private CompositionResult TryPreviewImportsStateMachine(PartManager partManager,
ComposablePart part, AtomicComposition atomicComposition)
{
var result = CompositionResult.SucceededResult;
if (partManager.State == ImportState.ImportsPreviewing)
{
// We shouldn't nomally ever hit this case but if we do
// then we should just error with a cycle error.
return(new CompositionResult(ErrorBuilder.CreatePartCycle(part)));
}
// Transition from NoImportsStatisified to ImportsPreviewed
if (partManager.State == ImportState.NoImportsSatisfied)
{
partManager.State = ImportState.ImportsPreviewing;
var requiredImports = part.ImportDefinitions.Where(IsRequiredImportForPreview);
// If this atomicComposition gets rolledback for any reason we need to reset our state
atomicComposition.AddRevertActionAllowNull(() => partManager.State = ImportState.NoImportsSatisfied);
result = result.MergeResult(
this.TrySatisfyImportSubset(partManager, requiredImports, atomicComposition));
if (!result.Succeeded)
{
partManager.State = ImportState.NoImportsSatisfied;
return(result);
}
partManager.State = ImportState.ImportsPreviewed;
}
return(result);
}
