Make Webpacker the default JavaScript compiler for Rails 6 (#33079)

* Use Webpacker by default on new apps

* Stop including coffee-rails by default

* Drop using a js_compressor by default

* Drop extra test for coffeescript inclusion by default

* Stick with skip_javascript to signify skipping webpack

* Don't install a JS runtime by default any more

* app/javascript will be the new default directory for JS

* Make it clear that this is just for configuring the default Webpack framework setup now

* Start using the Webpack tag in the default layout

* Irrelevant test

* jQuery is long gone

* Stop having asset pipeline compile default application.js

* Add rails-ujs by default to the Webpack setup

* Add Active Storage JavaScript to application.js pack by default

* Consistent quoting

* Add Turbolinks to default pack

* Add Action Cable to default pack

Need some work on how to set the global consumer that channels will
work with. @javan?

* Require all channels by default and use a separate consumer stub

* Channel generator now targets Webpack style

* Update task docs to match new generator style

* Use uniform import style

* Drop the JS assets generator

It was barely helpful as it was. It’s no longer helpful in a Webpacked
world. Sayonara!

* Add app/javascript to the stats directories

* Simpler import style

Which match the other imports.

* Address test failures from dropping JS compilation (and compression)

* webpacker-default: Modify `AssetsGeneratorTest`

Before:

```
$ bin/test test/generators/assets_generator_test.rb
Run options: --seed 46201

F

Failure:
AssetsGeneratorTest#test_assets [/Users/ttanimichi/ghq/github.com/ttanimichi/rails/railties/test/generators/assets_generator_test.rb:12]:
Expected file "app/assets/javascripts/posts.js" to exist, but does not

bin/test /Users/ttanimichi/ghq/github.com/ttanimichi/rails/railties/test/generators/assets_generator_test.rb:10

.

Finished in 0.031343s, 63.8101 runs/s, 95.7152 assertions/s.
2 runs, 3 assertions, 1 failures, 0 errors, 0 skips
```

After:

```
$ bin/test test/generators/assets_generator_test.rb
Run options: --seed 43571

..

Finished in 0.030370s, 65.8545 runs/s, 65.8545 assertions/s.
2 runs, 2 assertions, 0 failures, 0 errors, 0 skips
```

* webpacker-default: Modify `ChannelGeneratorTest`

Before:

```
$ bin/test test/generators/channel_generator_test.rb
Run options: --seed 8986

.F

Failure:
ChannelGeneratorTest#test_channel_with_multiple_actions_is_created [/Users/ttanimichi/ghq/github.com/ttanimichi/rails/railties/test/generators/channel_generator_test.rb:43]:
Expected file "app/assets/javascripts/channels/chat.js" to exist, but does not

bin/test /Users/ttanimichi/ghq/github.com/ttanimichi/rails/railties/test/generators/channel_generator_test.rb:34

.F

Failure:
ChannelGeneratorTest#test_channel_is_created [/Users/ttanimichi/ghq/github.com/ttanimichi/rails/railties/test/generators/channel_generator_test.rb:29]:
Expected file "app/assets/javascripts/channels/chat.js" to exist, but does not

bin/test /Users/ttanimichi/ghq/github.com/ttanimichi/rails/railties/test/generators/channel_generator_test.rb:22

E

Error:
ChannelGeneratorTest#test_cable_js_is_created_if_not_present_already:
Errno::ENOENT: No such file or directory @ apply2files - /Users/ttanimichi/ghq/github.com/ttanimichi/rails/railties/test/fixtures/tmp/app/assets/javascripts/cable.js

bin/test /Users/ttanimichi/ghq/github.com/ttanimichi/rails/railties/test/generators/channel_generator_test.rb:60

F

Failure:
ChannelGeneratorTest#test_channel_suffix_is_not_duplicated [/Users/ttanimichi/ghq/github.com/ttanimichi/rails/railties/test/generators/channel_generator_test.rb:87]:
Expected file "app/assets/javascripts/channels/chat.js" to exist, but does not

bin/test /Users/ttanimichi/ghq/github.com/ttanimichi/rails/railties/test/generators/channel_generator_test.rb:80

F

Failure:
ChannelGeneratorTest#test_channel_on_revoke [/Users/ttanimichi/ghq/github.com/ttanimichi/rails/railties/test/generators/channel_generator_test.rb:77]:
Expected file "app/assets/javascripts/cable.js" to exist, but does not

bin/test /Users/ttanimichi/ghq/github.com/ttanimichi/rails/railties/test/generators/channel_generator_test.rb:68

Finished in 0.064384s, 108.7227 runs/s, 481.4861 assertions/s.
7 runs, 31 assertions, 4 failures, 1 errors, 0 skips
```

After:

```
$ bin/test test/generators/channel_generator_test.rb
Run options: --seed 44857

.......

Finished in 0.060243s, 116.1961 runs/s, 697.1764 assertions/s.
7 runs, 42 assertions, 0 failures, 0 errors, 0 skips
```

* Fix shared generator tests.

* webpacker-default: Modify `ControllerGeneratorTest`

The JS assets generator was dropped. ref. https://github.com/rails/rails/commit/46215b179483d3e4d264555f5a4952f43eb8142a

* Revert "Simpler import style". It's currently failing with an error of "TypeError: undefined is not an object (evaluating '__WEBPACK_IMPORTED_MODULE_2_activestorage___default.a.start')". Waiting for @javan to have a look.

This reverts commit 5d3ebb71059f635d3756cbda4ab9752027e09256.

* require webpacker in test app

* Add webpacker without making the build hang/timeout. (#33640)

* use yarn workspaces to allow for installing unreleased packages and only generate js/bootsnap when required

* no longer need to have webpacker in env templates as webpacker moved this config to yml file

* Fix rubocop violation

* Got the test passing for the running scaffold

* update expected lines of code

* update middleware tests to account for webpacker

* disable js in plugins be default to get the tests passing (#34009)

* clear codeclimate report issues

* Anything newer than currently released is good

* Use Webpacker development version during development of Rails

* Edge should get development webpacker as well

* Add changelog entry for Webpacker change

49 files changed, 285 insertions, 327 deletions

diff --git a/.gitignore b/.gitignore
index ab9ca8a6ac..d44875ed9a 100644
--- a/.gitignore
+++ b/.gitignore
@@ -14,3 +14,5 @@ debug.log
 node_modules/
 package-lock.json
 pkg/
+/tmp/
+/yarn.lock
\ No newline at end of file
diff --git a/.travis.yml b/.travis.yml
index 109005b407..7dc6360e73 100644
--- a/.travis.yml
+++ b/.travis.yml
@@ -42,6 +42,11 @@ before_install:
   - "[[ $GEM != 'av:ujs' ]] || nvm install node"
   - "[[ $GEM != 'av:ujs' ]] || node --version"
   - "[[ $GEM != 'av:ujs' ]] || (cd actionview && npm install)"
+  - "[[ $GEM != 'ar:mysql2' ]] || [[ $MYSQL == 'mariadb' ]] || sudo mysql -e \"use mysql; update user set authentication_string='' where User='root'; update user set plugin='mysql_native_password';FLUSH PRIVILEGES;\""
+  - "[[ $GEM != 'ar:mysql2' ]] || [[ $MYSQL == 'mariadb' ]] || sudo mysql_upgrade"
+  - "[[ $GEM != 'ar:mysql2' ]] || [[ $MYSQL == 'mariadb' ]] || sudo service mysql restart"
+  - "[[ $GEM != 'railties' ]] || (curl -o- -L https://yarnpkg.com/install.sh | bash)"
+  - "[[ $GEM != 'railties' ]] || export PATH=$HOME/.yarn/bin:$PATH"
 
 before_script:
   # Set Sauce Labs username and access key. Obfuscated, purposefully not encrypted.
diff --git a/.yarnrc b/.yarnrc
new file mode 100644
index 0000000000..6be74e145d
--- /dev/null
+++ b/.yarnrc
@@ -0,0 +1,2 @@
+workspaces-experimental true
+--add.prefer-offline true
\ No newline at end of file
diff --git a/Gemfile b/Gemfile
index 5bf443b7c8..c35254eb43 100644
--- a/Gemfile
+++ b/Gemfile
@@ -15,7 +15,7 @@ gem "rack-cache", "~> 1.2"
 gem "coffee-rails"
 gem "sass-rails"
 gem "turbolinks", "~> 5"
-
+gem "webpacker", github: "rails/webpacker", require: ENV["SKIP_REQUIRE_WEBPACKER"] != "true"
 # require: false so bcrypt is loaded only when has_secure_password is used.
 # This is to avoid Active Model (and by extension the entire framework)
 # being dependent on a binary library.
diff --git a/Gemfile.lock b/Gemfile.lock
index e6fc04b5ca..dfa38ed102 100644
--- a/Gemfile.lock
+++ b/Gemfile.lock
@@ -30,6 +30,15 @@ GIT
     queue_classic (3.2.0.RC1)
       pg (>= 0.17, < 2.0)
 
+GIT
+  remote: https://github.com/rails/webpacker.git
+  revision: 48d9fd52c3e9637dbb21e551b48c84c0f2dbb2ed
+  specs:
+    webpacker (4.0.0.pre.pre.2)
+      activesupport (>= 4.2)
+      rack-proxy (>= 0.6.1)
+      railties (>= 4.2)
+
 PATH
   remote: .
   specs:
@@ -364,6 +373,8 @@ GEM
       rack (>= 0.4)
     rack-protection (2.0.3)
       rack
+    rack-proxy (0.6.5)
+      rack
     rack-test (1.1.0)
       rack (>= 1.0, < 3)
     rails-dom-testing (2.0.3)
@@ -565,6 +576,7 @@ DEPENDENCIES
   uglifier (>= 1.3.0)
   w3c_validators
   wdm (>= 0.1.0)
+  webpacker!
   websocket-client-simple!
 
