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Add UseSingleValueFromPipelineParameter Rule #2119

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Add UseSingleValueFromPipelineParameter Rule #2119

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liamjpeters
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@liamjpeters liamjpeters commented Aug 9, 2025 •
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PR Summary

Adds a new rule, UseSingleValueFromPipelineParameter, which flags when multiple parameters in the same parameter set have ValueFromPipeline set to true.

When running something like:

function Test-ValueFromPipeline {
    [CmdletBinding()]
    param (
        [Parameter(ValueFromPipeline)]
        [string]
        $Parameter1,
        [Parameter(ValueFromPipeline)]
        [string]
        $Parameter2
    )
    process {
        "Parameter1: $Parameter1!"
        "Parameter2: $Parameter2!"
    }
}

"Value1" | Test-ValueFromPipeline

I don't get any kind of error or warning, which I was surprised by.

Consistent behaviour across both 5.1 and 7.4.11.

Multiple parameters accepting pipeline input by value doesn't make sense (to me at least - maybe I'm missing a use-case?).

The above outputs:

Parameter1: Value1!
Parameter2: Value1!

Both parameters get the pipeline input bound.

Parameter [Parameter2] PIPELINE INPUT ValueFromPipeline NO COERCION
BIND arg [Value1] to parameter [Parameter2]
    Executing DATA GENERATION metadata: [System.Management.Automation.ArgumentTypeConverterAttribute]
        result returned from DATA GENERATION: Value1
    BIND arg [Value1] to param [Parameter2] SUCCESSFUL
Parameter [Parameter1] PIPELINE INPUT ValueFromPipeline NO COERCION
BIND arg [Value1] to parameter [Parameter1]
    Executing DATA GENERATION metadata: [System.Management.Automation.ArgumentTypeConverterAttribute]
        result returned from DATA GENERATION: Value1
    BIND arg [Value1] to param [Parameter1] SUCCESSFUL

PR Checklist

@liamjpeters
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Bodging a built version of this into VSCode, I think it makes sense to flag each parameter attributes so they all get a yellow squiggly. That said, if there's a way to emit a single DiagnosticRecord that has multiple extents, I'm happy to change it.

image

@liamjpeters liamjpeters changed the title Use single value from pipeline parameter Add UseSingleValueFromPipelineParameter Rule Aug 18, 2025
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@sdwheeler sdwheeler Awaiting requested review from sdwheeler sdwheeler is a code owner

@michaeltlombardi michaeltlombardi Awaiting requested review from michaeltlombardi michaeltlombardi is a code owner

@andyleejordan andyleejordan Awaiting requested review from andyleejordan andyleejordan is a code owner

@bergmeister bergmeister Awaiting requested review from bergmeister bergmeister is a code owner

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