port to packaging to avoid pkg_resources import cost

[RonnyPfannschmidt]

its expensive to import pkg_resources if all that's needed is version parsing of packaging

it should be relatively straightforward to simplify and port

[asottile]

It's not just that, is there a direct replacement for

pre-commit/pre_commit/constants.py

Line 21 in c0b1f2f

VERSION = pkg_resources.get_distribution('pre-commit').version

[RonnyPfannschmidt]

@asottile that part needs a little expansion, personally i'd propose setuptools_scm and writing a version file to the package as importation is so much faster than workingset construction and packageset iteration

[asottile]

Nothing personal, but I'm not going to use setuptools-scm, it seems a bit over engineered for what equates to writing a text file.

There's three parts here that need solving:

• self-referential version number
• resource files
• version comparison

The first can reasonably be solved with writing a version number at install time, I really don't want to get setup_requires (eggs) involved.

The second is a bit trickier, maybe importlib_resources? (backport of 3.7 package) -- that pulls in a lot of dependencies for something that to me seems like it should be simple. Should I care to support eggs and zipimport as distribution methods for pre-commit? Should I require consumers to use pip (or equivalent)?

The third is by far the easiest, pre-commit doesn't have any complicated version numbers (yet, and I don't plan on it) and really it can be replaced with map(int, s.split('.'))

[asottile]

and hmm, even setuptools-scm suggests using pkg_resources: https://github.com/pypa/setuptools_scm#setuppy-usage

[RonnyPfannschmidt]

@asottile im the maintainer there that wrote the suggestion, its generally more useful for packages that do not have import time constraints - for example pytest uses the entrypoint system excessively anyway