 BUNDLED WITH
diff --git a/actioncable/lib/rails/generators/channel/USAGE b/actioncable/lib/rails/generators/channel/USAGE
index dd109fda80..ea9662436c 100644
--- a/actioncable/lib/rails/generators/channel/USAGE
+++ b/actioncable/lib/rails/generators/channel/USAGE
@@ -1,14 +1,12 @@
 Description:
 ============
-    Stubs out a new cable channel for the server (in Ruby) and client (in CoffeeScript).
+    Stubs out a new cable channel for the server (in Ruby) and client (in JavaScript).
     Pass the channel name, either CamelCased or under_scored, and an optional list of channel actions as arguments.
 
-    Note: Turn on the cable connection in app/assets/javascripts/cable.js after generating any channels.
-
 Example:
 ========
     rails generate channel Chat speak
 
-    creates a Chat channel class and CoffeeScript asset:
+    creates a Chat channel class and JavaScript asset:
         Channel:    app/channels/chat_channel.rb
-        Assets:     app/assets/javascripts/channels/chat.coffee
+        Assets:     app/javascript/channels/chat_channel.js
diff --git a/actioncable/lib/rails/generators/channel/channel_generator.rb b/actioncable/lib/rails/generators/channel/channel_generator.rb
index 427eef1f55..ef51981e89 100644
--- a/actioncable/lib/rails/generators/channel/channel_generator.rb
+++ b/actioncable/lib/rails/generators/channel/channel_generator.rb
@@ -16,10 +16,11 @@ module Rails
 
         if options[:assets]
           if behavior == :invoke
-            template "assets/cable.js", "app/assets/javascripts/cable.js"
+            template "javascript/index.js", "app/javascript/channels/index.js"
+            template "javascript/consumer.js", "app/javascript/channels/consumer.js"
           end
 
-          js_template "assets/channel", File.join("app/assets/javascripts/channels", class_path, "#{file_name}")
+          js_template "javascript/channel", File.join("app/javascript/channels", class_path, "#{file_name}_channel")
         end
 
         generate_application_cable_files
diff --git a/actioncable/lib/rails/generators/channel/templates/assets/channel.coffee.tt b/actioncable/lib/rails/generators/channel/templates/assets/channel.coffee.tt
deleted file mode 100644
index 5467811aba..0000000000
--- a/actioncable/lib/rails/generators/channel/templates/assets/channel.coffee.tt
+++ /dev/null
@@ -1,14 +0,0 @@
-App.<%= class_name.underscore %> = App.cable.subscriptions.create "<%= class_name %>Channel",
-  connected: ->
-    # Called when the subscription is ready for use on the server
-
-  disconnected: ->
-    # Called when the subscription has been terminated by the server
-
-  received: (data) ->
-    # Called when there's incoming data on the websocket for this channel
-<% actions.each do |action| -%>
-
-  <%= action %>: ->
-    @perform '<%= action %>'
-<% end -%>
diff --git a/actioncable/lib/rails/generators/channel/templates/assets/channel.js.tt b/actioncable/lib/rails/generators/channel/templates/javascript/channel.js.tt
index ab0e68b11a..33baaa5a22 100644
--- a/actioncable/lib/rails/generators/channel/templates/assets/channel.js.tt
+++ b/actioncable/lib/rails/generators/channel/templates/javascript/channel.js.tt
@@ -1,4 +1,6 @@
-App.<%= class_name.underscore %> = App.cable.subscriptions.create("<%= class_name %>Channel", {
+import consumer from "./consumer"
+
+consumer.subscriptions.create("<%= class_name %>Channel", {
   connected: function() {
     // Called when the subscription is ready for use on the server
   },
diff --git a/actioncable/lib/rails/generators/channel/templates/assets/cable.js.tt b/actioncable/lib/rails/generators/channel/templates/javascript/consumer.js.tt
index 739aa5f022..76ca3d0f2f 100644
--- a/actioncable/lib/rails/generators/channel/templates/assets/cable.js.tt
+++ b/actioncable/lib/rails/generators/channel/templates/javascript/consumer.js.tt
@@ -1,13 +1,6 @@
 // Action Cable provides the framework to deal with WebSockets in Rails.
 // You can generate new channels where WebSocket features live using the `rails generate channel` command.
-//
-//= require action_cable
-//= require_self
-//= require_tree ./channels
 
-(function() {
-  this.App || (this.App = {});
+import ActionCable from "actioncable"
 
-  App.cable = ActionCable.createConsumer();
-
-}).call(this);
+export default ActionCable.createConsumer()
diff --git a/actioncable/lib/rails/generators/channel/templates/javascript/index.js.tt b/actioncable/lib/rails/generators/channel/templates/javascript/index.js.tt
new file mode 100644
index 0000000000..5da1ce2dce
--- /dev/null
+++ b/actioncable/lib/rails/generators/channel/templates/javascript/index.js.tt
@@ -0,0 +1,5 @@
+// Load all the channels within this directory and all subdirectories. 
+// Channel files must be named *_channel.js.
+
+const channels = require.context('.', true, /\_channel\.js$/)
+channels.keys().forEach(channels)
diff --git a/activestorage/test/dummy/app/assets/config/manifest.js b/activestorage/test/dummy/app/assets/config/manifest.js
index a8adebe722..bb109908b2 100644
--- a/activestorage/test/dummy/app/assets/config/manifest.js
+++ b/activestorage/test/dummy/app/assets/config/manifest.js
@@ -1,5 +1,3 @@
 
 //= link_tree ../images
-//= link_directory ../javascripts .js
 //= link_directory ../stylesheets .css
-//= link active_storage_manifest.js
diff --git a/activestorage/test/dummy/config/environments/production.rb b/activestorage/test/dummy/config/environments/production.rb
index 34ac3bc561..be7f5b80d4 100644
--- a/activestorage/test/dummy/config/environments/production.rb
+++ b/activestorage/test/dummy/config/environments/production.rb
@@ -25,8 +25,7 @@ Rails.application.configure do
   # Apache or NGINX already handles this.
   config.public_file_server.enabled = ENV["RAILS_SERVE_STATIC_FILES"].present?
 
-  # Compress JavaScripts and CSS.
-  config.assets.js_compressor = :uglifier
+  # Compress CSS using a preprocessor.
   # config.assets.css_compressor = :sass
 
   # Do not fallback to assets pipeline if a precompiled asset is missed.
diff --git a/activestorage/test/dummy/config/webpacker.yml b/activestorage/test/dummy/config/webpacker.yml
new file mode 100644
index 0000000000..c1515a2e95
--- /dev/null
+++ b/activestorage/test/dummy/config/webpacker.yml
@@ -0,0 +1,72 @@
+# Note: You must restart bin/webpack-dev-server for changes to take effect
+
+default: &default
+  source_path: app/javascript
+  source_entry_path: packs
+  public_output_path: packs
+  cache_path: tmp/cache/webpacker
+  check_yarn_integrity: false
+
+  # Additional paths webpack should lookup modules
+  # ['app/assets', 'engine/foo/app/assets']
+  resolved_paths: []
+
+  # Reload manifest.json on all requests so we reload latest compiled packs
+  cache_manifest: false
+
+  extensions:
+    - .js
+    - .sass
+    - .scss
+    - .css
+    - .module.sass
+    - .module.scss
+    - .module.css
+    - .png
+    - .svg
+    - .gif
+    - .jpeg
+    - .jpg
+
+development:
+  <<: *default
+  compile: true
+
+  # Verifies that versions and hashed value of the package contents in the project's package.json
+  check_yarn_integrity: true
+
+  # Reference: https://webpack.js.org/configuration/dev-server/
+  dev_server:
+    https: false
+    host: localhost
+    port: 3035
+    public: localhost:3035
+    hmr: false
+    # Inline should be set to true if using HMR
+    inline: true
+    overlay: true
+    compress: true
+    disable_host_check: true
+    use_local_ip: false
+    quiet: false
+    headers:
+      'Access-Control-Allow-Origin': '*'
+    watch_options:
+      ignored: /node_modules/
+
+
+test:
+  <<: *default
+  compile: true
+
+  # Compile test packs to a separate directory
+  public_output_path: packs-test
+
+production:
+  <<: *default
+
+  # Production depends on precompilation of packs prior to booting for performance.
+  compile: false
+
+  # Cache manifest.json for performance
+  cache_manifest: true
diff --git a/package.json b/package.json
new file mode 100644
index 0000000000..88029de141
--- /dev/null
+++ b/package.json
@@ -0,0 +1,14 @@
+{
+  "private": true,
+  "workspaces": [
+    "actioncable",
+    "activestorage",
+    "actionview",
+    "tmp/templates/app_template",
+    "railties/test/fixtures/tmp/bukkits/**/test/dummy",
+    "railties/test/fixtures/tmp/bukkits/**/spec/dummy"
+  ],
+  "dependencies": {
+    "webpack": "^4.17.1"
+  }
+}
diff --git a/railties/CHANGELOG.md b/railties/CHANGELOG.md
index 37444c4cf6..925dac7b3c 100644
--- a/railties/CHANGELOG.md
+++ b/railties/CHANGELOG.md
@@ -1,3 +1,11 @@
+*   Use Webpacker by default to manage app-level JavaScript through the new app/javascript directory.
+    Sprockets is now solely in charge, by default, of compiling CSS and other static assets.
+    Action Cable channel generators will create ES6 stubs rather than use CoffeeScript.
+    Active Storage, Action Cable, Turbolinks, and Rails-UJS are loaded by a new application.js pack.
+    Generators no longer generate JavaScript stubs.
+
+    *DHH*, *Lachlan Sylvester*
+
 *   Refactors `migrations_paths` command option in generators
     to `database` (aliased as `db`). Now, the migrations paths
     will be read from the specified database configuration in the
diff --git a/railties/Rakefile b/railties/Rakefile
index e1be0ceb40..445f6217b3 100644
--- a/railties/Rakefile
+++ b/railties/Rakefile
@@ -28,6 +28,9 @@ namespace :test do
     require "bundler/setup" unless defined?(Bundler)
     require "active_support"
 
