functions/Get-DbaDbUser.ps1

function Get-DbaDbUser {
    <#
    .SYNOPSIS
        Gets database users
 
    .DESCRIPTION
        Gets database users
 
    .PARAMETER SqlInstance
        The target SQL Server instance or instances
 
    .PARAMETER SqlCredential
        Allows you to login to SQL Server using alternative credentials
 
    .PARAMETER Database
        To get users from specific database(s)
 
    .PARAMETER ExcludeDatabase
        The database(s) to exclude - this list is auto populated from the server
 
    .PARAMETER ExcludeSystemUser
        This switch removes all system objects from the user collection
 
    .PARAMETER EnableException
        By default, when something goes wrong we try to catch it, interpret it and give you a friendly warning message.
        This avoids overwhelming you with "sea of red" exceptions, but is inconvenient because it basically disables advanced scripting.
        Using this switch turns this "nice by default" feature off and enables you to catch exceptions with your own try/catch.
 
    .NOTES
        Tags: Security, Database
        Author: Klaas Vandenberghe (@PowerDbaKlaas)
 
        Website: https://dbatools.io
        Copyright: (c) 2018 by dbatools, licensed under MIT
        License: MIT https://opensource.org/licenses/MIT
 
    .EXAMPLE
        PS C:\> Get-DbaDbUser -SqlInstance sql2016
 
        Gets all database users
 
    .EXAMPLE
        PS C:\> Get-DbaDbUser -SqlInstance Server1 -Database db1
 
        Gets the users for the db1 database
 
    .EXAMPLE
        PS C:\> Get-DbaDbUser -SqlInstance Server1 -ExcludeDatabase db1
 
        Gets the users for all databases except db1
 
    .EXAMPLE
        PS C:\> Get-DbaDbUser -SqlInstance Server1 -ExcludeSystemUser
 
        Gets the users for all databases that are not system objects, like 'dbo', 'guest' or 'INFORMATION_SCHEMA'
 
    .EXAMPLE
        PS C:\> 'Sql1','Sql2/sqlexpress' | Get-DbaDbUser
 
        Gets the users for the databases on Sql1 and Sql2/sqlexpress
 
    #>

    [CmdletBinding()]
    param (
        [parameter(Mandatory, ValueFromPipeline)]
        [Alias("ServerInstance", "SqlServer")]
        [DbaInstanceParameter[]]$SqlInstance,
        [PSCredential]$SqlCredential,
        [object[]]$Database,
        [object[]]$ExcludeDatabase,
        [switch]$ExcludeSystemUser,
        [Alias('Silent')]
        [switch]$EnableException
    )

    process {
        foreach ($instance in $SqlInstance) {
            try {
                $server = Connect-SqlInstance -SqlInstance $instance -SqlCredential $sqlcredential
            } catch {
                Stop-Function -Message "Failure" -Category ConnectionError -ErrorRecord $_ -Target $instance -Continue
            }

            $databases = $server.Databases | Where-Object IsAccessible

            if ($Database) {
                $databases = $databases | Where-Object Name -In $Database
            }
            if ($ExcludeDatabase) {
                $databases = $databases | Where-Object Name -NotIn $ExcludeDatabase
            }

            foreach ($db in $databases) {

                $users = $db.users

                if (!$users) {
                    Write-Message -Message "No users exist in the $db database on $instance" -Target $db -Level Verbose
                    continue
                }
                if (Test-Bound -ParameterName ExcludeSystemUser) {
                    $users = $users | Where-Object { $_.IsSystemObject -eq $false }
                }

                $users | ForEach-Object {

                    Add-Member -Force -InputObject $_ -MemberType NoteProperty -Name ComputerName -value $server.ComputerName
                    Add-Member -Force -InputObject $_ -MemberType NoteProperty -Name InstanceName -value $server.ServiceName
                    Add-Member -Force -InputObject $_ -MemberType NoteProperty -Name SqlInstance -value $server.DomainInstanceName
                    Add-Member -Force -InputObject $_ -MemberType NoteProperty -Name Database -value $db.Name

                    Select-DefaultView -InputObject $_ -Property ComputerName, InstanceName, SqlInstance, Database, CreateDate, DateLastModified, Name, Login, LoginType, AuthenticationType, State, HasDbAccess, DefaultSchema
                }
            }
        }
    }

    end {
        Test-DbaDeprecation -DeprecatedOn "1.0.0" -EnableException:$false -Alias Get-DbaDatabaseUser
    }
}