Generate *_changed? and *_previously_changed? sigs for belongs_to relations

[cheshire137]

Motivation

Models with a belongs_to relation now have a _changed? and _previously_changed? method since rails/rails#42751. This shipped in Rails 7, see https://github.com/rails/rails/blob/b84fa1083ca7e6422356fdf80cb33751d0a23eff/activerecord/CHANGELOG.md#rails-700alpha1-september-15-2021.

I noticed in my project Sorbet was giving me an error about my model not having a foo_changed? method when I had a belongs_to :foo, even though a respond_to?(:foo_changed?) returned true.

Implementation

I referenced existing _changed? method generation for regular columns on a model:

tapioca/lib/tapioca/dsl/compilers/active_record_columns.rb

Lines 296 to 305 in df5079f

	add_method(
	klass,
	"#{attribute_name}_changed?",
	methods_to_add,
	return_type: "T::Boolean",
	parameters: [
	create_kw_opt_param("from", type: setter_type, default: "T.unsafe(nil)"),
	create_kw_opt_param("to", type: setter_type, default: "T.unsafe(nil)"),
	],
	)

While @erinnachen pointed out https://github.com/Shopify/tapioca/blob/main/lib/tapioca/dsl/compilers/active_record_associations.rb looked to be the compiler for methods coming from belongs_to relations, so I added the new method generation there.

I verified in the Rails implementation in https://github.com/rails/rails/pull/42751/files#diff-084ec489ba3b9f2e388734a99876f0d94776111278acfe4901235dca570040c5 that the new methods take no parameters.

Tests

I updated existing tests to expect the new method signatures to be present.

[cheshire137]

Is there a good way of checking the version of Rails being targeted? We could avoid generating these signatures for pre-Rails 7 if so.

[abraham]

I'm not sure if it's recommended but it looks like you could do this

Suggested change

	if reflection.is_a?(ActiveRecord::Reflection::BelongsToReflection)
	if reflection.is_a?(ActiveRecord::Reflection::BelongsToReflection) && Rails::VERSION::MAJOR >= 7

[cheshire137]

Ooh, thanks! I'll look around the repo, see if there are other such checks like this and, if so, I'll add this one.

[cheshire137]

Hmm, no such uses:

I do see a #rails_version used in tests, so I can investigate that.

[KaanOzkan]

You can use RubyGems API

tapioca/lib/tapioca/dsl/compilers/active_job.rb

Line 81 in b3cec5b

if ::Gem::Requirement.new(">= 7.0").satisfied_by?(::ActiveJob.gem_version)

And in tests you can use the template and rails_version helpers

tapioca/spec/tapioca/dsl/compilers/active_job_spec.rb

Line 76 in b3cec5b

<% if rails_version(">= 7.0") %>

[cheshire137]

That worked great, thank you!

[cheshire137]

I have signed the CLA!

[paracycle]

Thanks for the changes, this looks great!

[NexusGamingHub]

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