+    # Only generate the template app once.
+    require_relative "test/isolation/abstract_unit"
+
     failing_files = []
 
     dirs = (ENV["TEST_DIR"] || ENV["TEST_DIRS"] || "**").split(",")
diff --git a/railties/lib/rails/generators.rb b/railties/lib/rails/generators.rb
index ed672ae48e..cd8f16e247 100644
--- a/railties/lib/rails/generators.rb
+++ b/railties/lib/rails/generators.rb
@@ -33,8 +33,6 @@ module Rails
       rails: {
         actions: "-a",
         orm: "-o",
-        javascripts: "-j",
-        javascript_engine: "-je",
         resource_controller: "-c",
         scaffold_controller: "-c",
         stylesheets: "-y",
diff --git a/railties/lib/rails/generators/app_base.rb b/railties/lib/rails/generators/app_base.rb
index 8991c547ca..410e53b4c0 100644
--- a/railties/lib/rails/generators/app_base.rb
+++ b/railties/lib/rails/generators/app_base.rb
@@ -68,10 +68,7 @@ module Rails
         class_option :skip_listen,         type: :boolean, default: false,
                                            desc: "Don't generate configuration that depends on the listen gem"
 
-        class_option :skip_coffee,         type: :boolean, default: false,
-                                           desc: "Don't use CoffeeScript"
-
-        class_option :skip_javascript,     type: :boolean, aliases: "-J", default: false,
+        class_option :skip_javascript,     type: :boolean, aliases: "-J", default: name == "plugin",
                                            desc: "Skip JavaScript files"
 
         class_option :skip_turbolinks,     type: :boolean, default: false,
@@ -327,24 +324,17 @@ module Rails
       def assets_gemfile_entry
         return [] if options[:skip_sprockets]
 
-        gems = []
-        gems << GemfileEntry.version("sass-rails", "~> 5.0",
-                                     "Use SCSS for stylesheets")
-
-        if !options[:skip_javascript]
-          gems << GemfileEntry.version("uglifier",
-                                     ">= 1.3.0",
-                                     "Use Uglifier as compressor for JavaScript assets")
-        end
-
-        gems
+        GemfileEntry.version("sass-rails", "~> 5.0", "Use SCSS for stylesheets")
       end
 
       def webpacker_gemfile_entry
-        return [] unless options[:webpack]
+        return [] if options[:skip_javascript]
 
-        comment = "Transpile app-like JavaScript. Read more: https://github.com/rails/webpacker"
-        GemfileEntry.new "webpacker", nil, comment
+        if options.dev? || options.edge?
+          GemfileEntry.github "webpacker", "rails/webpacker", nil, "Use development version of Webpacker"
+        else
+          GemfileEntry.new "webpacker", nil, "Transpile app-like JavaScript. Read more: https://github.com/rails/webpacker"
+        end
       end
 
       def jbuilder_gemfile_entry
@@ -352,34 +342,12 @@ module Rails
         GemfileEntry.new "jbuilder", "~> 2.5", comment, {}, options[:api]
       end
 
-      def coffee_gemfile_entry
-        GemfileEntry.version "coffee-rails", "~> 4.2", "Use CoffeeScript for .coffee assets and views"
-      end
-
       def javascript_gemfile_entry
-        if options[:skip_javascript] || options[:skip_sprockets]
+        if options[:skip_javascript] || options[:skip_turbolinks]
           []
         else
-          gems = [javascript_runtime_gemfile_entry]
-          gems << coffee_gemfile_entry unless options[:skip_coffee]
-
-          unless options[:skip_turbolinks]
-            gems << GemfileEntry.version("turbolinks", "~> 5",
-             "Turbolinks makes navigating your web application faster. Read more: https://github.com/turbolinks/turbolinks")
-          end
-
-          gems
-        end
-      end
-
-      def javascript_runtime_gemfile_entry
-        comment = "See https://github.com/rails/execjs#readme for more supported runtimes"
-        if defined?(JRUBY_VERSION)
-          GemfileEntry.version "therubyrhino", nil, comment
-        elsif RUBY_PLATFORM.match?(/mingw|mswin/)
-          GemfileEntry.version "duktape", nil, comment
-        else
-          GemfileEntry.new "mini_racer", nil, comment, { platforms: :ruby }, true
+          [ GemfileEntry.version("turbolinks", "~> 5",
+             "Turbolinks makes navigating your web application faster. Read more: https://github.com/turbolinks/turbolinks") ]
         end
       end
 
@@ -452,9 +420,9 @@ module Rails
       end
 
       def run_webpack
-        if !(webpack = options[:webpack]).nil?
+        unless options[:skip_javascript]
           rails_command "webpacker:install"
-          rails_command "webpacker:install:#{webpack}" unless webpack == "webpack"
+          rails_command "webpacker:install:#{options[:webpack]}" if options[:webpack] && options[:webpack] != "webpack"
         end
       end
 
diff --git a/railties/lib/rails/generators/js/assets/assets_generator.rb b/railties/lib/rails/generators/js/assets/assets_generator.rb
deleted file mode 100644
index 9d32c666dc..0000000000
--- a/railties/lib/rails/generators/js/assets/assets_generator.rb
+++ /dev/null
@@ -1,15 +0,0 @@
-# frozen_string_literal: true
-
-require "rails/generators/named_base"
-
-module Js # :nodoc:
-  module Generators # :nodoc:
-    class AssetsGenerator < Rails::Generators::NamedBase # :nodoc:
-      source_root File.expand_path("templates", __dir__)
-
-      def copy_javascript
-        copy_file "javascript.js", File.join("app/assets/javascripts", class_path, "#{file_name}.js")
-      end
-    end
-  end
-end
diff --git a/railties/lib/rails/generators/js/assets/templates/javascript.js b/railties/lib/rails/generators/js/assets/templates/javascript.js
deleted file mode 100644
index dee720facd..0000000000
--- a/railties/lib/rails/generators/js/assets/templates/javascript.js
+++ /dev/null
@@ -1,2 +0,0 @@
-// Place all the behaviors and hooks related to the matching controller here.
-// All this logic will automatically be available in application.js.
diff --git a/railties/lib/rails/generators/rails/app/app_generator.rb b/railties/lib/rails/generators/rails/app/app_generator.rb
index a6d160f1eb..cefaffcb20 100644
--- a/railties/lib/rails/generators/rails/app/app_generator.rb
+++ b/railties/lib/rails/generators/rails/app/app_generator.rb
@@ -80,7 +80,6 @@ module Rails
       directory "app"
 
       keep_file "app/assets/images"
-      empty_directory_with_keep_file "app/assets/javascripts/channels" unless options[:skip_action_cable]
 
       keep_file  "app/controllers/concerns"
       keep_file  "app/models/concerns"
@@ -260,7 +259,7 @@ module Rails
                                  desc: "Don't run bundle install"
 
       class_option :webpack, type: :string, default: nil,
-                             desc: "Preconfigure for app-like JavaScript with Webpack (options: #{WEBPACKS.join('/')})"
+                             desc: "Preconfigure Webpack with a particular framework (options: #{WEBPACKS.join('/')})"
 
       def initialize(*args)
         super
@@ -409,7 +408,7 @@ module Rails
 
       def delete_js_folder_skipping_javascript
         if options[:skip_javascript]
-          remove_dir "app/assets/javascripts"
+          remove_dir "app/javascript"
         end
       end
 
@@ -436,7 +435,8 @@ module Rails
 
       def delete_action_cable_files_skipping_action_cable
         if options[:skip_action_cable]
-          remove_file "app/assets/javascripts/cable.js"
+          remove_file "app/javascript/channels/consumer.js"
+          remove_dir "app/javascript/channels"
           remove_dir "app/channels"
         end
       end
diff --git a/railties/lib/rails/generators/rails/app/templates/app/assets/config/manifest.js.tt b/railties/lib/rails/generators/rails/app/templates/app/assets/config/manifest.js.tt
index 70b579d10e..591819335f 100644
--- a/railties/lib/rails/generators/rails/app/templates/app/assets/config/manifest.js.tt
+++ b/railties/lib/rails/generators/rails/app/templates/app/assets/config/manifest.js.tt
@@ -1,5 +1,2 @@
 //= link_tree ../images
-<% unless options.skip_javascript -%>
-//= link_directory ../javascripts .js
-<% end -%>
 //= link_directory ../stylesheets .css
diff --git a/railties/lib/rails/generators/rails/app/templates/app/assets/javascripts/application.js.tt b/railties/lib/rails/generators/rails/app/templates/app/assets/javascripts/application.js.tt
deleted file mode 100644
index 5183bcd256..0000000000
--- a/railties/lib/rails/generators/rails/app/templates/app/assets/javascripts/application.js.tt
+++ /dev/null
@@ -1,22 +0,0 @@
-// This is a manifest file that'll be compiled into application.js, which will include all the files
-// listed below.
-//
-// Any JavaScript/Coffee file within this directory, lib/assets/javascripts, or any plugin's
-// vendor/assets/javascripts directory can be referenced here using a relative path.
-//
-// It's not advisable to add code directly here, but if you do, it'll appear at the bottom of the
-// compiled file. JavaScript code in this file should be added after the last require_* statement.
-//
-// Read Sprockets README (https://github.com/rails/sprockets#sprockets-directives) for details
-// about supported directives.
-//
-<% unless options[:skip_javascript] -%>
-//= require rails-ujs
-<% unless skip_active_storage? -%>
-//= require activestorage
-<% end -%>
-<% unless options[:skip_turbolinks] -%>
-//= require turbolinks
-<% end -%>
-<% end -%>
-//= require_tree .
diff --git a/railties/lib/rails/generators/rails/app/templates/app/assets/javascripts/cable.js.tt b/railties/lib/rails/generators/rails/app/templates/app/javascript/channels/consumer.js
index 739aa5f022..76ca3d0f2f 100644
--- a/railties/lib/rails/generators/rails/app/templates/app/assets/javascripts/cable.js.tt
+++ b/railties/lib/rails/generators/rails/app/templates/app/javascript/channels/consumer.js
@@ -1,13 +1,6 @@
 // Action Cable provides the framework to deal with WebSockets in Rails.
 // You can generate new channels where WebSocket features live using the `rails generate channel` command.
-//
-//= require action_cable
-//= require_self
-//= require_tree ./channels
 
