Feature #11955

Updated by nobu (Nobuyoshi Nakada) almost 6 years ago

I need to be able to perform logic based on the destination of a current logger, this is currently not possible without `instance_variable_get`. Why would you need to see what destination a logger is going to? There is a common pattern in long lived programs like webservers. You want logs on disk for later reference, but you also want them in STDOUT to make development and debugging easier. Rails does this in development mode. Since there is no way to see if a logger is already going to STDOUT, it gets extended to log to STDOUT so logs show up twice. 

 While that example was complicated the logic I want is very simple: if you have a logger that is logging to STDOUT, do nothing, otherwise log to STDOUT and current logger. You cannot do this today without exposing the destination of the logger. This patch exposes the logger destination and allows us to write code like this: 

 ```ruby ``` 
 def make_sure_logging_to_stdout(logger) 
   unless logger.destination == STDOUT     # <==== Cannot do this today 
     stdout_logger = 
     logger.extend(Module do 
       def add((*args, &block) 
         stdout_logger.add(*args, &block) 
         super(*args, &block) 

 logger = 

 logger.fatal("An error has occured") 

 We should be able to inspect the destination of a logger, this patch enables this functionality.