> ## Documentation Index
> Fetch the complete documentation index at: https://tally.wharflab.com/llms.txt
> Use this file to discover all available pages before exploring further.

# powershell/PSAvoidNullOrEmptyHelpMessageAttribute

> Avoid using null or empty HelpMessage parameter attribute.

`powershell/PSAvoidNullOrEmptyHelpMessageAttribute` is a PSScriptAnalyzer diagnostic emitted by tally for PowerShell snippets embedded in Dockerfiles.

| Property | Value             |
| -------- | ----------------- |
| Severity | Warning           |
| Category | PSScriptAnalyzer  |
| Default  | Disabled in tally |
| Auto-fix | No                |

<Note>
  tally disables this rule by default for Dockerfile `RUN` snippets because a `RUN` executes
  statements inline rather than defining cmdlets, parameters, or modules with external callers. Re-enable it with
  `include = ["powershell/PSAvoidNullOrEmptyHelpMessageAttribute"]` or by setting
  `rules.powershell.PSAvoidNullOrEmptyHelpMessageAttribute.severity = "warning"` in `.tally.toml`.
</Note>

## Description

The value of the `HelpMessage` attribute should not be an empty string or a null value as this
causes PowerShell's interpreter to throw an error when executing the function or cmdlet.

## How

Specify a value for the `HelpMessage` attribute.

## Examples

### Problematic code

```powershell theme={null}
Function BadFuncEmptyHelpMessageEmpty
{
    Param(
        [Parameter(HelpMessage='')]
        [String]
        $Param
    )

    $Param
}

Function BadFuncEmptyHelpMessageNull
{
    Param(
        [Parameter(HelpMessage=$null)]
        [String]
        $Param
    )

    $Param
}

Function BadFuncEmptyHelpMessageNoAssignment
{
    Param(
        [Parameter(HelpMessage)]
        [String]
        $Param
    )

    $Param
}
```

### Correct code

```powershell theme={null}
Function GoodFuncHelpMessage
{
    Param(
        [Parameter(HelpMessage='This is helpful')]
        [String]
        $Param
    )

    $Param
}
```

## Source

This rule documentation is adapted from Microsoft's PSScriptAnalyzer documentation for
[AvoidNullOrEmptyHelpMessageAttribute](https://github.com/MicrosoftDocs/PowerShell-Docs-Modules/blob/main/reference/docs-conceptual/PSScriptAnalyzer/Rules/AvoidNullOrEmptyHelpMessageAttribute.md),
licensed under [CC BY 4.0](https://creativecommons.org/licenses/by/4.0/).