-(function() {
-  this.App || (this.App = {});
+import ActionCable from "actioncable"
 
-  App.cable = ActionCable.createConsumer();
-
-}).call(this);
+export default ActionCable.createConsumer()
diff --git a/railties/lib/rails/generators/rails/app/templates/app/javascript/channels/index.js b/railties/lib/rails/generators/rails/app/templates/app/javascript/channels/index.js
new file mode 100644
index 0000000000..5da1ce2dce
--- /dev/null
+++ b/railties/lib/rails/generators/rails/app/templates/app/javascript/channels/index.js
@@ -0,0 +1,5 @@
+// Load all the channels within this directory and all subdirectories. 
+// Channel files must be named *_channel.js.
+
+const channels = require.context('.', true, /\_channel\.js$/)
+channels.keys().forEach(channels)
diff --git a/railties/lib/rails/generators/rails/app/templates/app/javascript/packs/application.js.tt b/railties/lib/rails/generators/rails/app/templates/app/javascript/packs/application.js.tt
new file mode 100644
index 0000000000..4d7a145cd6
--- /dev/null
+++ b/railties/lib/rails/generators/rails/app/templates/app/javascript/packs/application.js.tt
@@ -0,0 +1,21 @@
+// This file is automatically compiled by Webpack, along with any other files
+// present in this directory. You're encouraged to place your actual application logic in
+// a relevant structure within app/javascript and only use these pack files to reference
+// that code so it'll be compiled.
+
+import Rails from "rails-ujs"
+Rails.start()
+<%- unless options[:skip_turbolinks] -%>
+
+import Turbolinks from "turbolinks"
+Turbolinks.start()
+<%- end -%>
+<%- unless skip_active_storage? -%>
+
+import * as ActiveStorage from "activestorage"
+ActiveStorage.start()
+<%- end -%>
+<%- unless options[:skip_action_cable] -%>
+
+import "channels"
+<%- end -%>
diff --git a/railties/lib/rails/generators/rails/app/templates/app/views/layouts/application.html.erb.tt b/railties/lib/rails/generators/rails/app/templates/app/views/layouts/application.html.erb.tt
index ef715f1368..9a7267c783 100644
--- a/railties/lib/rails/generators/rails/app/templates/app/views/layouts/application.html.erb.tt
+++ b/railties/lib/rails/generators/rails/app/templates/app/views/layouts/application.html.erb.tt
@@ -9,11 +9,11 @@
     <%%= stylesheet_link_tag    'application', media: 'all' %>
     <%- else -%>
       <%- unless options[:skip_turbolinks] -%>
-    <%%= stylesheet_link_tag    'application', media: 'all', 'data-turbolinks-track': 'reload' %>
-    <%%= javascript_include_tag 'application', 'data-turbolinks-track': 'reload' %>
+    <%%= stylesheet_link_tag 'application', media: 'all', 'data-turbolinks-track': 'reload' %>
+    <%%= javascript_pack_tag 'application', 'data-turbolinks-track': 'reload' %>
       <%- else -%>
-    <%%= stylesheet_link_tag    'application', media: 'all' %>
-    <%%= javascript_include_tag 'application' %>
+    <%%= stylesheet_link_tag 'application', media: 'all' %>
+    <%%= javascript_pack_tag 'application' %>
       <%- end -%>
     <%- end -%>
   </head>
diff --git a/railties/lib/rails/generators/rails/app/templates/config/environments/production.rb.tt b/railties/lib/rails/generators/rails/app/templates/config/environments/production.rb.tt
index 888336af92..08befd9196 100644
--- a/railties/lib/rails/generators/rails/app/templates/config/environments/production.rb.tt
+++ b/railties/lib/rails/generators/rails/app/templates/config/environments/production.rb.tt
@@ -23,12 +23,7 @@ Rails.application.configure do
   config.public_file_server.enabled = ENV['RAILS_SERVE_STATIC_FILES'].present?
 
   <%- unless options.skip_sprockets? -%>
-  <%- if options.skip_javascript? -%>
-  # Compress CSS.
-  <%- else -%>
-  # Compress JavaScripts and CSS.
-  config.assets.js_compressor = :uglifier
-  <%- end -%>
+  # Compress CSS using a preprocessor.
   # config.assets.css_compressor = :sass
 
   # Do not fallback to assets pipeline if a precompiled asset is missed.
diff --git a/railties/lib/rails/generators/rails/app/templates/package.json.tt b/railties/lib/rails/generators/rails/app/templates/package.json.tt
index 46db57dcbe..a654cba39c 100644
--- a/railties/lib/rails/generators/rails/app/templates/package.json.tt
+++ b/railties/lib/rails/generators/rails/app/templates/package.json.tt
@@ -1,5 +1,11 @@
 {
   "name": "<%= app_name %>",
   "private": true,
-  "dependencies": {}
+  "dependencies": {
+    "rails-ujs": ">=5.2.1"<% unless options[:skip_turbolinks] %>,
+    "turbolinks": "5.1.1"<% end -%><% unless skip_active_storage? %>,
+    "activestorage": ">=5.2.1"<% end -%><% unless options[:skip_action_cable] %>,
+    "actioncable": ">=5.2.1"<% end -%>
+  },
+  "version": "0.1.0"
 }
diff --git a/railties/lib/rails/generators/rails/assets/USAGE b/railties/lib/rails/generators/rails/assets/USAGE
index d2e5ed4482..ee73d05808 100644
--- a/railties/lib/rails/generators/rails/assets/USAGE
+++ b/railties/lib/rails/generators/rails/assets/USAGE
@@ -5,16 +5,13 @@ Description:
     To create an asset within a folder, specify the asset's name as a
     path like 'parent/name'.
 
-    This generates a JavaScript stub in app/assets/javascripts and a stylesheet
-    stub in app/assets/stylesheets.
+    This generates a stylesheet stub in app/assets/stylesheets.
 
-    If CoffeeScript is available, JavaScripts will be generated with the .coffee extension.
     If Sass 3 is available, stylesheets will be generated with the .scss extension.
 
 Example:
     `rails generate assets posts`
 
     Posts assets.
-        JavaScript:     app/assets/javascripts/posts.js
         Stylesheet:     app/assets/stylesheets/posts.css
 
diff --git a/railties/lib/rails/generators/rails/assets/assets_generator.rb b/railties/lib/rails/generators/rails/assets/assets_generator.rb
index ffb695a1f3..9ce8570172 100644
--- a/railties/lib/rails/generators/rails/assets/assets_generator.rb
+++ b/railties/lib/rails/generators/rails/assets/assets_generator.rb
@@ -3,22 +3,14 @@
 module Rails
   module Generators
     class AssetsGenerator < NamedBase # :nodoc:
-      class_option :javascripts, type: :boolean, desc: "Generate JavaScripts"
       class_option :stylesheets, type: :boolean, desc: "Generate Stylesheets"
-
-      class_option :javascript_engine, desc: "Engine for JavaScripts"
       class_option :stylesheet_engine, desc: "Engine for Stylesheets"
 
       private
-
         def asset_name
           file_name
         end
 
-        hook_for :javascript_engine do |javascript_engine|
-          invoke javascript_engine, [name] if options[:javascripts]
-        end
-
         hook_for :stylesheet_engine do |stylesheet_engine|
           invoke stylesheet_engine, [name] if options[:stylesheets]
         end
diff --git a/railties/lib/rails/generators/rails/assets/templates/javascript.js b/railties/lib/rails/generators/rails/assets/templates/javascript.js
deleted file mode 100644
index dee720facd..0000000000
--- a/railties/lib/rails/generators/rails/assets/templates/javascript.js
+++ /dev/null
@@ -1,2 +0,0 @@
-// Place all the behaviors and hooks related to the matching controller here.
-// All this logic will automatically be available in application.js.
diff --git a/railties/lib/rails/generators/rails/plugin/plugin_generator.rb b/railties/lib/rails/generators/rails/plugin/plugin_generator.rb
index 8cc42325bb..9ec0ccbe7a 100644
--- a/railties/lib/rails/generators/rails/plugin/plugin_generator.rb
+++ b/railties/lib/rails/generators/rails/plugin/plugin_generator.rb
@@ -113,7 +113,7 @@ task default: :test
     end
 
     def test_dummy_assets
-      template "rails/javascripts.js",    "#{dummy_path}/app/assets/javascripts/application.js", force: true
+      template "rails/javascripts.js",    "#{dummy_path}/app/javascript/packs/application.js", force: true
       template "rails/stylesheets.css",   "#{dummy_path}/app/assets/stylesheets/application.css", force: true
       template "rails/dummy_manifest.js", "#{dummy_path}/app/assets/config/manifest.js", force: true
     end
diff --git a/railties/lib/rails/generators/testing/behaviour.rb b/railties/lib/rails/generators/testing/behaviour.rb
index 6ab88bd59f..238ffdd677 100644
--- a/railties/lib/rails/generators/testing/behaviour.rb
+++ b/railties/lib/rails/generators/testing/behaviour.rb
@@ -67,6 +67,9 @@ module Rails
         def run_generator(args = default_arguments, config = {})
           capture(:stdout) do
             args += ["--skip-bundle"] unless args.include? "--dev"
+            args |= ["--skip-bootsnap"] unless args.include? "--no-skip-bootsnap"
+            args |= ["--skip-javascript"] unless args.include? "--no-skip-javascript"
+
             generator_class.start(args, config.reverse_merge(destination_root: destination_root))
           end
         end
diff --git a/railties/lib/rails/tasks/statistics.rake b/railties/lib/rails/tasks/statistics.rake
index 594db91eec..8cacf4a49f 100644
--- a/railties/lib/rails/tasks/statistics.rake
+++ b/railties/lib/rails/tasks/statistics.rake
@@ -11,6 +11,7 @@ STATS_DIRECTORIES = [
   %w(Mailers            app/mailers),
   %w(Channels           app/channels),
   %w(JavaScripts        app/assets/javascripts),
+  %w(JavaScript         app/javascript),
   %w(Libraries          lib/),
   %w(APIs               app/apis),
   %w(Controller\ tests  test/controllers),
diff --git a/railties/test/application/assets_test.rb b/railties/test/application/assets_test.rb
index 4ca6d02b85..46ee0d670e 100644
--- a/railties/test/application/assets_test.rb
+++ b/railties/test/application/assets_test.rb
@@ -68,20 +68,6 @@ module ApplicationTests
       assert_equal 'a = "/assets/rails.png";', last_response.body.strip
     end
 
