Set up until "rails new" execution

```
mkdir ./avoid_losing_extensibility_with_webpacker
cd ./avoid_losing_extensibility_with_webpacker
bundle init
vi Gemfile  # Uncomment 'gem "rails"' row.
bundle install
bundle exec rails new . --webpack --skip-turbolinks
```

.browserslistrc

@@ -0,0 +1 @@
+defaults

.gitattributes

@@ -0,0 +1,10 @@
+# See https://git-scm.com/docs/gitattributes for more about git attribute files.
+
+# Mark the database schema as having been generated.
+db/schema.rb linguist-generated
+
+# Mark the yarn lockfile as having been generated.
+yarn.lock linguist-generated
+
+# Mark any vendored files as having been vendored.
+vendor/* linguist-vendored

.gitignore

@@ -0,0 +1,40 @@
+# See https://help.github.com/articles/ignoring-files for more about ignoring files.
+#
+# If you find yourself ignoring temporary files generated by your text editor
+# or operating system, you probably want to add a global ignore instead:
+#   git config --global core.excludesfile '~/.gitignore_global'
+
+# Ignore bundler config.
+/.bundle
+
+# Ignore the default SQLite database.
+/db/*.sqlite3
+/db/*.sqlite3-*
+
+# Ignore all logfiles and tempfiles.
+/log/*
+/tmp/*
+!/log/.keep
+!/tmp/.keep
+
+# Ignore pidfiles, but keep the directory.
+/tmp/pids/*
+!/tmp/pids/
+!/tmp/pids/.keep
+
+# Ignore uploaded files in development.
+/storage/*
+!/storage/.keep
+
+/public/assets
+.byebug_history
+
+# Ignore master key for decrypting credentials and more.
+/config/master.key
+
+/public/packs
+/public/packs-test
+/node_modules
+/yarn-error.log
+yarn-debug.log*
+.yarn-integrity

Gemfile

@@ -0,0 +1,54 @@
+source 'https://rubygems.org'
+git_source(:github) { |repo| "https://github.com/#{repo}.git" }
+
+ruby '2.7.1'
+
+# Bundle edge Rails instead: gem 'rails', github: 'rails/rails'
+gem 'rails', '~> 6.1.0'
+# Use sqlite3 as the database for Active Record
+gem 'sqlite3', '~> 1.4'
+# Use Puma as the app server
+gem 'puma', '~> 5.0'
+# Use SCSS for stylesheets
+gem 'sass-rails', '>= 6'
+# Transpile app-like JavaScript. Read more: https://github.com/rails/webpacker
+gem 'webpacker', '~> 5.0'
+# Build JSON APIs with ease. Read more: https://github.com/rails/jbuilder
+gem 'jbuilder', '~> 2.7'
+# Use Redis adapter to run Action Cable in production
+# gem 'redis', '~> 4.0'
+# Use Active Model has_secure_password
+# gem 'bcrypt', '~> 3.1.7'
+
+# Use Active Storage variant
+# gem 'image_processing', '~> 1.2'
+
+# Reduces boot times through caching; required in config/boot.rb
+gem 'bootsnap', '>= 1.4.4', require: false
+
+group :development, :test do
+  # Call 'byebug' anywhere in the code to stop execution and get a debugger console
+  gem 'byebug', platforms: [:mri, :mingw, :x64_mingw]
+end
+
+group :development do
+  # Access an interactive console on exception pages or by calling 'console' anywhere in the code.
+  gem 'web-console', '>= 4.1.0'
+  # Display performance information such as SQL time and flame graphs for each request in your browser.
+  # Can be configured to work on production as well see: https://github.com/MiniProfiler/rack-mini-profiler/blob/master/README.md
+  gem 'rack-mini-profiler', '~> 2.0'
+  gem 'listen', '~> 3.3'
+  # Spring speeds up development by keeping your application running in the background. Read more: https://github.com/rails/spring
+  gem 'spring'
+end
+
+group :test do
+  # Adds support for Capybara system testing and selenium driver
+  gem 'capybara', '>= 3.26'
+  gem 'selenium-webdriver'
+  # Easy installation and use of web drivers to run system tests with browsers
+  gem 'webdrivers'
+end
+
+# Windows does not include zoneinfo files, so bundle the tzinfo-data gem
+gem 'tzinfo-data', platforms: [:mingw, :mswin, :x64_mingw, :jruby]

