PipeScript

0.2.8

Transpilers/Syntax/WhereMethod.psx.ps1

<#
.SYNOPSIS
    Where Method
.DESCRIPTION
    Where-Object cannot simply run a method with parameters on each object.

    However, we can easily rewrite a Where-Object statement to do exactly that.
.EXAMPLE
    { Get-PipeScript | ? CouldPipeType([ScriptBlock]) } | Use-PipeScript
#>
[ValidateScript({
    $validating = $_
    if ($validating -isnot [Management.Automation.Language.CommandAst]) {
        return $false
    }
    if ($validating.CommandElements[0] -notin '?', 'Where', 'Where-Object') {
        return $false
    }
    if ($validating.CommandElements.Count -ne 3) {
        return $false
    }    
    if ($validating.CommandElements[2] -is [Management.Automation.Language.ParenExpressionAst]) {
        return $true
    }
    return $false
    
})]
param(
# The Where-Object Command AST.
[Parameter(Mandatory,ValueFromPipeline)]
[Management.Automation.Language.CommandAst]
$WhereCommandAst
)

process {
    # Use multiple assignment to split the command up
    $whereCommand, $whereMethodName, $whereMethod = $whereCommandAst.CommandElements
    # Fix psuedo-empty parenthesis to be properly empty.
    $whereMethod = $whereMethod -replace '\(`$(?>_|null)\)', '()'
    # Create the updated code (don't use Where-Object though, because this will be faster).
    $UpdatedWhereCommand = "& { process { if (`$_.${WhereMethodName}${WhereMethod}) { `$_ } } }"
    # Output the updated script block (and we're done).
    [scriptblock]::Create($UpdatedWhereCommand)
}