Powershell Profile to append parameters to a certain command - powershell

Question

I have a certain command that I want to be able to append a parameter to as a powershell profile function. Though I'm not quite sure the best way to be able to capture each time this command is run, any insight would be helpful.
Command: terraform plan
Each time a plan is run I want to be able to check the parameters and see if -lock=true is passed in and if not then append -lock=false to it. Is there a suitable way to capture when this command is run, without just creating a whole new function that builds that command? So far the only way I've seen to capture commands is with Start-Transcript but that doesn't quite get me to where I need.

Answer 1

The simplest approach is to create a wrapper function that analyzes its arguments and adds -lock=false as needed before calling the terraform utility.
function terraform {
$passThruArgs = $args
if (-not ($passThruArgs -match '^-lock=')) { $passThruArgs += '-lock=false'}
& (Get-Command -Type Application terraform) $passThruArgs
}
The above uses the same name as the utility, effectively shadowing the latter, as is your intent.
However, I would caution against using the same name for the wrapper function, as it can make it hard to understand what's going on.
Also, if defined globally via $PROFILE or interactively, any unsuspecting code run in the same session will call the wrapper function, unless an explicit path or the shown Get-Command technique is used.

Answer 2

Not to take away from the other answer posted, but to offer an alternative solution here's my take:
$Global:CMDLETCounter = 0
$ExecutionContext.InvokeCommand.PreCommandLookupAction = {
Param($CommandName, $CommandLookupEvents)
if ($CommandName -eq 'terraform' -and $Global:CMDLETCounter -eq 0)
{
$Global:CMDLETCounter++
$CommandLookupEvents.CommandScriptBlock = {
if ($Global:CMDLETCounter -eq 1)
{
if (-not ($args -match ($newArg = '-lock=')))
{
$args += "${newArg}true"
}
}
& "terraform" #args
$Global:CMDLETCounter--
}
}
}
You can make use of the $ExecutionContext automatic variable to tap into PowerShells parser and insert your own logic for a specific expression. In your case, youd be using terraform which the command input will be parsed for each token and checked against -lock= in the existing arguments. If not found, append -lock=true to the current arguments and execute the command again.
The counter you see ($Global:CMDLETCounter) is to prevent an endless loop as it would just recursively call itself without there being something to halt it.