Functions/Test-Identity.ps1

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# Licensed under the Apache License, Version 2.0 (the "License");
# you may not use this file except in compliance with the License.
# You may obtain a copy of the License at
#
# http://www.apache.org/licenses/LICENSE-2.0
#
# Unless required by applicable law or agreed to in writing, software
# distributed under the License is distributed on an "AS IS" BASIS,
# WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
# See the License for the specific language governing permissions and
# limitations under the License.

function Test-Identity
{
    <#
    .SYNOPSIS
    Tests that a name is a valid Windows local or domain user/group.
     
    .DESCRIPTION
    Uses the Windows `LookupAccountName` function to find an identity. If it can't be found, returns `$false`. Otherwise, it returns `$true`.
     
    Use the `PassThru` switch to return a `Carbon.Identity` object (instead of `$true` if the identity exists.
 
    .LINK
    Resolve-Identity
 
    .LINK
    Resolve-IdentityName
 
    .EXAMPLE
    Test-Identity -Name 'Administrators
     
    Tests that a user or group called `Administrators` exists on the local computer.
     
    .EXAMPLE
    Test-Identity -Name 'CARBON\Testers'
     
    Tests that a group called `Testers` exists in the `CARBON` domain.
     
    .EXAMPLE
    Test-Identity -Name 'Tester' -PassThru
     
    Tests that a user or group named `Tester` exists and returns a `System.Security.Principal.SecurityIdentifier` object if it does.
    #>

    [CmdletBinding()]
    param(
        [Parameter(Mandatory=$true)]
        [string]
        # The name of the identity to test.
        $Name,
        
        [Switch]
        # Returns a `Carbon.Identity` object if the identity exists.
        $PassThru
    )

    Set-StrictMode -Version 'Latest'

    Use-CallerPreference -Cmdlet $PSCmdlet -Session $ExecutionContext.SessionState
    
    $identity = [Carbon.Identity]::FindByName( $Name )
    if( -not $identity )
    {
        return $false
    }

    if( $PassThru )
    {
        return $identity
    }
    return $true
}