How to make Invoke-Command return empty array instead of null when run script block

Question

I am creating a function and sometimes, it will return a empty array as there is not result. This function may need to run with Invoke-Command for some scenario, such as run on a remote PC and etc.

But what i found that, when my function run under Invoke-Command with script block, it cannot return empty array, but just null.

So I have a try and find that, the Invoke-Command seems to not able to return empty array even though I do that explicitly.

For exmaple:

> $foo = @()
> $foo.GetType()

IsPublic IsSerial Name                                     BaseType                                          
-------- -------- ----                                     --------                                          
True     True     Object[]                                 System.Array 

> $foo = Invoke-Command -ScriptBlock { @() }
> $foo.GetType()
You cannot call a method on a null-valued expression.
At line:1 char:1
+ $foo.GetType()
+ ~~~~~~~~~~~~~~
    + CategoryInfo          : InvalidOperation: (:) [], RuntimeException
    + FullyQualifiedErrorId : InvokeMethodOnNull

> $foo -eq $null
True

So how can I return empty array in this scenario? Any mistake here? Or any trick here?

score 3 · Accepted Answer · answered Jul 24 '17 at 08:43

3

Just prepend the returning value with comma , (array construction operator). Then the return value will not get flattened into $null:

$foo = Invoke-Command -ScriptBlock { ,@() }

answered Jul 24 '17 at 08:43

Mikhail Tumashenko

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Can anyone comment on why this is necessary for Invoke-Command but not a typical function return call? – aggieNick02 Oct 11 '17 at 18:23
As I know powershell functions behave the same - the empty array will get flattened on return. – Mikhail Tumashenko Oct 25 '17 at 14:46

How to make Invoke-Command return empty array instead of null when run script block

1 Answers1