Benjamin Risher <brisher...@gmail.com> writes:
> Ok, here's my issue. I have a plugin framework I wrote that relies on a
> third party library that I can't change. As a part of that framework, I
> wrote a small stub library to proxy calls to the third party library, so that
> if their api ever changes, plugins written against the stub won't have to
> change, I'll just have to update the back-half that interfaces with the
> library. I think this is called an adapter design pattern...?
>
> plugin --> my api --> their api --> their library
>
> It works, for the most part. Most of my classes look similar to this
>
> class MYClass:
> def __init__(self, *args, **kwargs):
> self.__theirclass = TheirClass(*args, **kwargs)
>
> def __getattr__(self, attr):
> return getattr(self.__theirclass, attr)
>
> What I'm having issue with, is their exception class.
>
> 1. A plugin calls a stub in my library
> 2. That stub calls the corresponding call in the third party library
> 3. The call raises an exception from the library
> 4. The plugin can't catch the exception without importing directly from the
> third party library
>
> What is the correct way to allow plugins to import my stub exception, but
> catch the ones raised by the library?
I would approach this as follows:
* define an exception hiearchy for your wrapper with a common root class
and document those hiearchy to be used for the plugins
* in your wrapper, catch all exceptions
- if it is one of your execptions, you know what to do
- if it is a general Python exception, it likely indicates
a programming error in the plugin or library -- handle
as appropriately (personally, I would "reraise")
- if it is something else, it likely indicates that
the plugin violated its contract (towards your wrapper API) --
handle as appropriate (again, I would "reraise").
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