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Run bundle install and bin/rails db:migrate
Run bin/rails s
Visit http://localhost:3000/posts

The server should stop at the breakpoint:

Started GET "/posts" for 127.0.0.1 at 2022-11-11 18:54:50 +0000
  ActiveRecord::SchemaMigration Pluck (0.2ms)  SELECT "schema_migrations"."version" FROM "schema_migrations" ORDER BY "schema_migrations"."version" ASC
Processing by PostsController#index as HTML
[1, 10] in ~/projects/debug-issue/app/controllers/posts_controller.rb
     1| class PostsController < ApplicationController
     2|   before_action :set_post, only: %i[ show edit update destroy ]
     3|
     4|   # GET /posts or /posts.json
     5|   def index
=>   6|     binding.b
     7|     @posts = Post.all
     8|     a = 1
     9|     b = 2
    10|   end

Type n TWICE, and then the debugger would stop at zeitwerk/kernel.rb while it should stop at a = 1

1st n

(rdbg) n    # next command
[2, 11] in ~/projects/debug-issue/app/controllers/posts_controller.rb
     2|   before_action :set_post, only: %i[ show edit update destroy ]
     3|
     4|   # GET /posts or /posts.json
     5|   def index
     6|     binding.b
=>   7|     @posts = Post.all
     8|     a = 1
     9|     b = 2
    10|   end
    11|
=>#0    PostsController#index at ~/projects/debug-issue/app/controllers/posts_controller.rb:7
  #1    ActionController::BasicImplicitRender#send_action(method="index", args=[]) at ~/.gem/ruby/3.1.2/gems/actionpack-7.0.4/lib/action_controller/metal/basic_implicit_render.rb:6
  # and 76 frames (use `bt' command for all frames)

2nd n

(rdbg) n    # next command
[23, 32] in ~/.gem/ruby/3.1.2/gems/zeitwerk-2.6.6/lib/zeitwerk/kernel.rb
    23|     alias_method :zeitwerk_original_require, :require
    24|   end
    25|
    26|   # @sig (String) -> true | false
    27|   def require(path)
=>  28|     if loader = Zeitwerk::Registry.loader_for(path)
    29|       if path.end_with?(".rb")
    30|         required = zeitwerk_original_require(path)
    31|         loader.on_file_autoloaded(path) if required
    32|         required
=>#0    Kernel#require(path="/Users/hung-wulo/projects/debug-issue/ap...) at ~/.gem/ruby/3.1.2/gems/zeitwerk-2.6.6/lib/zeitwerk/kernel.rb:28
  #1    PostsController#index at ~/projects/debug-issue/app/controllers/posts_controller.rb:7
  # and 77 frames (use `bt' command for all frames)

st0012/debug-issue

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