Public/Drive/Get-GSDrivePermission.ps1

function Get-GSDrivePermission {
    <#
    .SYNOPSIS
    Gets permission information for a Drive file
    
    .DESCRIPTION
    Gets permission information for a Drive file
    
    .PARAMETER User
    The email or unique Id of the user whose Drive file permission you are trying to get

    Defaults to the AdminEmail user
    
    .PARAMETER FileId
    The unique Id of the Drive file
    
    .PARAMETER PermissionId
    The unique Id of the permission you are trying to get. If excluded, the list of permissions for the Drive file will be returned instead
    
    .PARAMETER PageSize
    The page size of the result set
    
    .EXAMPLE
    Get-GSDrivePermission -FileId '1rhsAYTOB_vrpvfwImPmWy0TcVa2sgmQa_9u976'

    Gets the list of permissions for the file Id
    #>

    [cmdletbinding(DefaultParameterSetName = "List")]
    Param
    (
        [parameter(Mandatory = $false,Position = 0,ValueFromPipelineByPropertyName = $true)]
        [Alias('Owner','PrimaryEmail','UserKey','Mail')]
        [string]
        $User = $Script:PSGSuite.AdminEmail, 
        [parameter(Mandatory = $true)]
        [String]
        $FileId, 
        [parameter(Mandatory = $false,ParameterSetName = "Get")]
        [String[]]
        $PermissionId,
        [parameter(Mandatory = $false,ParameterSetName = "List")]
        [Alias('MaxResults')]
        [ValidateRange(1,100)]
        [Int]
        $PageSize = "100"
    )
    Begin {
        if ($User -ceq 'me') {
            $User = $Script:PSGSuite.AdminEmail
        }
        elseif ($User -notlike "*@*.*") {
            $User = "$($User)@$($Script:PSGSuite.Domain)"
        }
        $serviceParams = @{
            Scope       = 'https://www.googleapis.com/auth/drive'
            ServiceType = 'Google.Apis.Drive.v3.DriveService'
            User        = $User
        }
        $service = New-GoogleService @serviceParams
    }
    Process {
        try {
            if ($PermissionId) {
                foreach ($per in $PermissionId) {
                    $request = $service.Permissions.Get($FileId,$per)
                    Write-Verbose "Getting Permission Id '$per' on File '$FileId' for user '$User'"
                    $request.Execute() | Add-Member -MemberType NoteProperty -Name 'User' -Value $User -PassThru | Add-Member -MemberType NoteProperty -Name 'FileId' -Value $FileId -PassThru
                }
            }
            else {
                $request = $service.Permissions.List($FileId)
                $request.SupportsTeamDrives = $true
                $request.PageSize = $PageSize
                Write-Verbose "Getting Permission list on File '$FileId' for user '$User'"
                [int]$i = 1
                do {
                    $result = $request.Execute()
                    $result.Permissions | Add-Member -MemberType NoteProperty -Name 'User' -Value $User -PassThru | Add-Member -MemberType NoteProperty -Name 'FileId' -Value $FileId -PassThru
                    if ($result.NextPageToken) {
                        $request.PageToken = $result.NextPageToken
                    }
                    [int]$retrieved = ($i + $result.Permissions.Count) - 1
                    Write-Verbose "Retrieved $retrieved Permissions..."
                    [int]$i = $i + $result.Permissions.Count
                }
                until (!$result.NextPageToken)
            }
        }
        catch {
            if ($ErrorActionPreference -eq 'Stop') {
                $PSCmdlet.ThrowTerminatingError($_)
            }
            else {
                Write-Error $_
            }
        }
    }
}