Powershell Removing Quotes Argument - powershell

Question

I'm using Start-Process to start another instance of Powershell as an administrator but when I try to pass the argument list, whether as a variable or as a plain string, Powershell removes the quotes. Below is the command I'm using:
$argu = '-noexit "C:\Program Files (x86)\Microsoft Visual Studio\2017\BuildTools\VC\Auxiliary\Build\vcvars64.bat"';
powershell Start-Process -Verb RunAs -FilePath powershell -ArgumentList $argu
This is the error I get:
x86 : The term 'x86' is not recognized as the name of a cmdlet, function, script file, or operable program. Check the spelling of the name, or if a path was included,
verify that the path is correct and try again.
At line:1 char:88
+ ... Program Files (x86)\Microsoft Visual Studio\2017\BuildTools\VC\Auxiliary\Build\v ...
+ ~~~
+ CategoryInfo : ObjectNotFound: (x86:String) [], CommandNotFoundException
+ FullyQualifiedErrorId : CommandNotFoundException
Thank you in advance for any help.
Update:
$argu = '''-noexit ""C:\Program Files (x86)\Microsoft Visual Studio\2017\BuildTools\VC\Auxiliary\Build\vcvars64.bat""''';
powershell Start-Process -Verb RunAs -FilePath powershell -ArgumentList $argu
This almost fixes it but now I'm getting the error above in the second window instead of the first.

Answer 1

(A) From inside PowerShell:
$argu = '-noexit -command & \"C:\Program Files (x86)\Microsoft Visual Studio\2017\BuildTools\VC\Auxiliary\Build\vcvars64.bat\"'
Start-Process -Verb RunAs -FilePath powershell -ArgumentList $argu
Note: I'm not calling Start-Process via powershell.exe, as there is generally no need for that.
The embedded " are \-escaped, which is what PowerShell requires when you call its CLI (perhaps surprisingly, given that PowerShell-internally it is ` that acts as the escape character).
That said given that the " are embedded inside '...' here, they shouldn't require extra escaping - see below.
The file path to execute is prefixed with call operator &, because you need it in order to execute files that are specified in quoted form.
Note that I've added -Command, which is not strictly necessary in Windows PowerShell, but would be if you ran your command from PowerShell Core (which now defaults to -File).
Alternatively, you could also specify your arguments individually, as part of an array, which is arguably the cleaner solution:
$argu = '-noexit', '-command', '&', 'de',
'\"C:\Program Files (x86)\Microsoft Visual Studio\2017\BuildTools\VC\Auxiliary\Build\vcvars64.bat\"'
Start-Process -Verb RunAs -FilePath powershell -ArgumentList $argu
Sadly, even in this case you need the extra, embedded quoting for arguments that contain spaces, which is a known Start-Process problem being tracked on GitHub.
PowerShell's handling of quoting when calling external programs is generally problematic; the current issues are summarized in this GitHub issue.
(B) From outside PowerShell (cmd.exe, a custom File Explorer context menu):
powershell -command Start-Process -Verb RunAs -FilePath powershell -ArgumentList '-noexit -command . ''C:\Program Files (x86)\Microsoft Visual Studio\2017\BuildTools\VC\Auxiliary\Build\vcvars64.bat'''
single-quoting is now employed (with nested single quotes escaped as ''), because double-quoting would substantially complicate the escaping.
. is used instead of & to execute the .bat file, which avoids a problem with how the & is parsed; while . generally serves a different purpose than &, the two operators behave the same when calling external programs.
If you also want to set the working directory for the PowerShell session that ultimately opens elevated, you need to incorporate an explicit Set-Location (cd) call into the command string, because Start-Process -Verb RunAs always defaults to the SYSTEM32 folder (even the -WorkingDirectory parameter doesn't help in that case).
For that to work safely, however, you must quote the directory path using double-quoting, given that file names may contain single quotes; with %V as the directory path (which File Explorer supplies to commands invoked via custom context menus), the properly escaped Set-Location call looks like this (I wish I were kidding):
Set-Location \"\"\"%V%\"\"\"
Integrated into the full command (using Set-Location's built-in alias cd for brevity):
powershell -command Start-Process -Verb RunAs -FilePath powershell -ArgumentList '-noexit -command cd \"\"\"%V%\"\"\"; . ''C:\Program Files (x86)\Microsoft Visual Studio\2017\BuildTools\VC\Auxiliary\Build\vcvars64.bat'''
As an aside: PowerShell Core now has a -WorkingDirectory (-wd) CLI parameter that allows you to control the startup directory more robustly (pwsh -wd "c:\path\to\dir" ...); in fact, it was precisely the File Explorer custom context-menu use case that prompted the introduction of this parameter.