Plugin Extension

As gofer plugins are written and shared throughout the open source community, it seems likely that rather than writing your plugin from scratch, it would be useful to be able to extend one that already exists. Plugins have an API for extending their remote API with remote objects provided by other plugins. Plugin extension can also be specified in the plugin descriptor using the extends property

Extending

What can be imported:

• class object
• function object

Using the descriptor property:

Example:

plugin: dog can extend the animals plugin. Using this method will add all of the dog API to the animals API.

[main]
enabled=1
extends=animals

Using the API:

Example:

plugin: animals

class Dog:
   @remote
   def bark(self):
       pass

plugin: myplugin

from gofer.agent.plugin import Plugin

animals = Plugin.find('animals')
plugin = Plugin.find(__name__)

# just import Dog
plugin += animals['Dog']

# import everything
plugin += animals

Inheritance

Imported class objects may be used as if imported using the standard import directive. When used as a superclass, the inherited methods will be exposed (@remote) as decorated in the superclass.

Examples:

from gofer.agent.plugin import Plugin

# import Dog from animals plugin

animals = Plugin.find('animals')
Dog = animals['Dog']

class Retriever(Dog):
   @remote(secret='wagf')
   def fetch(self):
       pass

Results in the following remote API:

Retriever:

• bark()

  • auth: None

• fetch()

  • auth: shared secret

However, notice that the auth on the inherited bark() is different than fetch(). To change this, simply override the method and re-decorate as needed:

from gofer.agent.plugin import Plugin

# import Dog from animals plugin

animals = Plugin.find('animals')
Dog = animals['Dog']

class Retriever(Dog):

   @remote(secret='wag')
   def bark(self):
       Dog.bark(self)

   @remote(secret='wag')
   def fetch(self):
       pass

Delegation

In many cases, plugins may choose to leverage imported objects by delegation rather than inheritance.

In this example, the Old McDonald toy does not extend Dog but rather delegates the functionality of a dog bark() to an instance of Dog:

from gofer.agent.plugin import Plugin

# import Dog from animals plugin

animals = Plugin.find('animals')
Dog = animals['Dog']

# Old McDonald toy
class Toy:
   @remote
   def theDog(self):
       dog = Dog()
       dog.bark()