Implement ActiveModel::Validations::Confirm compiler

[Tonkpils]

Motivation

Given a class implementing a confirmation validation from ActiveModel::Validations

class User < ApplicationRecord
  validates :password, confirmation: true
end

will generate virtual attributes password_confirmation and password_confirmation=. Without this compiler, usage of those methods will cause an error with Sorbet unless they are shimmed out.

Implementation

The compiler is pretty straightforward iterating over all validators of a gathered constant, selecting only those that implement ConfirmationValidator and generating the necessary methods for each of the attributes in the rbi file. It also skips ActiveRecord::Base since that class includes ActiveModel::Validations but does not implement any of its validations.

Tests

Tests were added

[vinistock]

Would it be possible to figure out the right types based on the columns?

[Tonkpils]

If the it's a subclass of ActiveRecord::Base, we can probably use one of ActiveRecord's API to figure out the column type and translate it to a proper return type. The same could be said for classes that implement ActiveModel::Attributes.

However, since this validations can be added to POROs, we'd have to add logic to differentiate the two. Are we ok with doing that here?

[vinistock]

Good point. Do these validations require you to use Active Model attributes or something that would allow us to fetch the type?

If not, I think it's fine to use T.untyped. Just trying to think if there's a way to get better typing support.

[Tonkpils]

Do these validations require you to use Active Model attributes or something that would allow us to fetch the type?

Unfortunately no, they only require `ActiveModel::Validations

class Foo
   attr_reader :foo

   def initialize(foo)
     @foo = foo
   end

   include ActiveModel::Validations

   validates_confirmation_of :foo
end

f = Foo.new("foo")
f.foo_confirmation = "bar"
f.valid?
=> false
f.errors
=> #<ActiveModel::Errors [#<ActiveModel::Error attribute=foo_confirmation, type=confirmation, options={:attribute=>"Foo"}>]>

[vinistock]

I see. Yeah, it seems like this can be used in pretty much any context, let's go with T.untyped. Thanks for investigating!

[vinistock]

I see. Yeah, it seems like this can be used in pretty much any context, let's go with T.untyped. Thanks for investigating!

[vinistock]

It appears you need to run bin/docs to update the docs.

[Tonkpils]

It appears you need to run bin/docs to update the docs.

All fixed 🙇

[vinistock]

I think you might need to rebase the branch because of #1643. There are some typechecking and test errors.

[Tonkpils]

All done @vinistock 🙇

[vinistock]

It seems that typechecking is still failing.

[Tonkpils]

@vinistock looks like this will be fixed by #1648?

[vinistock]

Okay, rebasing now should fix the CI.

[Tonkpils]

Done!

[vinistock]

Thank you for the contribution!