In order to act on an error thrown from an individual task, you can use the OnError task extension. This will give you the opportunity to act on the error. If you want the error to propagate as normal, you can rethrow the exception.

Task("A")
    .Does(() =>
{
})
.OnError(exception =>
{
    // Handle the error here.
});

Ignoring errors

To automatically swallow errors that occur in a task, you can use the ContinueOnError task extension. The ContinueOnError extension cannot be combined with OnError.

Task("A")
    .ContinueOnError()
    .Does(() =>
{

});

Reporting errors

If you want to report an error without affecting its propagation or resulting stack trace, you can use the ReportError task extension. Any exceptions thrown in the scope of ReportError will be swallowed.

Task("A")
    .Does(() =>
{
})
.ReportError(exception =>
{
    // Report the error.
});

Aborting the build

If something has gone wrong that you cannot recover from, you should throw an exception to indicate it. The Cake script runner will then log the error (using the Error method) and return exit code 1 to indicate that something went wrong.

Task("Check-ReleaseNotes")
    .Does(() =>
{
    var releaseNotes = ParseReleaseNotes("./ReleaseNotes.md");
    if(releaseNotes.Version.ToString() != nugetVersion)
    {
        throw new Exception(String.Format("Release notes are missing an entry for v{0}. Latest release notes are for v{1}", nugetVersion, releaseNotes.Version));
    }
});

Deferring on error

DeferOnError allows a given task the ability to defer all exceptions until the end of the task execution. This way tasks can run all actions to completion before failing. This can have some value when you work with something like multiple unit test projects, or multiple publishes. You can see the output of the entire task, and not just where it failed.

Task("A")
    .Does(() =>
{
    throw new Exception();
})
.DoesForEach(GetFiles("**/*.txt"), (file) =>
{
   // Take action on the file.
})
.DeferOnError();