-    test "assets do not require compressors until it is used" do
-      app_file "app/assets/javascripts/demo.js.erb", "<%= :alert %>();"
-      add_to_env_config "production", "config.assets.compile = true"
-      add_to_env_config "production", "config.assets.precompile = []"
-
-      # Load app env
-      app "production"
-
-      assert_not defined?(Uglifier)
-      get "/assets/demo.js"
-      assert_match "alert()", last_response.body
-      assert defined?(Uglifier)
-    end
-
     test "precompile creates the file, gives it the original asset's content and run in production as default" do
       app_file "app/assets/config/manifest.js", "//= link_tree ../javascripts"
       app_file "app/assets/javascripts/application.js", "alert();"
@@ -443,13 +429,13 @@ module ApplicationTests
     end
 
     test "digested assets are not mistakenly removed" do
-      app_file "app/assets/application.js", "alert();"
+      app_file "app/assets/application.css", "div { font-weight: bold }"
       add_to_config "config.assets.compile = true"
 
       precompile!
 
-      files = Dir["#{app_path}/public/assets/application-*.js"]
-      assert_equal 1, files.length, "Expected digested application.js asset to be generated, but none found"
+      files = Dir["#{app_path}/public/assets/application-*.css"]
+      assert_equal 1, files.length, "Expected digested application.css asset to be generated, but none found"
     end
 
     test "digested assets are removed from configured path" do
diff --git a/railties/test/application/middleware_test.rb b/railties/test/application/middleware_test.rb
index 5efaf841d4..631f5bac7f 100644
--- a/railties/test/application/middleware_test.rb
+++ b/railties/test/application/middleware_test.rb
@@ -25,6 +25,7 @@ module ApplicationTests
       boot!
 
       assert_equal [
+        "Webpacker::DevServerProxy",
         "Rack::Sendfile",
         "ActionDispatch::Static",
         "ActionDispatch::Executor",
@@ -56,6 +57,7 @@ module ApplicationTests
       boot!
 
       assert_equal [
+        "Webpacker::DevServerProxy",
         "Rack::Sendfile",
         "ActionDispatch::Static",
         "ActionDispatch::Executor",
@@ -138,7 +140,7 @@ module ApplicationTests
       add_to_config "config.ssl_options = { redirect: { host: 'example.com' } }"
       boot!
 
-      assert_equal [{ redirect: { host: "example.com" } }], Rails.application.middleware.first.args
+      assert_equal [{ redirect: { host: "example.com" } }], Rails.application.middleware[1].args
     end
 
     test "removing Active Record omits its middleware" do
@@ -222,30 +224,31 @@ module ApplicationTests
     test "insert middleware after" do
       add_to_config "config.middleware.insert_after Rack::Sendfile, Rack::Config"
       boot!
-      assert_equal "Rack::Config", middleware.second
+      assert_equal "Rack::Config", middleware.third
     end
 
     test "unshift middleware" do
       add_to_config "config.middleware.unshift Rack::Config"
       boot!
-      assert_equal "Rack::Config", middleware.first
+      assert_equal "Rack::Config", middleware.second
     end
 
     test "Rails.cache does not respond to middleware" do
       add_to_config "config.cache_store = :memory_store"
       boot!
-      assert_equal "Rack::Runtime", middleware.fourth
+      assert_equal "Rack::Runtime", middleware.fifth
     end
 
     test "Rails.cache does respond to middleware" do
       boot!
-      assert_equal "Rack::Runtime", middleware.fifth
+      assert_equal "ActiveSupport::Cache::Strategy::LocalCache", middleware.fifth
+      assert_equal "Rack::Runtime", middleware[5]
     end
 
     test "insert middleware before" do
       add_to_config "config.middleware.insert_before Rack::Sendfile, Rack::Config"
       boot!
-      assert_equal "Rack::Config", middleware.first
+      assert_equal "Rack::Config", middleware.second
     end
 
     test "can't change middleware after it's built" do
diff --git a/railties/test/application/rake_test.rb b/railties/test/application/rake_test.rb
index 1522a2bbc5..a0cdae898b 100644
--- a/railties/test/application/rake_test.rb
+++ b/railties/test/application/rake_test.rb
@@ -118,7 +118,7 @@ module ApplicationTests
     end
 
     def test_code_statistics_sanity
-      assert_match "Code LOC: 25     Test LOC: 0     Code to Test Ratio: 1:0.0",
+      assert_match "Code LOC: 32     Test LOC: 0     Code to Test Ratio: 1:0.0",
         rails("stats")
     end
 
@@ -190,6 +190,7 @@ module ApplicationTests
       rails "generate", "model", "Cart"
       rails "generate", "scaffold", "LineItems", "product:references", "cart:belongs_to"
       with_rails_env("test") { rails("db:migrate") }
+      rails("webpacker:compile")
       output = rails("test")
 
       assert_match(/7 runs, 9 assertions, 0 failures, 0 errors/, output)
diff --git a/railties/test/engine/commands_test.rb b/railties/test/engine/commands_test.rb
index 48c93af80c..0e5167578d 100644
--- a/railties/test/engine/commands_test.rb
+++ b/railties/test/engine/commands_test.rb
@@ -24,7 +24,7 @@ class Rails::Engine::CommandsTest < ActiveSupport::TestCase
 
   def test_runner_command_work_inside_engine
     output = capture(:stdout) do
-      Dir.chdir(plugin_path) { system("bin/rails runner 'puts Rails.env'") }
+      Dir.chdir(plugin_path) { system({ "SKIP_REQUIRE_WEBPACKER" => "true" }, "bin/rails runner 'puts Rails.env'") }
     end
 
     assert_equal "test", output.strip
@@ -67,6 +67,7 @@ class Rails::Engine::CommandsTest < ActiveSupport::TestCase
 
     def spawn_command(command, fd)
       Process.spawn(
+        { "SKIP_REQUIRE_WEBPACKER" => "true" },
         "#{plugin_path}/bin/rails #{command}",
         in: fd, out: fd, err: fd
       )
diff --git a/railties/test/generators/api_app_generator_test.rb b/railties/test/generators/api_app_generator_test.rb
index c2540f4091..4f2894e71e 100644
--- a/railties/test/generators/api_app_generator_test.rb
+++ b/railties/test/generators/api_app_generator_test.rb
@@ -40,7 +40,6 @@ class ApiAppGeneratorTest < Rails::Generators::TestCase
     end
 
     assert_file "Gemfile" do |content|
-      assert_no_match(/gem 'coffee-rails'/, content)
       assert_no_match(/gem 'sass-rails'/, content)
       assert_no_match(/gem 'web-console'/, content)
       assert_no_match(/gem 'capybara'/, content)
diff --git a/railties/test/generators/app_generator_test.rb b/railties/test/generators/app_generator_test.rb
index 1169633244..48e8b7123f 100644
--- a/railties/test/generators/app_generator_test.rb
+++ b/railties/test/generators/app_generator_test.rb
@@ -13,10 +13,9 @@ DEFAULT_APP_FILES = %w(
   config.ru
   app/assets/config/manifest.js
   app/assets/images
-  app/assets/javascripts
-  app/assets/javascripts/application.js
-  app/assets/javascripts/cable.js
-  app/assets/javascripts/channels
+  app/javascript
+  app/javascript/channels
+  app/javascript/packs/application.js
   app/assets/stylesheets
   app/assets/stylesheets/application.css
   app/channels/application_cable/channel.rb
@@ -114,12 +113,12 @@ class AppGeneratorTest < Rails::Generators::TestCase
   end
 
   def test_assets
-    run_generator
+    run_generator [destination_root, "--no-skip-javascript"]
 
     assert_file("app/views/layouts/application.html.erb", /stylesheet_link_tag\s+'application', media: 'all', 'data-turbolinks-track': 'reload'/)
-    assert_file("app/views/layouts/application.html.erb", /javascript_include_tag\s+'application', 'data-turbolinks-track': 'reload'/)
+    assert_file("app/views/layouts/application.html.erb", /javascript_pack_tag\s+'application', 'data-turbolinks-track': 'reload'/)
     assert_file("app/assets/stylesheets/application.css")
-    assert_file("app/assets/javascripts/application.js")
+    assert_file("app/javascript/packs/application.js")
   end
 
   def test_application_job_file_present
@@ -215,7 +214,8 @@ class AppGeneratorTest < Rails::Generators::TestCase
 
   def test_new_application_load_defaults
     app_root = File.join(destination_root, "myfirstapp")
-    run_generator [app_root]
+    run_generator [app_root, "--no-skip-javascript"]
+
     output = nil
 
     assert_file "#{app_root}/config/application.rb", /\s+config\.load_defaults #{Rails::VERSION::STRING.to_f}/
@@ -559,7 +559,6 @@ class AppGeneratorTest < Rails::Generators::TestCase
     run_generator
 
     assert_gem "sass-rails"
-    assert_gem "uglifier"
   end
 
   def test_action_cable_redis_gems
@@ -601,24 +600,6 @@ class AppGeneratorTest < Rails::Generators::TestCase
     end
   end
 
