powershell - Why does the `using` scope work locally with Start-Job, but not Invoke-Command?

Question

Why doesn't PowerShell allow the use of the using scope when using Invoke-Command locally? According to the documentation, the using modifier can only be used on remote commands. To quote:

Beginning in PowerShell 3.0, you can use the Using scope modifier to identify a local variable in a remote command.

This behavior can be demonstrated when running Invoke-Command locally:

$myServerName = 'www.google.com'
Invoke-Command { ping $using:myServerName }

Which throws the following error:

A Using variable cannot be retrieved. A Using variable can be used only with Invoke-Command, Start-Job, or InlineScript in the script workflow. When it is used with Invoke-Command, the Using variable is valid only if the script block is invoked on a remote computer.

The error indicates that the remote use of the using modifier is only valid remotely, with Invoke-Command. So, if we try running the same thing using Start-Job, what happens?

$myServerName = 'www.google.com'
$j = Start-Job { ping $using:myServerName }
while( $j.State -eq 'Running' ){ Start-Sleep -s 1 }
Receive-Job $j

Which doesn't throw an error, and I get the output I expect:

 Pinging www.google.com [172.217.6.132] with 32 bytes of data:
 Reply from 172.217.6.132: bytes=32 time=20ms TTL=56
 Reply from 172.217.6.132: bytes=32 time=19ms TTL=56
 Reply from 172.217.6.132: bytes=32 time=19ms TTL=56
 Reply from 172.217.6.132: bytes=32 time=19ms TTL=56

---

Why does the documentation state that the using scope modifier only works remotely when it can be clearly used in local contexts as well? And similarly, if it works in the context of a local Start-Job, what stops it from working with a local Invoke-Command?

Answer 1

This is true when using "using" because the definition of using states,

Beginning in PowerShell 3.0, you can use the Using scope modifier to identify a local variable in a remote command

Anytime you use the $using, you have to provide -ComputerName or -Session arguments whether the target server is localhost or remote.

Ex.

$myServerName = 'www.google.com'
Invoke-Command { ping $using:myServerName }
### BIG ERROR.

$myServerName = 'www.google.com'
Invoke-Command { ping $using:myServerName } -computername $env:COMPUTERNAME
### Ping response.

$myServerName = 'www.google.com'
Invoke-Command { ping $myServerName }
### Ping Reponse.

$using: is only supported in a few, specific contexts, which have one thing in common: code that is being run outside the current runspace - all other contexts neither require nor support it. (@mklement0)

[Invoke-Command, Start-Job, and InlineScript are known contexts which support the use of $using: to pass variables in current local session.]

Documentation on where you can use $using