decorator.py

def expose_as(cmd_name="", *alternatives):
    """Decorator for exposing functions as subssh commands"""
    
    def expose_function(f):
        def check_args_wrapper(*function_args):
            """
            Check that input f gets called with right amount of 
            arguments. Makes it raise InvalidArguments instead of TypeError when 
            it is supplied invalid amount of arguments.
            
            This is used to distinguish user error from internal app error.  
            """
            if len(function_args) != f.func_code.co_argcount:
                if len(function_args) < f.func_code.co_argcount:
                    raise InvalidArguments("Too few arguments")
                
                # If last arguments does not start with *args
                if f.func_code.co_nlocals - f.func_code.co_argcount != 1: 
                    raise InvalidArguments("Too many arguments")
            # Correct arguments. Execute the original function.
            # This should not ever raise TypeError.
            return f(*function_args)

        # Make check_args_wrapper to look like the original function.
        check_args_wrapper.__name__ = f.__name__
        check_args_wrapper.__doc__ = f.__doc__
        check_args_wrapper.__dict__ = f.__dict__
        

        if not cmd_name:
            # Use name of the function if no name is supplied
            name = f.__name__.replace("_", "-")
        else:
            name = cmd_name
        
        # When f is run from apploader, wrap it with arguments
        # checker function which 
        active.cmds[name] = check_args_wrapper
        for alt_name in alternatives:
            active.cmds[alt_name] = check_args_wrapper
        
        # Calling code gets the real function.
        return f
        
    return expose_function