New Rule: Calling Start-Process without checking ExitCode #1062

Summary of the new feature
I recently got burned by a library not handling the exit code for Microsoft.PowerShell.Management\Start-Process.

This could be broken into two rules:

• Always assign Start-Process to a local variable, and check the result. Caveat: How would this work if invoked from Start-Job and deliberately intended to be asynchronous?

Proposed technical implementation details (optional)

1. Find calls to Microsoft.PowerShell.Management\Start-Process
   There are several ways this could be called:

Arguments not known at caller. No local way to detect $args sets the -Wait and -NoNewWindow switches on

function Do
{
param(
 [hashtable]$StartProcess_params
)
  Microsoft.PowerShell.Management\Start-Process @StartProcess_params
}

Trivial case: Direct arguments

Microsoft.PowerShell.Management\Start-Process -FilePath "cmd.exe" -ArgumentList "/C" -Wait -NoNewWindow

Middle case: arguments constructed in same scope - I believe this is called $script scope

$StartProcess_params = @{
  FilePath = "cmd.exe"
  ArgumentList = "/C"
  RedirectStandardError = $tempErrorFile
  RedirectStandardOutput = $tempOutputFile
  NoNewWindow = $true
  Wait = $true
}
Microsoft.PowerShell.Management\Start-Process @StartProcess_params

Using Start-Job

Start-Job -Name DoSomething -ScriptBlock {
    & cmd.exe /C
    Write-Output $LASTEXITCODE
}
#Do other stuff here
Get-Job -Name DoSomething | Wait-Job | Receive-Job

A clear and concise description of what you want to happen.
Flag as warnings with suggestion to assign call to a PS variable, e.g.:
Microsoft.PowerShell.Management\Start-Process @StartProcess_params
would become:

$process = Microsoft.PowerShell.Management\Start-Process @StartProcess_params
if (-not $process.ExitCode)
{
  Write-Error $(Microsoft.PowerShell.Management\Get-Content $tempErrorFile
}

Alternatively, if the user truly wishes to suppress the result, the UI could offer a "No, I really don't care and want to explicitly say so" command, which would re-write the code to be:

$(Microsoft.PowerShell.Management\Start-Process @StartProcess_params) | Out-Null

or

[void]Microsoft.PowerShell.Management\Start-Process @StartProcess_params

According to StackOverflow, Out-Null adds a 60% overhead and therefore is slower than [void], so we should probably suggest [void]Microsoft.PowerShell.Management\Start-Process @StartProcess_params

What is the latest version of PSScriptAnalyzer at the point of writing
1.17.1