private static async Task traverse(
this CakeGraph graph, string nodeName,
Func <string, CancellationTokenSource, Task> executeTask,
CancellationTokenSource cancellationTokenSource,
IDictionary <string, Task> visitedNodes)
{
if (visitedNodes.ContainsKey(nodeName))
{
await visitedNodes[nodeName].ConfigureAwait(false);
return;
}
var token = cancellationTokenSource.Token;
var dependentTasks = graph.Edges
.Where(_ => _.End.Equals(nodeName, StringComparison.OrdinalIgnoreCase))
.Select(_ =>
{
var task = graph.traverse(_.Start, executeTask, cancellationTokenSource, visitedNodes);
visitedNodes[_.Start] = task;
return(task);
})
.ToArray();
if (dependentTasks.Any())
{
TaskCompletionSource <object> tcs = new TaskCompletionSource <object>();
token.Register(() => tcs.TrySetCanceled(), false);
await Task.WhenAny(Task.WhenAll(dependentTasks), tcs.Task).ConfigureAwait(false);
}
// The below line does work correctly, but does not bubble up the TaskCanceledException
// await executeTask(nodeName, cancellationTokenSource).ConfigureAwait(false);
await Task.Factory.StartNew(() => executeTask(nodeName, cancellationTokenSource), token).ConfigureAwait(false);
}
public static async Task Traverse(this CakeGraph graph, string target,
Func <string, CancellationTokenSource, Task> executeTask)
{
if (!graph.Exist(target))
{
return;
}
if (graph.hasCircularReferences(target))
{
throw new CakeException("Graph contains circular references.");
}
var cancellationTokenSource = new CancellationTokenSource();
var visitedNodes = new Dictionary <string, Task>();
await graph.traverse(target, executeTask, cancellationTokenSource, visitedNodes);
}