Private/Get-Parameter.ps1

# Borrowed from http://poshcode.org/5929 with a minor tweak for validateset - thanks all!
Function Get-Parameter {
   #.Synopsis
   # Enumerates the parameters of one or more commands
   #.Description
   # Lists all the parameters of a command, by ParameterSet, including their aliases, type, etc.
   #
   # By default, formats the output to tables grouped by command and parameter set
   #.Example
   # Get-Command Select-Xml | Get-Parameter
   #.Example
   # Get-Parameter Select-Xml
   [CmdletBinding(DefaultParameterSetName="ParameterName")]
   param(
      # The name of the command to get parameters for
      [Parameter(Position = 1, Mandatory = $true, ValueFromPipelineByPropertyName = $true)]
      [Alias("Name")]
      [string[]]$CommandName,

      # The parameter name to filter by (allows Wilcards)
      [Parameter(Position = 2, ValueFromPipelineByPropertyName=$true, ParameterSetName="FilterNames")]
      [string[]]$ParameterName = "*",

      # The ParameterSet name to filter by (allows wildcards)
      [Parameter(ValueFromPipelineByPropertyName=$true, ParameterSetName="FilterSets")]
      [string[]]$SetName = "*",

      # The name of the module which contains the command (this is for scoping)
      [Parameter(ValueFromPipelineByPropertyName = $true)]
      $ModuleName,

      # Skip testing for Provider parameters (will be much faster)
      [Switch]$SkipProviderParameters,

      # Forces including the CommonParameters in the output
      [switch]$Force
   )

   begin {
      $PropertySet = @( "Name",
         @{n="Position";e={if($_.Position -lt 0){"Named"}else{$_.Position}}},
         "Aliases", 
         @{n="Short";e={$_.Name}},
         @{n="Type";e={$_.ParameterType.Name}}, 
         @{n="ParameterSet";e={$paramset}},
         @{n="Command";e={$command}},
         @{n="Mandatory";e={$_.IsMandatory}},
         @{n="Provider";e={$_.DynamicProvider}},
         @{n="ValueFromPipeline";e={$_.ValueFromPipeline}},
         @{n="ValueFromPipelineByPropertyName";e={$_.ValueFromPipelineByPropertyName}},
         "ValidateSetValues" # This is a bit specific and not always applicable, but need it for this project....
      )
      function Join-Object {
         Param(
           [Parameter(Position=0)]
           $First,

           [Parameter(ValueFromPipeline=$true,Position=1)]
           $Second
         )
         begin {
           [string[]] $p1 = $First | Get-Member -MemberType Properties | Select-Object -ExpandProperty Name
         }
         process {
           $Output = $First | Select-Object $p1
           foreach ($p in $Second | Get-Member -MemberType Properties | Where-Object {$p1 -notcontains $_.Name} | Select-Object -ExpandProperty Name) {
              Add-Member -InputObject $Output -MemberType NoteProperty -Name $p -Value $Second."$p"
           }
           $Output
         }
      }

      function Add-Parameters {
         [CmdletBinding()]
         param(
            [Parameter(Position=0)]
            [Hashtable]$Parameters,

            [Parameter(Position=1)]
            [System.Management.Automation.ParameterMetadata[]]$MoreParameters
         )

         foreach ($p in $MoreParameters | Where-Object { !$Parameters.ContainsKey($_.Name) } ) {
            Write-Debug ("INITIALLY: " + $p.Name)
            $Parameters.($p.Name) = $p | Select-Object *
         }

         [Array]$Dynamic = $MoreParameters | Where-Object { $_.IsDynamic }
         if ($dynamic) {
            foreach ($d in $dynamic) {
               if (Get-Member -InputObject $Parameters.($d.Name) -Name DynamicProvider) {
                  Write-Debug ("ADD:" + $d.Name + " " + $provider.Name)
                  $Parameters.($d.Name).DynamicProvider += $provider.Name
               } else {
                  Write-Debug ("CREATE:" + $d.Name + " " + $provider.Name)
                  $Parameters.($d.Name) = $Parameters.($d.Name) | Select-Object *, @{ n="DynamicProvider";e={ @($provider.Name) } }
               }
            } 
         }
      }
   }

   process {
      foreach ($cmd in $CommandName) {
         if ($ModuleName) {$cmd = "$ModuleName\$cmd"}
         Write-Verbose "Searching for $cmd"
         $commands = @(Get-Command $cmd)

         foreach ($command in $commands) {
            Write-Verbose "Searching for $command"
            # resolve aliases (an alias can point to another alias)
            while ($command.CommandType -eq "Alias") {
              $command = @(Get-Command ($command.definition))[0]
            }
            if (-not $command) {continue}

            Write-Verbose "Get-Parameters for $($Command.Source)\$($Command.Name)"

