functions/filter/Test-PSFFilter.ps1

function Test-PSFFilter {
<#
    .SYNOPSIS
        Tests a filter expression on whether it is valid.
     
    .DESCRIPTION
        Tests a filter expression on whether it is valid.
        Can also validate, that it will work with the specified condition set.
     
    .PARAMETER Expression
        The filter expression to validate.
     
    .PARAMETER ConditionSet
        The condition set object (as returned by Get-PSFFilterConditionSet) to validate against the expression.
     
    .PARAMETER SetModule
        The name of the module from which to pick up the condition set to validate against the expression.
     
    .PARAMETER SetName
        The name of the condition set to validate against the expression.
     
    .EXAMPLE
        PS C:\> Test-PSFFilter -Expression 'OSWindows -or EnvAzurePipelines'
     
        Validates the syntax of the "OSWindows -or EnvAzurePipelines" expression (which is correct).
     
    .EXAMPLE
        PS C:\> Test-PSFFilter -Expression 'OSWindows -or EnvAzurePipelines' -SetModule PSFramework -SetName Environment
     
        Validates the syntax of the "OSWindows -or EnvAzurePipelines" expression (which is correct).
        It then compares it to the latest version of the Environment ConditionSet from within the PSFramework and validates, that it contains the conditions used in the expression ("OSWindows" and "EnvAzurePipelines").
#>

    [OutputType([bool])]
    [CmdletBinding(DefaultParameterSetName = 'default')]
    param (
        [Parameter(Mandatory = $true)]
        [string]
        $Expression,
        
        [Parameter(Mandatory = $true, ParameterSetName = 'Object')]
        [PSFramework.Filter.ConditionSet]
        $ConditionSet,
        
        [Parameter(Mandatory = $true, ParameterSetName = 'Name')]
        [PsfArgumentCompleter('PSFramework.Filter.SetModule')]
        [string]
        $SetModule,
        
        [Parameter(Mandatory = $true, ParameterSetName = 'Name')]
        [string]
        $SetName
    )
    
    process {
        $conditionSetObject = $null
        if ($SetModule -or $ConditionSet) {
            $conditionSetObject = Resolve-PsfFilterConditionSet -ConditionSet $ConditionSet -SetModule $SetModule -SetName $SetName -Cmdlet $PSCmdlet
        }
        
        try { $filter = New-Object PSFramework.Filter.Expression($Expression, $conditionSetObject) }
        catch { return $false }
        
        if (-not $conditionSetObject) { return $true }
        
        $success = $true
        foreach ($condition in $filter.Conditions) {
            if ($conditionSetObject.Conditions.Name -contains $condition) { continue }
            Write-PSFMessage -Level Verbose -String 'Test-PSFFilter.Condition.NotInSet' -StringValues $condition -Target $filter
            $success = $false
        }
        return $success
    }
}