Re: [BuildStream] Proposal: Consider adding type hints

[Benjamin Schubert <contact benschubert me>]

> On Tue, 2019-06-25 at 21:39 +0100, Chandan Singh wrote:
>
> Hi all,
> I wanted to start the conversation about adding type hints (as specified by PEP
> 484 [1]) to some parts of the BuildStream code.

My +1 definitely!


‐‐‐‐‐‐‐ Original Message ‐‐‐‐‐‐‐
On Wednesday, 26 June 2019 10:48, Tristan Van Berkom via buildstream-list <buildstream-list gnome org> wrote:

> > For the public API, we already attempt to add types. However, it is
> > not covered by
> > any automated type analyzer given how it is done as part of the docstring.
> > Switching to type hints would allow one to run static type checkers like
> > mypy [2], pytype [3] pyright [4] etc. Neither of them is quite perfect just yet
> > but they are getting better with time.
>
> I suppose these checkers can only have some measure of success in
> catching errors, and only when the calling code exists in the codebase
> being checked.
>
> I'm curious if we can take this one step further:
>
> -   Can we automatically introduce runtime assertions on function
>     arguments throughout the codebase ?

The answer is yes! https://github.com/Stewori/pytypes does this quite well and can be enabled/disabled at 
import time!

That would mean slightly slower imports but we would be able to typecheck only at test time/on demand.

> -   Can we distinguish between public API surface and internal functions,
>     such that we can perhaps keep the runtime assertions active only
>     on the public API surface, when asserts are disabled with `-O` ?
>
>     Obviously, having runtime assertions at every function entry point
>     would be expensive, but worthwhile in development, but surely a thin
>     layer of type checking on public API entry points is worth the small
>     expense (also worth benchmarking).
>
>     Cheers,
>     -Tristan
Having the pytypes checks at runtime would be usable/disableable if we want. I'm happy to help for getting 
this up and running

Cheers,
Ben