: 1 	value of a: '3'
input value: '' 	input count: 0 	value of a: '3'

As you can see, $input has no value in both the BEGIN and END blocks and a has the last value that $a was set to in the END block.

This rule is expressing the appropriate expectation that if you have pipelined parameters, you need to handle them in a PROCESS block. The rule violation has nothing to do with $input in the END block, only that you have failed to handle the pipeline variable in the appropriate block.

[brianary]

@JamesWTruher Yes, you can’t mix $input in multiple blocks, as I said, because it consumes the values.

function f1 {
    param ([parameter(ValueFromPipeline=$true)]$a)
    END     { "input value: '$input' `tinput count: $($input.count) `tvalue of a: '$a'" }
}

input value: '1 2 3'    input count: 3  value of a: '3'