-  def test_inclusion_of_javascript_runtime
-    run_generator
-    if defined?(JRUBY_VERSION)
-      assert_gem "therubyrhino"
-    elsif RUBY_PLATFORM =~ /mingw|mswin/
-      assert_gem "duktape"
-    else
-      assert_file "Gemfile", /# gem 'mini_racer', platforms: :ruby/
-    end
-  end
-
-  def test_rails_ujs_is_the_default_ujs_library
-    run_generator
-    assert_file "app/assets/javascripts/application.js" do |contents|
-      assert_match %r{^//= require rails-ujs}, contents
-    end
-  end
-
   def test_javascript_is_skipped_if_required
     run_generator [destination_root, "--skip-javascript"]
 
@@ -628,22 +609,6 @@ class AppGeneratorTest < Rails::Generators::TestCase
       assert_match(/stylesheet_link_tag\s+'application', media: 'all' %>/, contents)
       assert_no_match(/javascript_include_tag\s+'application' \%>/, contents)
     end
-
-    assert_no_gem "coffee-rails"
-    assert_no_gem "uglifier"
-
-    assert_file "config/environments/production.rb" do |content|
-      assert_no_match(/config\.assets\.js_compressor = :uglifier/, content)
-    end
-  end
-
-  def test_coffeescript_is_skipped_if_required
-    run_generator [destination_root, "--skip-coffee"]
-
-    assert_file "Gemfile" do |content|
-      assert_no_match(/coffee-rails/, content)
-      assert_match(/uglifier/, content)
-    end
   end
 
   def test_inclusion_of_jbuilder
@@ -819,22 +784,22 @@ class AppGeneratorTest < Rails::Generators::TestCase
     assert_no_gem "spring"
   end
 
-  def test_webpack_option
+  def test_skip_javascript_option
     command_check = -> command, *_ do
       @called ||= 0
       if command == "webpacker:install"
         @called += 1
-        assert_equal 1, @called, "webpacker:install expected to be called once, but was called #{@called} times."
+        assert_equal 0, @called, "webpacker:install expected not to be called once, but was called #{@called} times."
       end
     end
 
-    generator([destination_root], webpack: "webpack").stub(:rails_command, command_check) do
+    generator([destination_root], skip_javascript: true).stub(:rails_command, command_check) do
       generator.stub :bundle_command, nil do
         quietly { generator.invoke_all }
       end
     end
 
-    assert_gem "webpacker"
+    assert_no_gem "webpacker"
   end
 
   def test_webpack_option_with_js_framework
@@ -856,22 +821,24 @@ class AppGeneratorTest < Rails::Generators::TestCase
         quietly { generator.invoke_all }
       end
     end
+
+    assert_gem "webpacker"
   end
 
   def test_generator_if_skip_turbolinks_is_given
-    run_generator [destination_root, "--skip-turbolinks"]
+    run_generator [destination_root, "--skip-turbolinks", "--no-skip-javascript"]
 
     assert_no_gem "turbolinks"
     assert_file "app/views/layouts/application.html.erb" do |content|
       assert_no_match(/data-turbolinks-track/, content)
     end
-    assert_file "app/assets/javascripts/application.js" do |content|
+    assert_file "app/javascript/packs/application.js" do |content|
       assert_no_match(/turbolinks/, content)
     end
   end
 
   def test_bootsnap
-    run_generator
+    run_generator [destination_root, "--no-skip-bootsnap"]
 
     unless defined?(JRUBY_VERSION)
       assert_gem "bootsnap"
@@ -972,7 +939,7 @@ class AppGeneratorTest < Rails::Generators::TestCase
       template
     end
 
-    sequence = ["git init", "install", "binstubs bundler", "exec spring binstub --all", "echo ran after_bundle"]
+    sequence = ["git init", "install", "binstubs bundler", "exec spring binstub --all", "webpacker:install", "echo ran after_bundle"]
     @sequence_step ||= 0
     ensure_bundler_first = -> command, options = nil do
       assert_equal sequence[@sequence_step], command, "commands should be called in sequence #{sequence}"
@@ -989,7 +956,7 @@ class AppGeneratorTest < Rails::Generators::TestCase
       end
     end
 
-    assert_equal 5, @sequence_step
+    assert_equal 6, @sequence_step
   end
 
   def test_gitignore
diff --git a/railties/test/generators/assets_generator_test.rb b/railties/test/generators/assets_generator_test.rb
index 3cec41dbf8..83d2429acf 100644
--- a/railties/test/generators/assets_generator_test.rb
+++ b/railties/test/generators/assets_generator_test.rb
@@ -9,13 +9,11 @@ class AssetsGeneratorTest < Rails::Generators::TestCase
 
   def test_assets
     run_generator
-    assert_file "app/assets/javascripts/posts.js"
     assert_file "app/assets/stylesheets/posts.css"
   end
 
   def test_skipping_assets
-    run_generator ["posts", "--no-stylesheets", "--no-javascripts"]
-    assert_no_file "app/assets/javascripts/posts.js"
+    run_generator ["posts", "--no-stylesheets"]
     assert_no_file "app/assets/stylesheets/posts.css"
   end
 end
diff --git a/railties/test/generators/channel_generator_test.rb b/railties/test/generators/channel_generator_test.rb
index e543cc11b8..265d7c9618 100644
--- a/railties/test/generators/channel_generator_test.rb
+++ b/railties/test/generators/channel_generator_test.rb
@@ -26,8 +26,8 @@ class ChannelGeneratorTest < Rails::Generators::TestCase
       assert_match(/class ChatChannel < ApplicationCable::Channel/, channel)
     end
 
-    assert_file "app/assets/javascripts/channels/chat.js" do |channel|
-      assert_match(/App\.chat = App\.cable\.subscriptions\.create\("ChatChannel/, channel)
+    assert_file "app/javascript/channels/chat_channel.js" do |channel|
+      assert_match(/import consumer from "\.\/consumer"\s+consumer\.subscriptions\.create\("ChatChannel/, channel)
     end
   end
 
@@ -40,8 +40,8 @@ class ChannelGeneratorTest < Rails::Generators::TestCase
       assert_match(/def mute/, channel)
     end
 
-    assert_file "app/assets/javascripts/channels/chat.js" do |channel|
-      assert_match(/App\.chat = App\.cable\.subscriptions\.create\("ChatChannel/, channel)
+    assert_file "app/javascript/channels/chat_channel.js" do |channel|
+      assert_match(/import consumer from "\.\/consumer"\s+consumer\.subscriptions\.create\("ChatChannel/, channel)
       assert_match(/,\n\n  speak/, channel)
       assert_match(/,\n\n  mute: function\(\) \{\n    return this\.perform\('mute'\);\n  \}\n\}\);/, channel)
     end
@@ -54,15 +54,17 @@ class ChannelGeneratorTest < Rails::Generators::TestCase
       assert_match(/class ChatChannel < ApplicationCable::Channel/, channel)
     end
 
-    assert_no_file "app/assets/javascripts/channels/chat.js"
+    assert_no_file "app/javascript/channels/chat_channel.js"
   end
 
   def test_cable_js_is_created_if_not_present_already
     run_generator ["chat"]
-    FileUtils.rm("#{destination_root}/app/assets/javascripts/cable.js")
+    FileUtils.rm("#{destination_root}/app/javascript/channels/index.js")
+    FileUtils.rm("#{destination_root}/app/javascript/channels/consumer.js")
     run_generator ["camp"]
 
-    assert_file "app/assets/javascripts/cable.js"
+    assert_file "app/javascript/channels/index.js"
+    assert_file "app/javascript/channels/consumer.js"
   end
 
   def test_channel_on_revoke
@@ -74,7 +76,8 @@ class ChannelGeneratorTest < Rails::Generators::TestCase
 
     assert_file "app/channels/application_cable/channel.rb"
     assert_file "app/channels/application_cable/connection.rb"
-    assert_file "app/assets/javascripts/cable.js"
+    assert_file "app/javascript/channels/index.js"
+    assert_file "app/javascript/channels/consumer.js"
   end
 
   def test_channel_suffix_is_not_duplicated
@@ -84,6 +87,6 @@ class ChannelGeneratorTest < Rails::Generators::TestCase
     assert_file "app/channels/chat_channel.rb"
 
     assert_no_file "app/assets/javascripts/channels/chat_channel.js"
-    assert_file "app/assets/javascripts/channels/chat.js"
+    assert_file "app/javascript/channels/chat_channel.js"
   end
 end
diff --git a/railties/test/generators/controller_generator_test.rb b/railties/test/generators/controller_generator_test.rb
index 021004c9b8..adef56255a 100644
--- a/railties/test/generators/controller_generator_test.rb
+++ b/railties/test/generators/controller_generator_test.rb
@@ -39,13 +39,11 @@ class ControllerGeneratorTest < Rails::Generators::TestCase
 
   def test_invokes_assets
     run_generator
-    assert_file "app/assets/javascripts/account.js"
     assert_file "app/assets/stylesheets/account.css"
   end
 
   def test_does_not_invoke_assets_if_required
     run_generator ["account", "--skip-assets"]
-    assert_no_file "app/assets/javascripts/account.js"
     assert_no_file "app/assets/stylesheets/account.css"
   end
 
