Wrapper function with same name as command in Powershell?

Question

I am making attempting to fix an app which has recently broken the ls command, using a Powershell wrapper script. My wrapper must have the same name as the command it is invoking, so I'm using invoke-command to call the original command.

# yarn broke 'ls'
function yarn() {
    $modifiedArgs = @()
    foreach ( $arg in $args ) {
        if ( $arg -cmatch '^ls$' ) {
            $arg = 'list'
        }
        $modifiedArgs = $modifiedArgs + $arg
    }
    invoke-command yarn -ArgumentList @modifiedArgs
}

However invoke-command fails with

Invoke-Command : Parameter set cannot be resolved using the specified named parameters

How can I run the original command with the modified parameters?

Edit: I've also tried -ArgumentList (,$modifiedArgs) per Passing array to another script with Invoke-Command and I still get the same error.

Edit: Looks like invoke-command is remoting only. I've also tried Invoke-Expression "& yarn $modifiedArgs" but that runs the function itself.

You want to write a "proxy function". There is some good information on this at Microsoft's Scripting Guy column, Microsoft TechNet's Script Center Repository, and PowerShell With a Purpose (Windows ITPro). If you want more info, this Google search may be useful. — Jeff Zeitlin
– Jeff Zeitlin, Commented Sep 28, 2017 at 13:02
Thanks @JeffZeitlin but this is a binary command: I'm not wrapping other powershell. Even if it was, extracting the code of the original function per the Scripting Guy column seems like using a sledgehammer to crack a walnut here. — mikemaccana
– mikemaccana, Commented Sep 28, 2017 at 13:06

mikemaccana · Accepted Answer · 2017-09-29 12:40:33Z

1

I belive you can get around needing to specify the full path to the command if you scope the wrapper function to Private:

# yarn broke 'ls'
function Private:yarn() {
    $modifiedArgs = @()
    foreach ( $arg in $args ) {
        if ( $arg -cmatch '^ls$' ) {
            $arg = 'list'
        }
        $modifiedArgs += $arg
    }
    & yarn $modifiedArgs
}

This will prevent the function from being visible to child scopes, and it will revert back to using the application.

edited Sep 29, 2017 at 12:40

mikemaccana

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answered Sep 28, 2017 at 14:35

mjolinor

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Comments

mikemaccana · Accepted Answer · 2017-09-28 13:02:23Z

1

Per the powershell docs the & operator works:

# yarn broke 'ls'
function yarn() {
    $modifiedArgs = @()
    foreach ( $arg in $args ) {
        if ( $arg -cmatch '^ls$' ) {
            $arg = 'list'
        }
        $modifiedArgs += $arg
    }
    & 'C:\Program Files (x86)\Yarn\bin\yarn.cmd' $modifiedArgs
}

Still happy to accept other answers that don't involve specifying the command path explicitly.

answered Sep 28, 2017 at 13:02

mikemaccana

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1 Comment

user4003407 Over a year ago

& (gcm yarn -type application -totalcount 1)

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