Gemfile.lock

@@ -0,0 +1,223 @@
+GEM
+  remote: https://rubygems.org/
+  specs:
+    actioncable (6.1.0)
+      actionpack (= 6.1.0)
+      activesupport (= 6.1.0)
+      nio4r (~> 2.0)
+      websocket-driver (>= 0.6.1)
+    actionmailbox (6.1.0)
+      actionpack (= 6.1.0)
+      activejob (= 6.1.0)
+      activerecord (= 6.1.0)
+      activestorage (= 6.1.0)
+      activesupport (= 6.1.0)
+      mail (>= 2.7.1)
+    actionmailer (6.1.0)
+      actionpack (= 6.1.0)
+      actionview (= 6.1.0)
+      activejob (= 6.1.0)
+      activesupport (= 6.1.0)
+      mail (~> 2.5, >= 2.5.4)
+      rails-dom-testing (~> 2.0)
+    actionpack (6.1.0)
+      actionview (= 6.1.0)
+      activesupport (= 6.1.0)
+      rack (~> 2.0, >= 2.0.9)
+      rack-test (>= 0.6.3)
+      rails-dom-testing (~> 2.0)
+      rails-html-sanitizer (~> 1.0, >= 1.2.0)
+    actiontext (6.1.0)
+      actionpack (= 6.1.0)
+      activerecord (= 6.1.0)
+      activestorage (= 6.1.0)
+      activesupport (= 6.1.0)
+      nokogiri (>= 1.8.5)
+    actionview (6.1.0)
+      activesupport (= 6.1.0)
+      builder (~> 3.1)
+      erubi (~> 1.4)
+      rails-dom-testing (~> 2.0)
+      rails-html-sanitizer (~> 1.1, >= 1.2.0)
+    activejob (6.1.0)
+      activesupport (= 6.1.0)
+      globalid (>= 0.3.6)
+    activemodel (6.1.0)
+      activesupport (= 6.1.0)
+    activerecord (6.1.0)
+      activemodel (= 6.1.0)
+      activesupport (= 6.1.0)
+    activestorage (6.1.0)
+      actionpack (= 6.1.0)
+      activejob (= 6.1.0)
+      activerecord (= 6.1.0)
+      activesupport (= 6.1.0)
+      marcel (~> 0.3.1)
+      mimemagic (~> 0.3.2)
+    activesupport (6.1.0)
+      concurrent-ruby (~> 1.0, >= 1.0.2)
+      i18n (>= 1.6, < 2)
+      minitest (>= 5.1)
+      tzinfo (~> 2.0)
+      zeitwerk (~> 2.3)
+    addressable (2.7.0)
+      public_suffix (>= 2.0.2, < 5.0)
+    bindex (0.8.1)
+    bootsnap (1.5.1)
+      msgpack (~> 1.0)
+    builder (3.2.4)
+    byebug (11.1.3)
+    capybara (3.34.0)
+      addressable
+      mini_mime (>= 0.1.3)
+      nokogiri (~> 1.8)
+      rack (>= 1.6.0)
+      rack-test (>= 0.6.3)
+      regexp_parser (~> 1.5)
+      xpath (~> 3.2)
+    childprocess (3.0.0)
+    concurrent-ruby (1.1.7)
+    crass (1.0.6)
+    erubi (1.10.0)
+    ffi (1.13.1)
+    globalid (0.4.2)
+      activesupport (>= 4.2.0)
+    i18n (1.8.5)
+      concurrent-ruby (~> 1.0)
+    jbuilder (2.10.1)
+      activesupport (>= 5.0.0)
+    listen (3.3.3)
+      rb-fsevent (~> 0.10, >= 0.10.3)
+      rb-inotify (~> 0.9, >= 0.9.10)
+    loofah (2.8.0)
+      crass (~> 1.0.2)
+      nokogiri (>= 1.5.9)
+    mail (2.7.1)
+      mini_mime (>= 0.1.1)
+    marcel (0.3.3)
+      mimemagic (~> 0.3.2)
+    method_source (1.0.0)
+    mimemagic (0.3.5)
+    mini_mime (1.0.2)
+    mini_portile2 (2.4.0)
+    minitest (5.14.2)
+    msgpack (1.3.3)
+    nio4r (2.5.4)
+    nokogiri (1.10.10)
+      mini_portile2 (~> 2.4.0)
+    public_suffix (4.0.6)
+    puma (5.1.1)
+      nio4r (~> 2.0)
+    rack (2.2.3)
+    rack-mini-profiler (2.2.0)
+      rack (>= 1.2.0)
+    rack-proxy (0.6.5)
+      rack
+    rack-test (1.1.0)
+      rack (>= 1.0, < 3)
+    rails (6.1.0)
+      actioncable (= 6.1.0)
+      actionmailbox (= 6.1.0)
+      actionmailer (= 6.1.0)
+      actionpack (= 6.1.0)
+      actiontext (= 6.1.0)
+      actionview (= 6.1.0)
+      activejob (= 6.1.0)
+      activemodel (= 6.1.0)
+      activerecord (= 6.1.0)
+      activestorage (= 6.1.0)
+      activesupport (= 6.1.0)
+      bundler (>= 1.15.0)
+      railties (= 6.1.0)
+      sprockets-rails (>= 2.0.0)
+    rails-dom-testing (2.0.3)
+      activesupport (>= 4.2.0)
+      nokogiri (>= 1.6)
+    rails-html-sanitizer (1.3.0)
+      loofah (~> 2.3)
+    railties (6.1.0)
+      actionpack (= 6.1.0)
+      activesupport (= 6.1.0)
+      method_source
+      rake (>= 0.8.7)
+      thor (~> 1.0)
+    rake (13.0.1)
+    rb-fsevent (0.10.4)
+    rb-inotify (0.10.1)
+      ffi (~> 1.0)
+    regexp_parser (1.8.2)
+    rubyzip (2.3.0)
+    sass-rails (6.0.0)
+      sassc-rails (~> 2.1, >= 2.1.1)
+    sassc (2.4.0)
+      ffi (~> 1.9)
+    sassc-rails (2.1.2)
+      railties (>= 4.0.0)
+      sassc (>= 2.0)
+      sprockets (> 3.0)
+      sprockets-rails
+      tilt
+    selenium-webdriver (3.142.7)
+      childprocess (>= 0.5, < 4.0)
+      rubyzip (>= 1.2.2)
+    semantic_range (2.3.1)
+    spring (2.1.1)
+    sprockets (4.0.2)
+      concurrent-ruby (~> 1.0)
+      rack (> 1, < 3)
+    sprockets-rails (3.2.2)
+      actionpack (>= 4.0)
+      activesupport (>= 4.0)
+      sprockets (>= 3.0.0)
+    sqlite3 (1.4.2)
+    thor (1.0.1)
+    tilt (2.0.10)
+    tzinfo (2.0.4)
+      concurrent-ruby (~> 1.0)
+    web-console (4.1.0)
+      actionview (>= 6.0.0)
+      activemodel (>= 6.0.0)
+      bindex (>= 0.4.0)
+      railties (>= 6.0.0)
+    webdrivers (4.4.1)
+      nokogiri (~> 1.6)
+      rubyzip (>= 1.3.0)
+      selenium-webdriver (>= 3.0, < 4.0)
+    webpacker (5.2.1)
+      activesupport (>= 5.2)
+      rack-proxy (>= 0.6.1)
+      railties (>= 5.2)
+      semantic_range (>= 2.3.0)
+    websocket-driver (0.7.3)
+      websocket-extensions (>= 0.1.0)
+    websocket-extensions (0.1.5)
+    xpath (3.2.0)
+      nokogiri (~> 1.8)
+    zeitwerk (2.4.2)
+
+PLATFORMS
+  x86_64-darwin-19
+
+DEPENDENCIES
+  bootsnap (>= 1.4.4)
+  byebug
+  capybara (>= 3.26)
+  jbuilder (~> 2.7)
+  listen (~> 3.3)
+  puma (~> 5.0)
+  rack-mini-profiler (~> 2.0)
+  rails (~> 6.1.0)
+  sass-rails (>= 6)
+  selenium-webdriver
+  spring
+  sqlite3 (~> 1.4)
+  tzinfo-data
+  web-console (>= 4.1.0)
+  webdrivers
+  webpacker (~> 5.0)
+
+RUBY VERSION
+   ruby 2.7.1p83
+
+BUNDLED WITH
+   2.2.1

