Explicitly define :_default_attribute_values using class_attribute in child class

[k-tsuchiya-jp]

Detail

Fix #100

Checklist

Before submitting the PR make sure the following are checked:

• This Pull Request is related to one change. Unrelated changes should be opened in separate PRs.
• Commit message has a detailed description of what changed and why. If this PR fixes a related issue include it in the commit message. Ex: [Fix #issue-number]
• Tests are added or updated if you fix a bug or add a feature.
• CHANGELOG files are updated for the changed libraries if there is a behavior change or additional feature. Minor bug fixes and documentation changes should not be included.

[k-tsuchiya-jp]

before

$ BUNDLE_GEMFILE=/home/zenet/default_value_for/gemfiles/rails_80.gemfile bundle exec rake
/home/k-tsuchiya-jp/.rbenv/versions/3.3.6/bin/ruby test.rb

Testing with ruby version 3.3.6

Testing with Active Record version 8.0.1

Testing with Action Pack version 8.0.1

Run options: --seed 21384

# Running:

...................................F..

Finished in 0.207456s, 183.1710 runs/s, 265.1159 assertions/s.

  1) Failure:
DefaultValuePluginTest#test_multiple_default_values_in_subclass_with_default_values_in_parent_class [test.rb:236]:
Expected: 5678
  Actual: nil

38 runs, 55 assertions, 1 failures, 0 errors, 0 skips
rake aborted!

after

$ BUNDLE_GEMFILE=/home/zenet/default_value_for/gemfiles/rails_80.gemfile bundle exec rake
/home/k-tsuchiya-jp/.rbenv/versions/3.3.6/bin/ruby test.rb

Testing with ruby version 3.3.6

Testing with Active Record version 8.0.1

Testing with Action Pack version 8.0.1

Run options: --seed 45765

# Running:

......................................

Finished in 0.200715s, 189.3235 runs/s, 279.0031 assertions/s.

38 runs, 56 assertions, 0 failures, 0 errors, 0 skips

[jrafanie]

I'll need to dig into the history of the original code to better understand why we avoided initializing/resetting these class attributes previously and why it's ok now. I see the tests are green on older rails versions but I'm not sure the reason why this code was written like this.

@k-tsuchiya-jp did you figure out why your change is safe to do for rails 6 through 8?

[jrafanie]

Thanks for the possible fix for #100. See comment above. If you can explain it to me, I'd be more confident this change wouldn't break older versions of rails. Thank you!

[jrafanie]

@k-tsuchiya-jp thanks, I missed this comment (#100 (comment)) before... after reviewing it and testing it locally with ruby 3.2 and 3.3 on the supported rails, your change is great. The original code dates back to 2012.

Thanks for your contribution.

[jrafanie]

@k-tsuchiya-jp released 4.1.1... thanks again!