How to test for existence of a script-scoped variable in PowerShell?
- by Damian Powell
Is it possible to test for the existence of a script-scoped variable in PowerShell?
I've been using the PowerShell Community Extensions (PSCX) but I've noticed that if you import the module while Set-PSDebug -Strict is set, an error is produced:
The variable '$SCRIPT:helpCache' cannot be retrieved because it has not been set.
At C:\Users\...\Modules\Pscx\Modules\GetHelp\Pscx.GetHelp.psm1:5 char:24
While investigating how I might fix this, I found this piece of code in Pscx.GetHelp.psm1:
#requires -version 2.0
param([string[]]$PreCacheList)
if ((!$SCRIPT:helpCache) -or $RefreshCache) {
$SCRIPT:helpCache = @{}
}
This is pretty straight forward code; if the cache doesn't exist or needs to be refreshed, create a new, empty cache. The problem is that calling $SCRIPT:helpCache while Set-PSDebug -Strict is in force casues the error because the variable hasn't been defined yet.
Ideally, we could use a Test-Variable cmdlet but such a thing doesn't exist! I thought about looking in the variable: provider but I don't know how to determine the scope of a variable.
So my question is: how can I test for the existence of a variable while Set-PSDebug -Strict is in force, without causing an error?
