PowerShell script not zipping correct files

Pass the files as full paths to the Zip function, using their .FullName property (PSv3+ syntax):

Zip C:\Users\Admin\Desktop\TEST.zip $Files.FullName

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The problem is that, in Windows PowerShell, the [System.IO.FileInfo] instances returned by Get-ChildItem situationally^[1] stringify to their file names only, which is what happened in your case, so your Zip function then interpreted the $toBeZipped values as relative to the current location, which is C:\Program Files\7-Zip at that point.

That said, it’s better not to use Set-Location in your function altogether, so that in the event that you do want to pass actual relative paths, they are correctly interpreted as relative to the current location:

Function Zip {
    Param
    (
        [Parameter(Mandatory)] # make sure a value is passed          
        [string]$zipFile
        ,
        [Parameter(Mandatory)] # make sure a value is passed
        [string[]]$toBeZipped
    )
    # Don't change the location, use & to invoke 7z by its full path.
    $null = & "C:\Program Files\7-Zip\7z.exe" A -tzip $zipFile $toBeZipped
    # You may want to add error handling here.
}

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[1] When Get-ChildItem output stringifies to file names only:

Note:

• If Get-ChildItem output is to be passed to other file-processing cmdlets, say Rename-Item, the problem can be bypassed by providing input to them via the pipeline, which implicitly binds to the target cmdlet’s -LiteralPath parameter by full path – see this answer for more information.

• The related Get-Item cmdlet output always stringifies to the full path, fortunately.

• In PowerShell (Core) v6.1+, Get-ChildItem too always stringifies to the full path, fortunately.

The following therefore only applies to Get-ChildItem in Windows PowerShell:

The problem is twofold:

• Even PowerShell’s built-in cmdlets bind file / directory arguments (parameter values – as opposed to input via the pipeline) not as objects, but as strings (changing this behavior is being discussed in GitHub issue #6057).

• Therefore, for robust argument-passing, you need to ensure that your Get-ChildItem output consistently stringifies to full paths, which Get-ChildItem does not guarantee – and it’s easy to forget when name-only stringification occurs or even that you need to pay attention to it at all.

Always passing the .FullName property values instead is the simplest workaround or, for reliable operation with any PowerShell provider, not just the filesystem, .PSPath.

[System.IO.FileInfo] and [System.IO.DirectoryInfo] instances output by a Get-ChildItem command stringify to their file names only, if and only if:

• If one or more literal directory paths are passed to -LiteralPath or -Path (possibly as the 1st positional argument) or no path at all is passed (target the current location); that is, if the contents of directories are enumerated.

• and does not also use the -Include / -Exclude parameters (whether -Filter is used makes no difference).

• By contrast, whether or not the following are also present makes no difference:

  • -Filter (optionally as the 2nd positional argument, but note that specifying a wildcard expression such as *.txt as the 1st (and possibly only) positional argument binds to the -Path parameter)
  • -Recurse (by itself, but note that it is often combined with -Include / -Exclude)

Example commands:

# NAME-ONLY stringification:

Get-ChildItem | % ToString # no target path

Get-ChildItem . | % ToString # path is literal dir.

Get-ChildItem . *.txt | % ToString  # path is literal dir., combined with -Filter

# FULL PATH stringification:

Get-ChildItem foo* | % ToString # non-literal path (wildcard)

Get-ChildItem -Recurse -Include *.txt | % ToString # use of -Include

Get-ChildItem file.txt | % ToString # *file* path