JoinItem.ps1

#requires -Version 5.0
using namespace System.Management.Automation
using Namespace System.Collections
using Namespace System.Collections.Generic


<#
.SYNOPSIS
    Combine items from the pipeline into a string, optionally adding single or double quotes

.DESCRIPTION
    The Join-Item command joins items from the pipeline into a string, optionally adding single or double quotes 
    and inserts a delimiter between the items

.EXAMPLE
1..10 | Join-Item -DoubleQuote
This example shows how to join numbers with double quotes

output: "1","2","3","4","5","6","7","8","9","10"

.EXAMPLE
1..10 | Join-Item -Delimiter ';'
This example shows how to join numbers with a non default Delimiter

output: 1;2;3;4;5;6;7;8;9;10


.EXAMPLE

1..10 | Join-Item -Delimiter ', ' -Quote

This example shows how to join numbers with a Delimiter ', ' with the items quoted

output: '1', '2', '3', '4', '5', '6', '7', '8', '9', '10'

.EXAMPLE
Get-ChildItem | Join-Item -Property Name -Quote
This example demonstrates how to join the value of a named property of the pipeline objects into
a quoted, comma separated, string

output: 'file1.ps1','file2.ps1','file3.ps1'
#>
function Join-Item {
    [Alias('ji')]
    [CmdletBinding(DefaultParameterSetName = 'Default')]
    [OutputType([string])]
    param(                        
        [Parameter(Position = 0)]
        [ArgumentCompleter([JoinItemCompleter])]
        [string] $Delimiter = ',',        
        [Parameter(Position = 1)]
        [string] $PropertyName,
        [Parameter(ParameterSetName = 'Quote')]
        [switch] $Quote,
        [Parameter(ParameterSetName = 'DoubleQuote')]
        [switch] $DoubleQuote,
        [Parameter(ValueFromPipeline, Mandatory)]
        [PSObject[]] $InputObject
    )
    begin {
        Set-StrictMode -Version Latest
        $inputObjects = [List[PSObject]]::new(100)    
    }
    process {        
        $inputObjects.AddRange($InputObject)        
    }
    end {
        $isPropertyName = $PSBoundParameters.ContainsKey('PropertyName')        
        for ($i = 0; $i -lt $inputObjects.Count; ++$i) {
            if ($isPropertyName) {
                $value = $inputObjects[$i].$PropertyName.ToString()
            }
            else {
                $value = $inputObjects[$i].ToString()
            }
            if ($Quote) {
                $value = "'$value'"
            }
            elseif ($DoubleQuote) {
                $value = "`"$value`""
            }            
            $inputObjects[$i] = $value            
        }
        $str = $InputObjects -join $Delimiter
        $PSCmdlet.WriteObject($str)                        
    }
}

class JoinItemCompleter : IArgumentCompleter {
    [IEnumerable[CompletionResult]] CompleteArgument(
        [string] $CommandName,
        [string] $ParameterName,
        [string] $wordToComplete,
        [Language.CommandAst] $commandAst,
        [IDictionary] $fakeBoundParameters
    ) {
        $result = [List[CompletionResult]]::new(5)        
        $this.AddResultIf(', ', 'Comma-Space', $wordToComplete, $result)
        $this.AddResultIf(';', 'Semi-Colon', $wordToComplete, $result)
        $this.AddResultIf('; ', 'Semi-Colon-Space', $wordToComplete, $result)
        $this.AddResultIf('`r`n', 'Newline', $wordToComplete, $result)        
        $this.AddResultIf(',', 'Comma', $wordToComplete, $result)        
        $this.AddResultIf('-', 'Dash', $wordToComplete, $result)
        $this.AddResultIf(' ', 'Space', $wordToComplete, $result)

        return $result
    }
    [void] AddResultIf([string] $complete, [string] $description, [string] $wordToComplete, [List[CompletionResult]] $result) {
        if ($complete.StartsWith($wordToComplete, [System.StringComparison]::OrdinalIgnoreCase)) {
            $result.Add([CompletionResult]::new("`"$complete`"", $description, [CompletionResultType]::ParameterValue, "'$complete' - $description"))
        }
    }
}

<#
Describe 'Join-Item tests' {
    It 'Should default join with comma' {
        1..4 | Join-Item  | Should BE '1,2,3,4'
    }

    It 'can double quote with default delimiter' {
        1..4 | Join-Item -DoubleQuote | Should BE '"1","2","3","4"'
    }

    It 'can quote with default delimiter' {
        1..4 | Join-Item -Quote  | Should BE "'1','2','3','4'"
    }

    It 'Should join with Delimiter' {
        1..4 | Join-Item -Delimiter ', '  | Should BE '1, 2, 3, 4'
    }

    It 'Should join Property with Delimiter' {
        @(
            @{Name = 'Ken'}
            @{Name = 'Barbie'}
            @{Name = 'Donald'}
        ) | Join-Item -Delimiter ', ' -Property Name -DoubleQuote | Should be '"Ken", "Barbie", "Donald"'
    }
}
#>