False positive / conflicting cops: Rails/Delegate and Rails/LexicallyScopedActionFilter?

[tagliala]

Hello,

I don't know if this is actually an issue, but I will report it the same

#912 introduced the ability to delegate to instance variables

In controllers, however, this may conflict with Rails/LexicallyScopedActionFilter, and the developer should take action.

For the moment, I'm undecided on the workaround. I can either:

• disable the delegate on the offending line; or
• explicitly add head :no_content to the controller (but it should be redundant, since it's an API only responding to json and the 204 is the default

---

Expected behavior

Can't tell

Actual behavior

Fixing the Rails/Delegate offense introduces a Rails/LexicallyScopedActionFilter that in order to be fixed should reintroduce the Rails/Delegate offense

Steps to reproduce the problem

Gemfile

# frozen_string_literal: true

source 'https://rubygems.org'

gem 'rubocop', '1.72.1'
gem 'rubocop-rails', '2.30.1'

rubocop.yml

plugins:
  - rubocop-rails

AllCops:
  NewCops: disable

Style/Documentation:
  Enabled: false

app/controllers/posts_controller.rb

# frozen_string_literal: true

class PostsController < ApplicationController
  before_action :set_post, only: %i[destroy]

  def destroy
    @post.destroy
  end

  private

  def set_post
    @post = Post.find(params[:id])
  end
end

First run:

$ rubocop app/controllers/posts_controller.rb 
Inspecting 1 file
C

Offenses:

app/controllers/posts_controller.rb:6:3: C: [Correctable] Rails/Delegate: Use delegate to define delegations.
  def destroy
  ^^^

1 file inspected, 1 offense detected, 1 offense autocorrectable

Second run (with autocorrect)

$ rubocop app/controllers/posts_controller.rb -a
Inspecting 1 file
C

Offenses:

app/controllers/posts_controller.rb:4:3: C: Rails/LexicallyScopedActionFilter: destroy is not explicitly defined on the class.
  before_action :set_post, only: %i[destroy]
  ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
app/controllers/posts_controller.rb:6:3: C: [Corrected] Rails/Delegate: Use delegate to define delegations.
  def destroy
  ^^^

1 file inspected, 2 offenses detected, 1 offense corrected

Third run

$ rubocop app/controllers/posts_controller.rb
Inspecting 1 file
C

Offenses:

app/controllers/posts_controller.rb:4:3: C: Rails/LexicallyScopedActionFilter: destroy is not explicitly defined on the class.
  before_action :set_post, only: %i[destroy]
  ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^

1 file inspected, 1 offense detected

RuboCop version

$ bundle exec rubocop -V
1.72.1 (using Parser 3.3.7.1, rubocop-ast 1.38.0, analyzing as Ruby 2.7, running on ruby 3.4.1) [arm64-darwin24]
  - rubocop-rails 2.30.1