Why 'advanced functions' should be your PowerShell default

Did you know that simple functions could create hidden pitfalls? Advanced functions, created by adding [CmdletBinding()] and param(), ensure full PowerShell compatibility. These functions can utilize helpful features like $PSDefaultParameterValues, enhancing reliability and avoiding debugging issues.

Let advanced functions be your PowerShell default

Unknown to many, PowerShell supports two different types of function:

• simple functions and 
• advanced functions.

Only advanced functions support all PowerShell features, and if there are no specific reasons why you explicitly want an old simple function, as a safety rule, you should always ensure that all of your functions are advanced functions.

The simplest way to ensure this is to add this to all of your functions:

[CmdletBinding()]

param() 

If you want to define parameters, add them to the param() block. If you want to define special cmdlet features, add them to [CmdletBinding()]. For example, try this to add the ‑WhatIf and ‑Confirm parameters:

[CmdletBinding(SupportsShouldProcess)]

param() 

From a user perspective, you can always verify that a function is indeed an "advanced function": It supports all the common parameters (i.e. ‑Verbose, ‑ErrorAction) whereas "simple functions" only support the parameters that you defined yourself.

Extra Tip: Simple functions lack many features that may not be evident at first. For example, they are not compatible with $PSDefaultParameterValues. Avoid simple functions so you don’t run in hard-to-debug edge case problems due to not supported internal functionality.

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