Variables defined with `Set-Variable` are not fully supported in the editor

[DmitrySokolov]

Issue Type: Bug

Set-Variable MY_CONST 1 -Option Constant

Write-Host "MY_CONST = $($MY_CONST)"

1. When cursor is on the fisrt MY_CONST, other $MY_CONST is not highlighted
2. When typing $MY_<crtl+space> there is no suggestion for $MY_CONST

Extension version: 2020.1.0
VS Code version: Code 1.41.1 (26076a4de974ead31f97692a0d32f90d735645c0, 2019-12-18T14:58:56.166Z)
OS version: Windows_NT x64 10.0.18363

[rjmholt]

Indeed using Set-Variable causes issues for PowerShell as well.

The ability to define a variable using a command is something particular to PowerShell and its dynamism.

There are simple cases, but in general it's impossible to analyse Set-Variable. For example:

$varName = 'y'
Set-Variable $x 1

$y

Or

$varName = Get-Content -Raw ./myVarName.txt
Set-Variable $varName 1

$y # Is this a reference of the variable defined above??

Or even better:

Set-Alias (Get-Content -Raw ./setVariableName.txt) Set-Variable

# Is this Set-Variable??
AssignVariable y 1

# Has $y been assigned??
$y 

(This last one is actually unaccounted for in PowerShell's own code, so I highly recommend against it.)

So given the pitfalls of using Set-Variable (it will cause the PowerShell compiler to deoptimise code, since it can no longer guarantee things about variables), and the general impossibility of analysing scripts that use any of the variable cmdlets, our ability to resolve references to variables affected by them is to basically "do what we can and hope for simple cases".

There's also the other argument that Set-Variable isn't really a variable reference; there's no variable on that line, because it's just a command taking a string. From a purely syntactic perspective, there are no variables there.

However, with all of this being said, I think that editors should try to be helpful where they can be. In that respect this is a bit like #261 (comment). So ideally I'd like the PowerShell extension to have this one day. But it's not currently on our agenda, as we drive toward other improvements in the extension's architecture.