@@ -133,7 +131,6 @@ class ControllerGeneratorTest < Rails::Generators::TestCase
     assert_file "app/helpers/account_helper.rb"
 
     assert_no_file "app/assets/javascripts/account_controller.js"
-    assert_file "app/assets/javascripts/account.js"
 
     assert_no_file "app/assets/stylesheets/account_controller.css"
     assert_file "app/assets/stylesheets/account.css"
diff --git a/railties/test/generators/plugin_generator_test.rb b/railties/test/generators/plugin_generator_test.rb
index 468a9c9e89..66286fc554 100644
--- a/railties/test/generators/plugin_generator_test.rb
+++ b/railties/test/generators/plugin_generator_test.rb
@@ -140,10 +140,6 @@ class PluginGeneratorTest < Rails::Generators::TestCase
     run_generator
 
     assert_file "test/dummy/app/assets/stylesheets/application.css"
-
-    assert_file "test/dummy/app/assets/javascripts/application.js" do |contents|
-      assert_no_match(/jquery/, contents)
-    end
   end
 
   def test_ensure_that_plugin_options_are_not_passed_to_app_generator
@@ -210,28 +206,10 @@ class PluginGeneratorTest < Rails::Generators::TestCase
     assert_no_file "#{destination_root}/Gemfile.lock"
   end
 
-  def test_skipping_javascripts_without_mountable_option
-    run_generator
-    assert_no_file "app/assets/javascripts/bukkits/application.js"
-  end
-
-  def test_javascripts_generation
-    run_generator [destination_root, "--mountable"]
-    assert_file "app/assets/javascripts/bukkits/application.js" do |content|
-      assert_match "//= require rails-ujs", content
-      assert_match "//= require activestorage", content
-      assert_match "//= require_tree .", content
-    end
-    assert_file "app/views/layouts/bukkits/application.html.erb" do |content|
-      assert_match "javascript_include_tag", content
-    end
-  end
-
-  def test_skip_javascripts
+  def test_skip_javascript
     run_generator [destination_root, "--skip-javascript", "--mountable"]
-    assert_no_file "app/assets/javascripts/bukkits/application.js"
     assert_file "app/views/layouts/bukkits/application.html.erb" do |content|
-      assert_no_match "javascript_include_tag", content
+      assert_no_match "javascript_pack_tag", content
     end
   end
 
@@ -264,7 +242,6 @@ class PluginGeneratorTest < Rails::Generators::TestCase
 
   def test_creating_engine_in_full_mode
     run_generator [destination_root, "--full"]
-    assert_file "app/assets/javascripts/bukkits"
     assert_file "app/assets/stylesheets/bukkits"
     assert_file "app/assets/images/bukkits"
     assert_file "app/models"
@@ -280,7 +257,7 @@ class PluginGeneratorTest < Rails::Generators::TestCase
 
   def test_creating_engine_with_hyphenated_name_in_full_mode
     run_generator [File.join(destination_root, "hyphenated-name"), "--full"]
-    assert_file "hyphenated-name/app/assets/javascripts/hyphenated/name"
+    assert_no_file "hyphenated-name/app/assets/javascripts/hyphenated/name"
     assert_file "hyphenated-name/app/assets/stylesheets/hyphenated/name"
     assert_file "hyphenated-name/app/assets/images/hyphenated/name"
     assert_file "hyphenated-name/app/models"
@@ -297,7 +274,7 @@ class PluginGeneratorTest < Rails::Generators::TestCase
 
   def test_creating_engine_with_hyphenated_and_underscored_name_in_full_mode
     run_generator [File.join(destination_root, "my_hyphenated-name"), "--full"]
-    assert_file "my_hyphenated-name/app/assets/javascripts/my_hyphenated/name"
+    assert_no_file "my_hyphenated-name/app/assets/javascripts/my_hyphenated/name"
     assert_file "my_hyphenated-name/app/assets/stylesheets/my_hyphenated/name"
     assert_file "my_hyphenated-name/app/assets/images/my_hyphenated/name"
     assert_file "my_hyphenated-name/app/models"
@@ -318,7 +295,7 @@ class PluginGeneratorTest < Rails::Generators::TestCase
 
   def test_create_mountable_application_with_mountable_option
     run_generator [destination_root, "--mountable"]
-    assert_file "app/assets/javascripts/bukkits"
+    assert_no_file "app/assets/javascripts/bukkits"
     assert_file "app/assets/stylesheets/bukkits"
     assert_file "app/assets/images/bukkits"
     assert_file "config/routes.rb", /Bukkits::Engine\.routes\.draw do/
@@ -334,7 +311,7 @@ class PluginGeneratorTest < Rails::Generators::TestCase
       assert_match "<%= csrf_meta_tags %>", contents
       assert_match "<%= csp_meta_tag %>", contents
       assert_match(/stylesheet_link_tag\s+['"]bukkits\/application['"]/, contents)
-      assert_match(/javascript_include_tag\s+['"]bukkits\/application['"]/, contents)
+      assert_no_match(/javascript_include_tag\s+['"]bukkits\/application['"]/, contents)
       assert_match "<%= yield %>", contents
     end
     assert_file "test/test_helper.rb" do |content|
@@ -348,7 +325,7 @@ class PluginGeneratorTest < Rails::Generators::TestCase
 
   def test_create_mountable_application_with_mountable_option_and_hypenated_name
     run_generator [File.join(destination_root, "hyphenated-name"), "--mountable"]
-    assert_file "hyphenated-name/app/assets/javascripts/hyphenated/name"
+    assert_no_file "hyphenated-name/app/assets/javascripts/hyphenated/name"
     assert_file "hyphenated-name/app/assets/stylesheets/hyphenated/name"
     assert_file "hyphenated-name/app/assets/images/hyphenated/name"
     assert_file "hyphenated-name/config/routes.rb",                                          /Hyphenated::Name::Engine\.routes\.draw do/
@@ -364,13 +341,13 @@ class PluginGeneratorTest < Rails::Generators::TestCase
     assert_file "hyphenated-name/app/views/layouts/hyphenated/name/application.html.erb" do |contents|
       assert_match "<title>Hyphenated name</title>", contents
       assert_match(/stylesheet_link_tag\s+['"]hyphenated\/name\/application['"]/, contents)
-      assert_match(/javascript_include_tag\s+['"]hyphenated\/name\/application['"]/, contents)
+      assert_no_match(/javascript_include_tag\s+['"]hyphenated\/name\/application['"]/, contents)
     end
   end
 
   def test_create_mountable_application_with_mountable_option_and_hypenated_and_underscored_name
     run_generator [File.join(destination_root, "my_hyphenated-name"), "--mountable"]
-    assert_file "my_hyphenated-name/app/assets/javascripts/my_hyphenated/name"
+    assert_no_file "my_hyphenated-name/app/assets/javascripts/my_hyphenated/name"
     assert_file "my_hyphenated-name/app/assets/stylesheets/my_hyphenated/name"
     assert_file "my_hyphenated-name/app/assets/images/my_hyphenated/name"
     assert_file "my_hyphenated-name/config/routes.rb",                                             /MyHyphenated::Name::Engine\.routes\.draw do/
@@ -386,13 +363,13 @@ class PluginGeneratorTest < Rails::Generators::TestCase
     assert_file "my_hyphenated-name/app/views/layouts/my_hyphenated/name/application.html.erb" do |contents|
       assert_match "<title>My hyphenated name</title>", contents
       assert_match(/stylesheet_link_tag\s+['"]my_hyphenated\/name\/application['"]/, contents)
-      assert_match(/javascript_include_tag\s+['"]my_hyphenated\/name\/application['"]/, contents)
+      assert_no_match(/javascript_include_tag\s+['"]my_hyphenated\/name\/application['"]/, contents)
     end
   end
 
   def test_create_mountable_application_with_mountable_option_and_multiple_hypenates_in_name
     run_generator [File.join(destination_root, "deep-hyphenated-name"), "--mountable"]
-    assert_file "deep-hyphenated-name/app/assets/javascripts/deep/hyphenated/name"
+    assert_no_file "deep-hyphenated-name/app/assets/javascripts/deep/hyphenated/name"
     assert_file "deep-hyphenated-name/app/assets/stylesheets/deep/hyphenated/name"
     assert_file "deep-hyphenated-name/app/assets/images/deep/hyphenated/name"
     assert_file "deep-hyphenated-name/config/routes.rb",                                               /Deep::Hyphenated::Name::Engine\.routes\.draw do/
@@ -408,7 +385,7 @@ class PluginGeneratorTest < Rails::Generators::TestCase
     assert_file "deep-hyphenated-name/app/views/layouts/deep/hyphenated/name/application.html.erb" do |contents|
       assert_match "<title>Deep hyphenated name</title>", contents
       assert_match(/stylesheet_link_tag\s+['"]deep\/hyphenated\/name\/application['"]/, contents)
-      assert_match(/javascript_include_tag\s+['"]deep\/hyphenated\/name\/application['"]/, contents)
+      assert_no_match(/javascript_include_tag\s+['"]deep\/hyphenated\/name\/application['"]/, contents)
     end
   end
 
diff --git a/railties/test/generators/scaffold_generator_test.rb b/railties/test/generators/scaffold_generator_test.rb
index 94aab15aa9..21b5013484 100644
--- a/railties/test/generators/scaffold_generator_test.rb
+++ b/railties/test/generators/scaffold_generator_test.rb
@@ -93,7 +93,6 @@ class ScaffoldGeneratorTest < Rails::Generators::TestCase
 
     # Assets
     assert_file "app/assets/stylesheets/scaffold.css"
-    assert_file "app/assets/javascripts/product_lines.js"
     assert_file "app/assets/stylesheets/product_lines.css"
   end
 
@@ -166,7 +165,6 @@ class ScaffoldGeneratorTest < Rails::Generators::TestCase
 
     # Assets
     assert_no_file "app/assets/stylesheets/scaffold.css"
-    assert_no_file "app/assets/javascripts/product_lines.js"
     assert_no_file "app/assets/stylesheets/product_lines.css"
   end
 
