Kaminari pagination is not supported by Tapioca

[lavoiesl]

Trying to update tapioca from 0.12.0 to 0.13.1 results in this error:

path/to/file.rb:32: Method page does not exist on Model::PrivateAssociationRelation https://srb.help/7003
    32 |    @records = Model.all.page(params[:page]).per(25)

Investigation

The page method is defined on the class by kaminari:
https://github.com/kaminari/kaminari/blob/9182d065c144afa45c6b7cf444f810bea1fd7201/kaminari-activerecord/lib/kaminari/activerecord/active_record_model_extension.rb#L14-L23

But attempting to introspect it at runtime yields nothing:

pry(main)> Model.all.method(:page)
=> #<Method: Model::ActiveRecord_Relation#page(*)>
pry(main)> Model.all.method(:page).source_location
=> nil
pry(main)> Model.all.method(:page).owner
=> Model::ActiveRecord_Relation
pry(main)> Model.all.method(:page).owner.instance_method(:page)
NameError: undefined method `page' for class `ActiveRecord::Relation'
from (pry):1:in `instance_method'from (pry):35:in `method'
pry(main)> Model.all.methods.include?(:page)
=> false

This is because it is delegated by https://github.com/rails/rails/blob/d37c533139f70efdcd95f8dadd48c10eba429f94/activerecord/lib/active_record/relation/delegation.rb#L71-L88

Which is generated on demand when the method is missing:
https://github.com/rails/rails/blob/d37c533139f70efdcd95f8dadd48c10eba429f94/activerecord/lib/active_record/relation/delegation.rb#L115-L124

Attempting the same as above after calling the method once does yield something a bit more interesting:

pry(main)> Model.all.method(:page)
=> #<Method: Model::ActiveRecord_Relation(Model::GeneratedRelationMethods)#page(...) /Users/seb/.gem/ruby/3.2.2/gems/activerecord-7.1.3.2/lib/active_record/relation/delegation.rb:78>
pry(main)> Model.all.method(:page).source_location
=> ["/Users/seb/.gem/ruby/3.2.2/gems/activerecord-7.1.3.2/lib/active_record/relation/delegation.rb", 78]
pry(main)> Model.all.method(:page).owner
=> Model::GeneratedRelationMethods
pry(main)> Model.all.method(:page).owner.instance_method(:page)
=> #<UnboundMethod: Model::GeneratedRelationMethods#page(...) /Users/seb/.gem/ruby/3.2.2/gems/activerecord-7.1.3.2/lib/active_record/relation/delegation.rb:78>
pry(main)> Model.all.methods.include?(:page)
=> true

The same can be achieved by calling Model.generate_relation_method(:page)

Workaround

Adding this in config/initializers/kaminari.rb makes tapioca generate the methods:

if defined?(Tapioca)
  Rails.application.config.after_initialize do
    Rails.application.eager_load!

    ActiveRecord::Base.descendants.each do |model|
      model.generate_relation_method(:page)
      model.generate_relation_method(:per)
    end
  end
end

[rzane]

The solution above works pretty well, but it's not aware of methods like #total_count, etc. Here's a compiler that makes the types a bit more accurate. It's based on the ActiveRecordScope compiler, but I took some shortcuts.

I might get around to upstreaming this, but it'd be really cool if someone took it from here.

# typed: ignore

require 'tapioca/dsl/helpers/active_record_constants_helper'
require 'kaminari/activerecord/active_record_model_extension'

module Tapioca
  module Dsl
    module Compilers
      class Kaminari < Tapioca::Dsl::Compiler
        include Tapioca::Dsl::Helpers::ActiveRecordConstantsHelper

        def self.gather_constants
          all_classes
            .select { |c| c < ::Kaminari::ActiveRecordModelExtension }
            .reject(&:abstract_class?)
        end

        def decorate
          root.create_path(constant) do |model|
            generate_page_method(
              model.create_module(RelationMethodsModuleName),
              RelationClassName,
            )

            generate_page_method(
              model.create_module(AssociationRelationMethodsModuleName),
              AssociationRelationClassName,
            )

            model.create_extend(RelationMethodsModuleName)
          end
        end

        private

        def generate_page_method(mod, return_type)
          mod.create_method(
            'page',
            parameters: [create_opt_param('num', type: 'T.any(Integer, String)', default: 'nil')],
            return_type: "T.all(#{return_type}, Kaminari::PageScopeMethods, Kaminari::ActiveRecordRelationMethods)",
          )
        end
      end
    end
  end
end