Rails/ActionControllerFlashBeforeRender reports false positives with if/else and redirect_to

[tagliala]

RuboCop reports a false positive with if/else and redirect_to

Follow up from #812 (comment)

---

Expected behavior

Rubocop does not report errors

Actual behavior

Inspecting 1 file
C

Offenses:

pages_controller.rb:6:7: C: [Correctable] Rails/ActionControllerFlashBeforeRender: Use flash.now before render.
      flash[:success] = t('.flash.success') # false positive
      ^^^^^
pages_controller.rb:17:7: C: [Correctable] Rails/ActionControllerFlashBeforeRender: Use flash.now before render.
      flash[:notice] = t('.flash.notice') # false positive
      ^^^^^
pages_controller.rb:25:7: C: [Correctable] Rails/ActionControllerFlashBeforeRender: Use flash.now before render.
      flash[:success] = t('.flash.success') # false positive
      ^^^^^
pages_controller.rb:27:7: C: [Correctable] Rails/ActionControllerFlashBeforeRender: Use flash.now before render.
      flash[:alert] = t('.flash.fail') # false positive
      ^^^^^

1 file inspected, 4 offenses detected, 4 offenses autocorrectable

Steps to reproduce the problem

1. Create the following pages_controller.rb file

# frozen_string_literal: true

class PagesController < ApplicationController
  def update
    if @page.save
      flash[:success] = t('.flash.success') # false positive
    else
      flash.now[:alert] = t('.flash.fail')
      render 'edit'
    end

    redirect_to @page
  end

  def dismiss
    if @something
      flash[:notice] = t('.flash.notice') # false positive
    end

    redirect_to pages_path
  end

  def destroy
    if @page.destroy
      flash[:success] = t('.flash.success') # false positive
    else
      flash[:alert] = t('.flash.fail') # false positive
    end

    redirect_to pages_path
  end
end

2. Run rubocop --require rubocop-rails --only Rails/ActionControllerFlashBeforeRender pages_controller.rb

RuboCop version

$ rubocop --require rubocop-rails -V
1.37.0 (using Parser 3.1.2.1, rubocop-ast 1.23.0, running on ruby 3.1.2) [x86_64-darwin21]
  - rubocop-rails 2.17.0

Also tested against rubocop-rails main

[mockdeep]

We're seeing the same issue when we use redirect_back.

[tagliala]

Hi, I've tested 2.17.2 but there are still false positives. As far as I can tell, some of them are not easy to detect and also providing a reduced test case is tricky

I've started with #843