refactor: Use cached_property to cache the show_debug2

[e3243eric]

What was wrong?

Issue #159

How was it fixed?

Replace cached_show_debug2_property with cached_property, and add the cached-property package in install_requires.
cached_property has the untyped issue, so I add the # type: ignore.

To-Do

• Clean up commit history

• Add entry to the release notes

Cute Animal Picture

[fselmo]

First, thanks for tackling this @e3243eric!

At this point this issue is a bit older and I have a few thoughts I wanted to throw around. This strays a bit further from a Good First Issue tag but alas, it may be good to have some conversation around this since I'm sure this will come up again in other repos.

• cached-property doesn't seem like it has been maintained since mid 2020. I'd rather not introduce another dependency to eth-utils that we may have to get rid of in the future. This is a bit weaker argument as it may not need all that much maintenance.

• @cached_property has been a decorator since python 3.8 as part of the functools module. If we can use this for python versions 3.8 and above, that would be quite nice. Python 3.6 has already been marked as not being supported and should probably be dropped from eth-utils as well. Python 3.7 is being marked as not supported only 9 months from now according to the link referenced.

With the above in mind, I think I lean towards only requiring this for python versions below 3.8, otherwise importing the functools decorator.

So... in setup.py:

install_requires=[
        "eth-hash>=0.3.1,<0.6.0",
        "eth-typing>=3.0.0,<4.0.0",
        "toolz>0.8.2,<1;implementation_name=='pypy'",
        "cytoolz>=0.10.1,<1.0.0;implementation_name=='cpython'",
        "cached-property>=1.5.2,<2; python_version < '3.8'",  # this is the relevant change
    ],

Then in logging.py:

import sys
if sys.version_info < (3, 8):
    from cached_property import cached_property
else:
    from functools import cached_property

I believe the above should work. Curious on others' thoughts here.

CC: @kclowes, @pacrob

[e3243eric]

I updated the code like the @fselmo comment, it works, but I got a lint issue.

• When the python version is 3.8+, I import cached-property from functools module. Lint gets the unused error because warn_unused_ignores of mypy is set.
  eth_utils/logging.py:23: error: unused "type: ignore" comment

• When the python version is older than 3.8, the cached-property module needs the "type: ignore" comment to pass the lint check.

I can pass the CI because the python version of CI lint is 3.6.

[fselmo]

I updated the code like the @fselmo comment, it works, but I got a lint issue.

Hmm I think this is OK. We should probably drop 3.6 support and update the lint job to run with the latest supported version but I can handle that in a separate PR. Thanks for making that change and confirming it works well 👍🏼. I'll just wait to see if anyone else has an opinion here before merging. Thanks again.

[kclowes]

Curious on others' thoughts here.

@fselmo - Yep, this is the solution I would do too.

Thanks for all the PRs @e3243eric!