functions/SPClientUser/Resolve-SPClientUser.ps1

#Requires -Version 3.0

# Resolve-SPClientUser.ps1
#
# Copyright (c) 2017 karamem0
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function Resolve-SPClientUser {

<#
.SYNOPSIS
  Checks whether the specified login name belongs to a valid user.
.PARAMETER ClientContext
  Indicates the client context.
  If not specified, uses the default context.
.PARAMETER ParentObject
  Indicates the web which the user is contained.
.PARAMETER Name
  Indicates login name or e-mail address.
#>


    [CmdletBinding()]
    param (
        [Parameter(Mandatory = $false)]
        [Microsoft.SharePoint.Client.ClientContext]
        $ClientContext = $SPClient.ClientContext,
        [Parameter(Mandatory = $true)]
        [Microsoft.SharePoint.Client.Web]
        $ParentObject,
        [Parameter(Mandatory = $true)]
        [string]
        $Name
    )

    process {
        if ($ClientContext -eq $null) {
            throw "Cannot bind argument to parameter 'ClientContext' because it is null."
        }
        $ClientObject = $ParentObject.EnsureUser($Name)
        Invoke-SPClientLoadQuery `
            -ClientContext $ClientContext `
            -ClientObject $ClientObject `
            -Retrievals $Retrievals
        Write-Output $ClientObject
    }

}