Invoke-Step with dependencies

PoshStep.psm1

class DependsOn : System.Attribute {
    [string[]]$Name

    DependsOn([string[]]$name) {
        $this.Name = $name
    }

}

function Invoke-Step {
    <#
        .Synopsis
            Runs a command, taking care to run it's dependencies first
        .Description
            Invoke-Step supports the [DependsOn("...")] attribute to allow you to write tasks or build steps that take dependencies on other tasks completing first.

            When you invoke a step, dependencies are run first, recursively. The algorithm for this is depth-first and *very* naive. Don't build cycles!
       .Example
            function init {
                param()
                Write-Information "INITIALIZING build variables"
            }

            function update {
                [DependsOn("init")]param()
                Write-Information "UPDATING dependencies"
            }

            function build {
                [DependsOn(("update","init"))]param()
                Write-Information "BUILDING: $ModuleName from $Path"
            }

            Invoke-Step build -InformationAction continue

            Defines three steps with dependencies, and invokes the "build" step.
            Results in this output:

            Invoking Step: init
            Invoking Step: update
            Invoking Step: build

    #>
    [CmdletBinding()]
    param(
        [string]$Step,
        [string]$Script
    )
    begin {
        # Source Build Scripts, if any
        if($Script) { . $Script }

        # Don't reset on nested calls
        if(((Get-PSCallStack).Command -eq "Invoke-Step").Count -eq 1) {
            $script:InvokedSteps = @()
            $script:DependencySteps = @()
        }
    }
    end {

        $StepCommand = Get-Command $Step

        $Dependencies = $StepCommand.ScriptBlock.Attributes.Where{ $_.TypeId.Name -eq "DependsOn" }.Name

        foreach($dependency in $Dependencies) {
            if($script:InvokedSteps -notcontains $dependency) {
                Invoke-Step -Step $dependency
            }
        }

        Write-Information -MessageData "Invoking Step: $Step"
        & $StepCommand
        $script:InvokedSteps += $Step
    }
}