README.md

@@ -0,0 +1,24 @@
+# README
+
+This README would normally document whatever steps are necessary to get the
+application up and running.
+
+Things you may want to cover:
+
+* Ruby version
+
+* System dependencies
+
+* Configuration
+
+* Database creation
+
+* Database initialization
+
+* How to run the test suite
+
+* Services (job queues, cache servers, search engines, etc.)
+
+* Deployment instructions
+
+* ...

Rakefile

@@ -0,0 +1,6 @@
+# Add your own tasks in files placed in lib/tasks ending in .rake,
+# for example lib/tasks/capistrano.rake, and they will automatically be available to Rake.
+
+require_relative "config/application"
+
+Rails.application.load_tasks

app/assets/config/manifest.js

@@ -0,0 +1,2 @@
+//= link_tree ../images
+//= link_directory ../stylesheets .css

app/assets/stylesheets/application.css

@@ -0,0 +1,15 @@
+/*
+ * This is a manifest file that'll be compiled into application.css, which will include all the files
+ * listed below.
+ *
+ * Any CSS and SCSS file within this directory, lib/assets/stylesheets, or any plugin's
+ * vendor/assets/stylesheets directory can be referenced here using a relative path.
+ *
+ * You're free to add application-wide styles to this file and they'll appear at the bottom of the
+ * compiled file so the styles you add here take precedence over styles defined in any other CSS/SCSS
+ * files in this directory. Styles in this file should be added after the last require_* statement.
+ * It is generally better to create a new file per style scope.
+ *
+ *= require_tree .
+ *= require_self
+ */

app/channels/application_cable/channel.rb

@@ -0,0 +1,4 @@
+module ApplicationCable
+  class Channel < ActionCable::Channel::Base
+  end
+end

app/channels/application_cable/connection.rb

@@ -0,0 +1,4 @@
+module ApplicationCable
+  class Connection < ActionCable::Connection::Base
+  end
+end

app/controllers/application_controller.rb

@@ -0,0 +1,2 @@
+class ApplicationController < ActionController::Base
+end

app/helpers/application_helper.rb

@@ -0,0 +1,2 @@
+module ApplicationHelper
+end