> ## 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/PSDSCReturnCorrectTypesForDSCFunctions

> Return Correct Types For DSC Functions

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

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

<Note>
  tally disables this rule by default because Desired State Configuration resources are out
  of scope for Dockerfile `RUN` analysis. Re-enable it with
  `include = ["powershell/PSDSCReturnCorrectTypesForDSCFunctions"]` or by setting
  `rules.powershell.PSDSCReturnCorrectTypesForDSCFunctions.severity = "warning"` in `.tally.toml`.
</Note>

## Description

The functions in DSC resources have specific return objects.

For non-class based resources:

* `Set-TargetResource` must not return any value.
* `Test-TargetResource` must return a boolean.
* `Get-TargetResource` must return a hash table.

For class based resources:

* `Set` must not return any value.
* `Test` must return a boolean.
* `Get` must return an instance of the DSC class.

## How

Ensure that each function returns the correct type.

## Example 1

### Problematic code

```powershell theme={null}
function Get-TargetResource
{
    param
    (
        [parameter(Mandatory = $true)]
        [String]
        $Name
    )
    ...
}

function Set-TargetResource
{
    param
    (
        [parameter(Mandatory = $true)]
        [String]
        $Name
    )
    ...
}

function Test-TargetResource
{
    param
    (
        [parameter(Mandatory = $true)]
        [String]
        $Name
    )
    ...
}
```

### Correct code

```powershell theme={null}
function Get-TargetResource
{
    [OutputType([Hashtable])]
    param
    (
        [parameter(Mandatory = $true)]
        [String]
        $Name
    )
    ...
}

function Set-TargetResource
{
    param
    (
        [parameter(Mandatory = $true)]
        [String]
        $Name
    )
    ...
}

function Test-TargetResource
{
    [OutputType([System.Boolean])]
    param
    (
        [parameter(Mandatory = $true)]
        [String]
        $Name
    )
    ...
}
```

## Example 2

### Problematic code

```powershell theme={null}
[DscResource()]
class MyDSCResource
{
    [DscProperty(Key)]
    [string] $Name

    [String] Get()
    {
        ...
    }

    [String] Set()
    {
        ...
    }

    [bool] Test()
    {
        ...
    }
}
```

### Correct code

```powershell theme={null}
[DscResource()]
class MyDSCResource
{
    [DscProperty(Key)]
    [string] $Name

    [MyDSCResource] Get()
    {
        ...
    }

    [void] Set()
    {
        ...
    }

    [bool] Test()
    {
        ...
    }
}
```

## Source

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