[tahoe-lafs-trac-stream] [Tahoe-LAFS] #2782: code reorg: less inheritance, more delegation/composition

[Tahoe-LAFS]

#2782: code reorg: less inheritance, more delegation/composition
------------------------+-----------------------
     Reporter:  warner  |      Owner:
         Type:  task    |     Status:  new
     Priority:  minor   |  Milestone:  undecided
    Component:  code    |    Version:  1.11.0
   Resolution:          |   Keywords:
Launchpad Bug:          |
------------------------+-----------------------

Comment (by meejah):

 The basic pattern for doing this refactoring would look like:

  - anything remotely complex that's created in an `__init__` method
 becomes and arg
  - the "make complex thing" work moves from `__init__` to some factory-
 method
  - repeat recursively ;)

 So the last thing is the hard part, especially to avoid a "massive
 refactor everything" type of branch/PR. I think the first step would be to
 simply look at dependencies. I don't feel I know enough about `Node` /
 `Client` to know if merging them is appropriate etc. It's fine to leave
 them as a subclasses for now I think -- especially because `Node` only
 really has a couple dependencies in the above model: a tempdir and a tub.
 So, these would have to be passed into `Client` too so that `super()` can
 get called properly.

 It should also be possible to "start slow" and move things out one or two
 dependencies at a time. From a quick grep it doesn't look like `Node()` is
 ever constructed by itself, so we should be able to move its dependencies
 into args-to-Client without making a `create_node` factory-method.

 So a start would be:

 - introduce a `create_client` factory-method, taking `basedir` and `tub`
 - change Node's constructor to get rid of `self.create_tub` and (most of)
 `init_tempdir`
 - move (most of) `Node.create_tub` to a factory method (or even just make
 it @staticmethod?)

 This would probably give a good idea of how this would look/work, and
 would even probably be land-able without anything else changing...From
 there, it would be a "small matter of programming" to do something similar
 for `Client`'s dependencies, and a `create_client()` factory method.

--
Ticket URL: <https://tahoe-lafs.org/trac/tahoe-lafs/ticket/2782#comment:1>
Tahoe-LAFS <https://Tahoe-LAFS.org>
secure decentralized storage