CreateLogger<T>() should return ILogger<T> #312
Description
Since ILogger<T> already is an ILogger, shouldn't LoggerFactoryExtensions.CreateLogger<T>() return an ILogger<T> instead of an ILogger?
In order to automatically inject a logger, it needs to be of type ILogger<T>. If one needs to create an instance of a class with such a type in the constructor manually (e.g. in a unit test), ILoggerFactory is required (either way, since we can't construct Logger<T> without one).
However, no method or extension of that class is able to construct the required type ILogger<T> by itself. Instead, the type has to be created manually with new Logger<T>(factory) which is kind of awkward, especially since it internally calls factory.CreateLogger<T>() - that is, I'm now passing a logger factory to a logger I created in order to construct itself ...
The sad thing is that the neither of these perfectly valid looking options work
ILogger<Foo> foo = factory.CreateLogger<Foo>();
ILogger<Foo> bar = (ILogger<Foo>)factory.CreateLogger<Foo>();
where the second one explodes with a firework at runtime.
My suggestion would be to implement CreateLogger<T>() as
public static ILogger<T> CreateLogger<T>(this ILoggerFactory factory)
{
if (factory == null)
{
throw new ArgumentNullException(nameof(factory));
}
return new Logger<T>(factory);
}
and the constructor of Logger<T> as
public Logger(ILoggerFactory factory)
{
_logger = factory.CreateLogger(TypeNameHelper.GetTypeDisplayName(typeof(T), fullName: true));
}
instead.