Background

Hello there! The Python packaging ecosystem has standardized on the interface for build backends (PEP 517/PEP 660) and the format for metadata declaration (PEP 621/PEP 631).

So, I'm spending my free time updating important projects so that they are modernized and set an example for others 😄

The is a follow-up topydantic/pydantic#4282

Summary of changes

Metadata

This implementsPEP 621 and removes Flit as a development dependency, allowingpip to be used directly which simplifies the contributing workflow and CI/CD. The build backendhatchling (of which I am a maintainer in thePyPA) is now used as that is the default in the officialPython packaging tutorial. Hatchling is available on all the major distribution channels such asDebian,Fedora,Arch Linux,conda-forge,Nixpkgs,Alpine Linux,FreeBSD,Gentoo Linux,MacPorts,OpenEmbedded,Spack, etc.

Python support

The earliest supported Python 3 version of Hatchling is 3.7, therefore I've also set that as the minimum here. Python 3.6 is EOL and other build backends likeflit-core andsetuptools also dropped support. Python 3.6 accounts for 3-4% of downloads in the last month:https://pypistats.org/packages/fastapi

If support is still desired for some reason, I can keep the existing cap and only require 3.7+ in CI/CD.

Documentation

I updated the contributing docs, which accounts for most of the diff. Luckily, they were written in such a way that going fromflit topip didn't alter semantics for any language!

Future

• We now have the ability to ship optional wheels compiled with Mypyc, as Blackrecently did, to be even faster inbenchmarks. Though as@tiangolo mentioned offline, it may be best to wait for the great work@samuelcolvin is doing on Pydantic v2 to be over to be sure we don't cause any disruptions in their test suite.
• We could source the version from Git