Generating a Graphviz dot file from `WorkflowDefinition`

[tatupesonen]

Hi!

I've built some functionality outside of the library that allows you to generate a Graphviz dot file directly from the WorkflowDefinition. Is this something you'd be interested in upstreaming to your package?

Currently I've manually made the $id, $dependents and $instance fields of Node of the library public because it's needed for my custom extension to work, but if it's integrated into the library the API would largely stay the same.

Here's the source code I currently use for it:

    public function handle()
    {
        $workflow = new ExampleWorkflow();
        $graph = $workflow->definition()->graph();
        echo 'digraph G {' . PHP_EOL;
        echo '    rankdir="LR";' . PHP_EOL;
        echo '    graph [pad="0.5", nodesep="1", ranksep="2"]' . PHP_EOL;
        array_walk($graph->graph, function ($n) use (&$buf) {
            $this->getDot($n, $buf);
        });
    }

    public function getDot(Node $node, &$dot, &$visited = [])
    {
        $visited[$node->id] = true;
        if ($node->dependents) {
            foreach ($node->dependents as $dep) {
                echo '    "' . $node->id . '" -> { "' . $dep->id . '" }' . PHP_EOL;
                if (!$visited[$node->id]) {
                    $this->getDot($dep, $dot, $visited);
                }
            }
        }
    }