[Import-SIG] ImportState vs. ImportSystem

[Nick Coghlan]

On 15 September 2016 at 10:34, Eric Snow <ericsnowcurrently at gmail.com> wrote:
> The question I'd like to focus on is: would it be better to have
> separate ImportState and ImportSystem types, or have a single type
> that fills both roles?  I'm leaning toward keeping them distinct since
> the import machinery *uses* the state and state stands well on its
> own.  Having a distinct ImportState type makes the functionality more
> discoverable and more obvious.  Also, having distinct types helps
> communicate the different layers at play, which invites discovery of
> how the import system operates.

I think distinct is a good way to go, as that lets you tackle the
problem in multiple refactoring and design steps:

1. Encapsulate the existing import state as a private shim that
accesses the `sys` module and use that shim in the existing import
machinery
2. Based on your experience in (1), design a mechanism to more easily
swap out the entire import system with a different one

The reason I suggest that is because PEP 406 mainly foundered on the
problem of maintaining compatibility with existing import system
plugins, and pursuing step 1 should give you a better handle on the
exact scope of that challenge and possible resolutions to it (e.g. a
decimal or asyncio style thread-local context).

Cheers,
Nick.

-- 
Nick Coghlan   |   ncoghlan at gmail.com   |   Brisbane, Australia