Wrong sig for `group().count`

[ghiculescu]

https://api.rubyonrails.org/classes/ActiveRecord/Calculations.html#method-i-count

Person.count returns an Integer

Article.group(:status, :category).count returns a hash of type T::Hash[String, Integer]

Currently there's no sigs for count on an AR::Relation generated, it's left to other places (sorbet rbi generation / sorbet-typed) to define.

However, rbis generated for relations do include Enumerable, which means that by default count is assumed to return Integer. See sorbet.run.

My proposal

I'm not sure if this is a good idea yet, I'd like feedback.

Currently rbis we generate for models include this:

  sig { params(args: T.untyped).returns(Article::ActiveRecord_Relation) }
  def self.group(*args); end

We could change it to this:

  sig { params(args: T.untyped).returns(Article::ActiveRecord_Relation__GROUPED) }
  def self.group(*args); end

And also define this in the same rbi:

class Article::ActiveRecord_Relation__GROUPED < Article::ActiveRecord_Relation
  extend T::Sig
  extend T::Generic
  Elem = type_member(fixed: Article)

  sig { returns(T::Hash[T.any(String, T::Array[String]), Integer]) }
  def count; end
end

I've tested this code statically and it works great. I imagine it might create some runtime problems which is why I want feedback on it before pursuing the idea.

[hdoan741]

I like this proposal. It's kind of like the case with where_not. I think there might be more variations of methods once the query is grouped, and we can add those to this special module.

There are a few things from the Documentation that I'd like to point out:

1. You can write code like this and it would still have to return a __GROUPED relation.

   Student.group(:first_name).where(site_id: 43).count

2. From the documentation, I think the method return type will have to be T::Hash[T.untyped, Integer] thought, because it depends on how many attributes you've groupped

If count is used with Relation#group for multiple columns, it returns a Hash whose keys are an array containing the individual values of each column and the value of each key would be the count.

Article.group(:status, :category).count => {["draft", "business"]=>10, ["draft", "technology"]=>4, ["published", "business"]=>0, ["published", "technology"]=>2}

  sig { returns(T::Hash[String, Integer]) }
  def count; end

[ghiculescu]

1. True. We could fix this by having ActiveRecord_Relation__GROUPED re-define more methods than just count.
2. You're correct; will update proposal. I think T.any(String, T::Array[String]) is ideal.

[hdoan741]

:raise_hands:

On Mon, Feb 24, 2020 at 11:21 AM Alex Ghiculescu notifications@github.com wrote:

1. True. We could fix this by having ActiveRecord_Relation__GROUPED re-define more methods than just count.
2. You're correct; will update proposal.

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