TabExpansion2

TabExpansion2
    [-inputScript] <String>
    [[-cursorColumn] <Int32>]
    [[-options] <Hashtable>]
    [<CommonParameters>]

TabExpansion2
    [-ast] <Ast>
    [-tokens] <Token[]>
    [-positionOfCursor] <IScriptPosition>
    [[-options] <Hashtable>]
    [<CommonParameters>]

TabExpansion2 is a built-in function that provides tab completion for user input. PowerShell calls this function when the user presses the Tab or Ctrl+Space key while typing a command. The function returns a list of possible completions for the current input.

TabExpansion2 isn't normally called directly by users. However, it can be useful for testing tab completion. To use TabExpansion2, you need to provide the current input script and the cursor position in the script. The function returns a CommandCompletion object that contains a list of possible completions for the current input. This input script can be a string or an abstract syntax tree (AST) that represents the script.

You can override the default behavior of TabExpansion2 by defining a custom function with the same name in your PowerShell session. This custom function can provide completions for custom commands or parameters. While it is possible to override TabExpansion2, it's not supported. You should create a custom function only if you have a specific need to customize the tab completion behavior.

This example shows the same results you would get by entering Format-Hex -<Tab> at the PowerShell command prompt. The TabExpansion2 function returns a CommandCompletion object that contains a list of possible completions for the - token.

TabExpansion2 -inputScript ($s = 'Format-Hex -') -cursorColumn $s.Length |
    Select-Object -ExpandProperty CompletionMatches

CompletionText ListItemText    ResultType ToolTip
-------------- ------------    ---------- -------
-Path          Path         ParameterName [string[]] Path
-LiteralPath   LiteralPath  ParameterName [string[]] LiteralPath
-InputObject   InputObject  ParameterName [psobject] InputObject
-Encoding      Encoding     ParameterName [Encoding] Encoding
-Count         Count        ParameterName [long] Count
-Offset        Offset       ParameterName [long] Offset

This example shows how to get tab completion for parameter values. In this example, we expect that Stage parameter has three possible values and that one of the values is Three. You can use this technique to test that tab completion for your function returns the expected results.

function Get-Data {
    param (
        [ValidateSet('One', 'Two', 'Three')]
        [string]$Stage
    )
    Write-Verbose "Retrieving data for stage $Stage"
}

$result = TabExpansion2 -inputScript ($line = 'Get-Data -Stage ') -cursorColumn $line.Length |
    Select-Object -ExpandProperty CompletionMatches
$result.Count -eq 3
$result.CompletionText -contains 'Three'

True
True

This cmdlet supports the common parameters: -Debug, -ErrorAction, -ErrorVariable, -InformationAction, -InformationVariable, -OutBuffer, -OutVariable, -PipelineVariable, -ProgressAction, -Verbose, -WarningAction, and -WarningVariable. For more information, see about_CommonParameters.