Functions and clean output contracts

The idea

A PowerShell function can emit multiple results even without a return statement. Any unassigned expression written to the success stream becomes part of its output. Return ends the current function or script block, but earlier output remains present. This differs from languages where one return expression is the only result channel, so inspect every statement that may emit a value.

Declare parameters with names, types, and validation appropriate to the contract. Use Write-Verbose for optional diagnostics instead of adding strings to the success stream of an object-producing function. Suppress unwanted method return values deliberately when necessary. A dependable function keeps its output shape consistent and lets callers decide whether to display, serialize, or further process the emitted records.

function Get-Double {
  [CmdletBinding()]
  param([Parameter(Mandatory)][int]$Value)
  Write-Verbose "Doubling a value"
  return $Value * 2
}
Get-Double -Value 4

8

The numeric result goes to the success stream. The diagnostic uses the verbose stream and is not included in the function’s ordinary captured result.