            $Parameters = @{}

            ## We need to detect provider parameters ...
            $NoProviderParameters = !$SkipProviderParameters
            ## Shortcut: assume only the core commands get Provider dynamic parameters
            if(!$SkipProviderParameters -and $Command.Source -eq "Microsoft.PowerShell.Management") {
               ## The best I can do is to validate that the command has a parameter which could accept a string path
               foreach($param in $Command.Parameters.Values) {
                  if(([String[]],[String] -contains $param.ParameterType) -and ($param.ParameterSets.Values | Where-Object { $_.Position -ge 0 })) {
                     $NoProviderParameters = $false
                     break
                  }
               }
            }

            if($NoProviderParameters) {
               if($Command.Parameters) {
                  Add-Parameters $Parameters $Command.Parameters.Values
               }
            } else {
               foreach ($provider in Get-PSProvider) {
                  if($provider.Drives.Length -gt 0) {
                     $drive = Get-Location -PSProvider $Provider.Name
                  } else {
                     $drive = "{0}\{1}::\" -f $provider.ModuleName, $provider.Name
                  }
                  Write-Verbose ("Get-Command $command -Args $drive | Select -Expand Parameters")

                  try {
                     $MoreParameters = (Get-Command $command -Args $drive).Parameters.Values
                  } catch {}
       
                  if($MoreParameters.Length -gt 0) {
                     Add-Parameters $Parameters $MoreParameters
                  }
               }
               # If for some reason none of the drive paths worked, just use the default parameters
               if($Parameters.Length -eq 0) {
                  if($Command.Parameters) {
                     Add-Parameters $Parameters $Command.Parameters.Values
                  }
               }
            }

            ## Calculate the shortest distinct parameter name -- do this BEFORE removing the common parameters or else.
            $Aliases = $Parameters.Values | Select-Object -ExpandProperty Aliases  ## Get defined aliases
            $ParameterNames = $Parameters.Keys + $Aliases
            foreach ($p in $($Parameters.Keys)) {
               $short = "^"
               $aliases = @($p) + @($Parameters.$p.Aliases) | Sort-Object { $_.Length }
               $shortest = "^" + @($aliases)[0]

               foreach($name in $aliases) {
                  $short = "^"
                  foreach ($char in [char[]]$name) {         
                     $short += $char
                     $mCount = ($ParameterNames -match $short).Count
                     if ($mCount -eq 1 ) {
                        if($short.Length -lt $shortest.Length) {
                           $shortest = $short
                        }
                        break
                     }
                  }
               }
               if($shortest.Length -lt @($aliases)[0].Length +1){
                  # Overwrite the Aliases with this new value
                  $Parameters.$p = $Parameters.$p | Add-Member NoteProperty Aliases ($Parameters.$p.Aliases + @("$($shortest.SubString(1))*")) -Force -Passthru
               }

               # ValidateSet...
               $Parameters.$p = $Parameters.$p | Add-Member NoteProperty ValidateSetValues ($Parameters.$p.Attributes | Where-Object {$_.TypeId.name -like 'ValidateSetAttribute'}).ValidValues -Force -Passthru

            }

            # Write-Verbose "Parameters: $($Parameters.Count)`n $($Parameters | ft | out-string)"
            $CommonParameters = [string[]][System.Management.Automation.Cmdlet]::CommonParameters

            foreach ($paramset in @($command.ParameterSets | Select-Object -ExpandProperty "Name")) {
               $paramset = $paramset | Add-Member -Name IsDefault -MemberType NoteProperty -Value ($paramset -eq $command.DefaultParameterSet) -PassThru
               foreach ($parameter in $Parameters.Keys | Sort-Object) {
                  # Write-Verbose "Parameter: $Parameter"
                  if (!$Force -and ($CommonParameters -contains $Parameter)) {continue}
                  if ($Parameters.$Parameter.ParameterSets.ContainsKey($paramset) -or $Parameters.$Parameter.ParameterSets.ContainsKey("__AllParameterSets")) {
                     if ($Parameters.$Parameter.ParameterSets.ContainsKey($paramset)) {
                        $output = Join-Object $Parameters.$Parameter $Parameters.$Parameter.ParameterSets.$paramSet 
                     } else {
                        $output = Join-Object $Parameters.$Parameter $Parameters.$Parameter.ParameterSets.__AllParameterSets
                     }

                     Write-Output $Output | Select-Object $PropertySet | ForEach-Object {
                           $null = $_.PSTypeNames.Insert(0,"System.Management.Automation.ParameterMetadata")
                           $null = $_.PSTypeNames.Insert(0,"System.Management.Automation.ParameterMetadataEx")
                           # Write-Verbose "$(($_.PSTypeNames.GetEnumerator()) -join ", ")"
                           $_
                        } |
                        Add-Member ScriptMethod ToString { $this.Name } -Force -Passthru |
                        Where-Object {$(foreach($pn in $ParameterName) {$_ -like $Pn}) -contains $true} |
                        Where-Object {$(foreach($sn in $SetName) {$_.ParameterSet -like $sn}) -contains $true}
                  }
               }
            }
         }
      }
   }
}