@@ -222,7 +220,6 @@ class ScaffoldGeneratorTest < Rails::Generators::TestCase
 
     # Assets
     assert_file "app/assets/stylesheets/scaffold.css", /:visited/
-    assert_no_file "app/assets/javascripts/product_lines.js"
     assert_no_file "app/assets/stylesheets/product_lines.css"
   end
 
@@ -299,7 +296,6 @@ class ScaffoldGeneratorTest < Rails::Generators::TestCase
 
     # Assets
     assert_file "app/assets/stylesheets/scaffold.css", /:visited/
-    assert_file "app/assets/javascripts/admin/roles.js"
     assert_file "app/assets/stylesheets/admin/roles.css"
   end
 
@@ -335,7 +331,6 @@ class ScaffoldGeneratorTest < Rails::Generators::TestCase
 
     # Assets
     assert_file "app/assets/stylesheets/scaffold.css"
-    assert_no_file "app/assets/javascripts/admin/roles.js"
     assert_no_file "app/assets/stylesheets/admin/roles.css"
   end
 
@@ -380,28 +375,24 @@ class ScaffoldGeneratorTest < Rails::Generators::TestCase
   def test_scaffold_generator_no_assets_with_switch_no_assets
     run_generator [ "posts", "--no-assets" ]
     assert_no_file "app/assets/stylesheets/scaffold.css"
-    assert_no_file "app/assets/javascripts/posts.js"
     assert_no_file "app/assets/stylesheets/posts.css"
   end
 
   def test_scaffold_generator_no_assets_with_switch_assets_false
     run_generator [ "posts", "--assets=false" ]
     assert_no_file "app/assets/stylesheets/scaffold.css"
-    assert_no_file "app/assets/javascripts/posts.js"
     assert_no_file "app/assets/stylesheets/posts.css"
   end
 
   def test_scaffold_generator_no_scaffold_stylesheet_with_switch_no_scaffold_stylesheet
     run_generator [ "posts", "--no-scaffold-stylesheet" ]
     assert_no_file "app/assets/stylesheets/scaffold.css"
-    assert_file "app/assets/javascripts/posts.js"
     assert_file "app/assets/stylesheets/posts.css"
   end
 
   def test_scaffold_generator_no_scaffold_stylesheet_with_switch_scaffold_stylesheet_false
     run_generator [ "posts", "--scaffold-stylesheet=false" ]
     assert_no_file "app/assets/stylesheets/scaffold.css"
-    assert_file "app/assets/javascripts/posts.js"
     assert_file "app/assets/stylesheets/posts.css"
   end
 
@@ -429,17 +420,9 @@ class ScaffoldGeneratorTest < Rails::Generators::TestCase
   def test_scaffold_generator_no_stylesheets
     run_generator [ "posts", "--no-stylesheets" ]
     assert_no_file "app/assets/stylesheets/scaffold.css"
-    assert_file "app/assets/javascripts/posts.js"
     assert_no_file "app/assets/stylesheets/posts.css"
   end
 
-  def test_scaffold_generator_no_javascripts
-    run_generator [ "posts", "--no-javascripts" ]
-    assert_file "app/assets/stylesheets/scaffold.css"
-    assert_no_file "app/assets/javascripts/posts.js"
-    assert_file "app/assets/stylesheets/posts.css"
-  end
-
   def test_scaffold_generator_outputs_error_message_on_missing_attribute_type
     run_generator ["post", "title", "body:text", "author"]
 
@@ -630,7 +613,6 @@ class ScaffoldGeneratorTest < Rails::Generators::TestCase
 
       assert File.exist?("app/helpers/bukkits/users_helper.rb")
 
-      assert File.exist?("app/assets/javascripts/bukkits/users.js")
       assert File.exist?("app/assets/stylesheets/bukkits/users.css")
     end
   end
@@ -660,7 +642,6 @@ class ScaffoldGeneratorTest < Rails::Generators::TestCase
 
       assert_not File.exist?("app/helpers/bukkits/users_helper.rb")
 
-      assert_not File.exist?("app/assets/javascripts/bukkits/users.js")
       assert_not File.exist?("app/assets/stylesheets/bukkits/users.css")
     end
   end
diff --git a/railties/test/generators/shared_generator_tests.rb b/railties/test/generators/shared_generator_tests.rb
index 5a1257e5c1..521f775553 100644
--- a/railties/test/generators/shared_generator_tests.rb
+++ b/railties/test/generators/shared_generator_tests.rb
@@ -27,7 +27,7 @@ module SharedGeneratorTests
   end
 
   def test_skeleton_is_created
-    run_generator
+    run_generator [destination_root, "--no-skip-javascript"]
 
     default_files.each { |path| assert_file path }
   end
@@ -196,10 +196,12 @@ module SharedGeneratorTests
   end
 
   def test_generator_for_active_storage
-    run_generator
+    run_generator [destination_root, "--no-skip-javascript"]
 
-    assert_file "#{application_path}/app/assets/javascripts/application.js" do |content|
-      assert_match(/^\/\/= require activestorage/, content)
+    unless generator_class.name == "Rails::Generators::PluginGenerator"
+      assert_file "#{application_path}/app/javascript/packs/application.js" do |content|
+        assert_match(/^import \* as ActiveStorage from "activestorage"\nActiveStorage.start\(\)/, content)
+      end
     end
 
     assert_file "#{application_path}/config/environments/development.rb" do |content|
@@ -224,11 +226,11 @@ module SharedGeneratorTests
   end
 
   def test_generator_if_skip_active_storage_is_given
-    run_generator [destination_root, "--skip-active-storage"]
+    run_generator [destination_root, "--skip-active-storage", "--no-skip-javascript"]
 
     assert_file "#{application_path}/config/application.rb", /#\s+require\s+["']active_storage\/engine["']/
 
-    assert_file "#{application_path}/app/assets/javascripts/application.js" do |content|
+    assert_file "#{application_path}/app/javascript/packs/application.js" do |content|
       assert_no_match(/^\/\/= require activestorage/, content)
     end
 
@@ -254,12 +256,12 @@ module SharedGeneratorTests
   end
 
   def test_generator_does_not_generate_active_storage_contents_if_skip_active_record_is_given
-    run_generator [destination_root, "--skip-active-record"]
+    run_generator [destination_root, "--skip-active-record", "--no-skip-javascript"]
 
     assert_file "#{application_path}/config/application.rb", /#\s+require\s+["']active_storage\/engine["']/
 
-    assert_file "#{application_path}/app/assets/javascripts/application.js" do |content|
-      assert_no_match(/^\/\/= require activestorage/, content)
+    assert_file "#{application_path}/app/javascript/packs/application.js" do |content|
+      assert_no_match(/^import * as ActiveStorage from "activestorage"\nActiveStorage.start()/, content)
     end
 
     assert_file "#{application_path}/config/environments/development.rb" do |content|
@@ -320,8 +322,6 @@ module SharedGeneratorTests
 
     assert_file "Gemfile" do |content|
       assert_no_match(/sass-rails/, content)
-      assert_no_match(/uglifier/, content)
-      assert_no_match(/coffee-rails/, content)
     end
 
     assert_file "#{application_path}/config/environments/development.rb" do |content|
@@ -330,7 +330,6 @@ module SharedGeneratorTests
 
     assert_file "#{application_path}/config/environments/production.rb" do |content|
       assert_no_match(/config\.assets\.digest/, content)
-      assert_no_match(/config\.assets\.js_compressor/, content)
       assert_no_match(/config\.assets\.css_compressor/, content)
       assert_no_match(/config\.assets\.compile/, content)
     end
diff --git a/railties/test/isolation/abstract_unit.rb b/railties/test/isolation/abstract_unit.rb
index 2a8c6d8f97..e44f21380e 100644
--- a/railties/test/isolation/abstract_unit.rb
+++ b/railties/test/isolation/abstract_unit.rb
@@ -30,11 +30,11 @@ require "rails/secrets"
 module TestHelpers
   module Paths
     def app_template_path
-      File.join Dir.tmpdir, "app_template"
+      File.join RAILS_FRAMEWORK_ROOT, "tmp/templates/app_template"
     end
 
     def tmp_path(*args)
-      @tmp_path ||= File.realpath(Dir.mktmpdir)
+      @tmp_path ||= File.realpath(Dir.mktmpdir(nil, File.join(RAILS_FRAMEWORK_ROOT, "tmp")))
       File.join(@tmp_path, *args)
     end
 
@@ -469,17 +469,28 @@ Module.new do
 
   # Build a rails app
   FileUtils.rm_rf(app_template_path)
-  FileUtils.mkdir(app_template_path)
+  FileUtils.mkdir_p(app_template_path)
+
+  Dir.chdir "#{RAILS_FRAMEWORK_ROOT}/actionview" do
+    `yarn build`
+  end
 
   `#{Gem.ruby} #{RAILS_FRAMEWORK_ROOT}/railties/exe/rails new #{app_template_path} --skip-gemfile --skip-listen --no-rc`
   File.open("#{app_template_path}/config/boot.rb", "w") do |f|
     f.puts "require 'rails/all'"
   end
 
+  Dir.chdir(app_template_path) { `yarn add https://github.com/rails/webpacker.git` } # Use the latest version.
+
+  # Manually install `webpack` as bin symlinks are not created for subdependencies
+  # in workspaces. See https://github.com/yarnpkg/yarn/issues/4964
+  Dir.chdir(app_template_path) { `yarn add webpack@4.17.1 --tilde` }
+  Dir.chdir(app_template_path) { `yarn add webpack-cli` }
+
   # Fake 'Bundler.require' -- we run using the repo's Gemfile, not an
   # app-specific one: we don't want to require every gem that lists.
   contents = File.read("#{app_template_path}/config/application.rb")
-  contents.sub!(/^Bundler\.require.*/, "%w(turbolinks).each { |r| require r }")
+  contents.sub!(/^Bundler\.require.*/, "%w(turbolinks webpacker).each { |r| require r }")
   File.write("#{app_template_path}/config/application.rb", contents)
 
   require "rails"