Re: [RFC PATCH] docs: build-platforms: refine requirements on Python build dependencies

[Paolo Bonzini]

On 2/18/23 10:27, Markus Armbruster wrote:
> This one is valid.  Still, it's a "want", not a "must have".  If it was
> a hard "must have", then CentOS 8 support would be in trouble: no mypy
> out of the box, as far as I can tell.

Right, and in fact this is by design: these tools move too fast for a 
version packaged for RHEL8 in 2017 to be useful.

> (A) Commit to keeping mypy happy for all versions of mypy provided by
>      any supported build host
>
> (B) Pick a single mypy version
>
>      Developers have to run this mypy version, or else punt to
>      maintainers.  We'll naturally pick a mypy version the maintainers
>      are happy to run, so no need for them to punt to CI.  We can exploit
>      the full typing power of that mypy version.  We don't have to work
>      around issues older versions may have.
>
>      Developers unable to run this mypy version locally get delayed
>      feedback.  Affects the intersection of "people working on Python
>      code we check with mypy" and "people developing exclusively on older
>      hosts".  If we further intersect with "people doing so on a somewhat
>      regular basis", I posit we get the empty set.
>
> I think (A) is pretty much all downsides.  I like (B), but could be too
> rigid in practice.

I think (B) is feasible.  Right now those developers can use CI and in 
the future we'll have the ability to automatically set up a virtual 
environment for them.

Paolo