Support platformdirs as drop-in replacement for appdirs

[robjarawan]

Summary

• Feature detection now supports Alternate_modules — if the primary module isn't found, alternates are tried before disabling the feature. The appdirs feature lists platformdirs as an alternate.
• At import time, platformdirs is preferred over appdirs since appdirs is unmaintained and unavailable on RHEL9. Both provide the same API for the three functions we use (site_config_dir, user_config_dir, user_cache_dir).
• Packaging changes (debian/control, RPM spec, pyproject.toml) are left out of this PR since those depend on target platform decisions — figured I'd leave that to whoever knows the packaging side best:D.

Closes #1493

Test plan

• Verify sr3 features shows appdirs as present when only platformdirs is installed
• Verify sr3 features shows appdirs as present when only appdirs is installed
• Verify fallback to hardcoded Linux paths when neither is installed
• Verify config/cache directories resolve correctly on each platform

[github-actions]

Test Results

321 tests   320 ✅  1m 43s ⏱️
  1 suites    1 💤
  1 files      0 ❌

Results for commit 2360ca4.

♻️ This comment has been updated with latest results.

[reidsunderland]

The alternate features thing is interesting, I like how it's an easy automatic substitution.

But thinking ahead towards the eventual removal of appdirs, I'm not sure that the extra code is necessary, and it might cause confusion for users. With the proposed change, when platformdirs is installed, sr3 features will show that appdirs is installed, which is misleading.

Adding platformdirs as a whole separate feature and importing like this might be a little simpler:

if features['platformdirs']['present']:
    import platformdirs as appdirs
elif features['appdirs']['present']:
    import appdirs

It's just a design/opinion thing. @andreleblanc11 or @petersilva do you have any preference?

Hopefully I don't get hit with the wrath of AI for this :D

[robjarawan]

So I reworked this to use your approach - platformdirs is its own feature entry now instead of the Alternate_modules thing. That way sr3 features actually shows which package you have installed instead of being misleading. platformdirs gets preferred when both are present. Pushed in the latest commit.

[reidsunderland]

I don't see any new code on this branch, did you use a different branch or maybe forgot to push the change?

[robjarawan]

Woops, I had it stashed locally and forgot to push — just pushed the fix. platformdirs and appdirs are now separate feature entries instead of using the Alternate_modules fallback. Should be good now!

[robjarawan]

Pushed a refresh for this branch.

This is now rebased onto current development, so the merge conflict should be gone.

@reidsunderland the code that was missing before is definitely in this branch now:

• platformdirs is its own feature entry in sarracenia/featuredetection.py
• appdirs and platformdirs are reported independently by feature detection
• sarracenia/__init__.py prefers platformdirs when present, falls back to appdirs, then falls back to the hardcoded Linux paths
• the old Alternate_modules fallback is not used

I also added focused tests so this is explicit:

• test_platformdirs_is_a_separate_feature
• test_platformdirs_preferred_over_appdirs
• test_appdirs_used_when_platformdirs_missing

Tests:

• python3 -m pytest tests/sarracenia/featuredetection_test.py tests/sarracenia/platformdirs_import_test.py -v - 3 passed
• pycodestyle --max-line-length=119 tests/sarracenia/featuredetection_test.py tests/sarracenia/platformdirs_import_test.py - passed
• git diff --check - passed

[reidsunderland]

This looks good, thanks for the updates.

I should have noted this before, but the packaging stuff should also be updated to prefer platformdirs where available.

• https://github.com/MetPX/sarracenia/blob/development/debian/control (the Depends: section automatically gets filled in by the Python packaging stuff)
• https://github.com/MetPX/sarracenia/blob/development/metpx-sr3.spec#L17

• sarracenia/setup.py

  Lines 106 to 109 in b4fa32f

  	install_requires=[
  	"appdirs", "humanfriendly", "humanize", "jsonpickle", "psutil>=5.3.0",
  	"paramiko", "watchdog",
  	],

• sarracenia/Dockerfile_base

  Line 11 in 25e9335

  RUN apt-get update ; apt-get install -y python3-amqp python3-appdirs python3-dateparser python3-humanfriendly python3-humanize python3-jsonpickle python3-netifaces python3-paho-mqtt python3-paramiko python3-pip python3-psutil python3-watchdog

• sarracenia/requirements.txt

  Line 4 in 25e9335

  jsonpickle

• sarracenia/pyproject.toml

  Line 37 in 25e9335

  "appdirs", "humanfriendly", "humanize", "jsonpickle", "paramiko",

• sarracenia/travis/flow_autoconfig_redhat.sh

  Line 37 in 25e9335

  for PKG in amqp appdirs dateparser watchdog netifaces humanize jsonpickle paho-mqtt psutil xattr rangehttpserver; do

There's a lot of places to adjust and I'm not completely sure how to set up alternatives for each. In Debian we can use:

python3-platformdirs | python3-appdirs

But I'm not sure about the others. If you want we could merge this PR and deal with that separately?