<s> """<STR_LIT>""" <EOL> from characteristic import attributes <EOL> from pyrsistent import PClass , field , PVector , pvector <EOL> from twisted . python . reflect import namedAny <EOL> @ attributes ( [ "<STR_LIT>" ] ) <EOL> class PluginNotFound ( Exception ) : <EOL> """<STR_LIT>""" <EOL> def __str__ ( self ) : <EOL> return ( <EOL> "<STR_LIT>" <EOL> "<STR_LIT>" . format ( self . plugin_name ) <EOL> ) <EOL> class InvalidPlugin ( Exception ) : <EOL> """<STR_LIT>""" <EOL> @ attributes ( [ "<STR_LIT>" , "<STR_LIT>" ] ) <EOL> class MissingPluginAttribute ( InvalidPlugin ) : <EOL> """<STR_LIT>""" <EOL> def __str__ ( self ) : <EOL> return ( <EOL> "<STR_LIT>" <EOL> "<STR_LIT>" <EOL> "<STR_LIT>" <EOL> . format ( <EOL> plugin_name = self . plugin_name , <EOL> module_attribute = self . module_attribute , <EOL> ) <EOL> ) <EOL> @ attributes ( [ "<STR_LIT>" , "<STR_LIT>" , "<STR_LIT>" , "<STR_LIT>" ] ) <EOL> class InvalidPluginType ( InvalidPlugin ) : <EOL> """<STR_LIT>""" <EOL> def __str__ ( self ) : <EOL> return ( <EOL> "<STR_LIT>" <EOL> "<STR_LIT>" <EOL> "<STR_LIT>" <EOL> "<STR_LIT>" <EOL> . format ( <EOL> plugin_name = self . plugin_name , <EOL> actual_type = self . actual_type , <EOL> plugin_type = self . plugin_type , <EOL> module_attribute = self . module_attribute , <EOL> ) <EOL> ) <EOL> class PluginLoader ( PClass ) : <EOL> """<STR_LIT>""" <EOL> builtin_plugins = field ( PVector , mandatory = True , factory = pvector ) <EOL> module_attribute = field ( str , mandatory = True ) <EOL> plugin_type = field ( type , mandatory = True ) <EOL> def __invariant__ ( self ) : <EOL> for builtin in self . builtin_plugins : <EOL> if not isinstance ( builtin , self . plugin_type ) : <EOL> return ( <EOL> False , <EOL> "<STR_LIT>" <EOL> "<STR_LIT>" . format ( <EOL> plugin_type = self . plugin_type , <EOL> actual_type = type ( builtin ) , <EOL> ) <EOL> ) <EOL> return ( True , "<STR_LIT>" ) <EOL> def list ( self ) : <EOL> """<STR_LIT>""" <EOL> return self . builtin_plugins <EOL> def get ( self , plugin_name ) : <EOL> """<STR_LIT>""" <EOL> for builtin in self . builtin_plugins : <EOL> if builtin . name == plugin_name : <EOL> return builtin <EOL> try : <EOL> plugin_module = namedAny ( plugin_name ) <EOL> except ( AttributeError , ValueError ) : <EOL> raise PluginNotFound ( plugin_name = plugin_name ) <EOL> try : <EOL> plugin = getattr ( plugin_module , self . module_attribute ) <EOL> except AttributeError : <EOL> raise MissingPluginAttribute ( <EOL> plugin_name = plugin_name , <EOL> module_attribute = self . module_attribute , <EOL> ) <EOL> if not isinstance ( plugin , self . plugin_type ) : <EOL> raise InvalidPluginType ( <EOL> plugin_name = plugin_name , <EOL> plugin_type = self . plugin_type , <EOL> actual_type = type ( plugin ) , <EOL> module_attribute = self . module_attribute , <EOL> ) <EOL> return plugin </s>
