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.Run(() => 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);
}
private static bool HasCircularReferences(this CakeGraph graph, string nodeName, Stack <string> visited = null)
{
visited = visited ?? new Stack <string>();
if (visited.Contains(nodeName))
{
return(true);
}
visited.Push(nodeName);
var hasCircularReference = graph.Edges
.Where(_ => _.End.Equals(nodeName, StringComparison.OrdinalIgnoreCase))
.Any(_ => graph.HasCircularReferences(_.Start, visited));
visited.Pop();
return(hasCircularReference);
}
public static CakeGraph Build(List <CakeTask> tasks)
{
var graph = new CakeGraph();
foreach (var task in tasks)
{
graph.Add(task.Name);
}
foreach (var task in tasks)
{
foreach (var dependency in task.Dependencies)
{
if (!graph.Exist(dependency.Name))
{
const string format = "Task '{0}' is dependent on task '{1}' which does not exist.";
var message = string.Format(CultureInfo.InvariantCulture, format, task.Name, dependency);
throw new CakeException(message);
}
graph.Connect(dependency.Name, task.Name);
}
foreach (var dependee in task.Dependees)
{
if (!graph.Exist(dependee.Name))
{
if (dependee.Required)
{
const string format = "Task '{0}' has specified that it's a dependency for task '{1}' which does not exist.";
var message = string.Format(CultureInfo.InvariantCulture, format, task.Name, dependee.Name);
throw new CakeException(message);
}
}
else
{
graph.Connect(task.Name, dependee.Name);
}
}
}
return(graph);
}