Make belongs_to relation non-nilable by default

[wpride]

Since Rails 5 the belongs_to relation has been required by default. To make this non-required you must add optional: true to the relation.

This change updates the association methods to reflect this.

Curious what you all think about this change; if it looks good I will add tests.

[codecov-io]

Codecov Report

Merging #144 into master will increase coverage by <.01%.
The diff coverage is 100%.

@@            Coverage Diff             @@
##           master     #144      +/-   ##
==========================================
+ Coverage   98.36%   98.36%   +<.01%     
==========================================
  Files         169      169              
  Lines        1830     1832       +2     
==========================================
+ Hits         1800     1802       +2     
  Misses         30       30

Impacted Files	Coverage Δ
.../sorbet-rails/model_plugins/active_record_assoc.rb	100% <100%> (ø)	⬆️

---

Continue to review full report at Codecov.

Legend - Click here to learn more
Δ = absolute <relative> (impact), ø = not affected, ? = missing data
Powered by Codecov. Last update ec48634...00d024a. Read the comment docs.

[hdoan741]

Sounds good. I verified that this is indeed the behavior in Rails 5.
I'm curious though: what happen if you have a belongs_to, but the column is null? Is it just an ActiveRecord level check?

https://blog.bigbinary.com/2016/02/15/rails-5-makes-belong-to-association-required-by-default.html

[wpride]

@manhhung741 Yes, looks like you get an ActiveRecord::NotNullViolation:

Updated expected results

[hdoan741]

Thanks!