Applying decorators conditionally using type constraints #159
Description
Hi!
We are using Scrutor to apply generic decorators to command handlers and query handlers. This means we have for example a generic ICommandHandler<TCommand> interface and a specific handler implementation which then handles a specific command, e.g. AddPersonCommandHandler : ICommandHandler<AddPerson>.
We apply generic decorators for cross-cutting concerns like transactions, logging, and so on.
Also, we use decorators for permission checks, this looks like this for example:
class AccessValidationCommandHandlerDecorator<TCommand> : ICommandHandler<TCommand>
where TCommand : IAccessRestricted
{
private readonly ICommandHandler<TCommand> decoratee;
public AccessValidationCommandHandlerDecorator(ICommandHandler<TCommand> decoratee)
{
this.decoratee = decoratee;
}
void ICommandHandler<TCommand>.Handle(TCommand command)
{
// Do access validation
this.decoratee.Handle(command);
}
}The decorator in this example uses a generic type constraint for TCommand so that the decorator should only apply to those ICommandHandler<TCommand> implementations where the TCommand implements the IAccessRestricted interface.
We are coming from Simple Injector where this use case is supported and documented here: https://docs.simpleinjector.org/en/latest/aop.html#applying-decorators-conditionally-using-type-constraints
It seems like Scrutor doesn't consider the generic type constraints and tries to apply the decorator to all ICommandHandler<TCommand> implementations regardless of the generic type constraint which leads to an exception on startup because the generic type constraint is not satisfied.
Would it be possible to support that use case and that Scrutor considers the generic type constraints when applying decorators?