Bootstrapのテンプレートを使用し、herokuにデプロイした時のエラーを解消したい。

前提・実現したいこと

Ruby言語を使用し、Railsでtoolサイトを作っています。
Bootstrapのテンプレートをviewファイルに入れた後、Herokuにデプロイしたいのですが、
下記のエラーが発生しました。
ローカル環境ではエラー無く動いております。

発生している問題・エラーメッセージ

console
1(略)
2remote:        Compiling...
3remote:        Compilation failed:
4remote:        ModuleNotFoundError: Module not found: Error: Can't resolve 'popper' in '/tmp/build_d812499c/app/javascript/packs'
5（略）
6remote:        resolve 'popper' in '/tmp/build_d812499c/app/javascript/packs'
7remote:          Parsed request is a module
8remote:          using description file: /tmp/build_d812499c/package.json (relative path: ./app/javascript/packs)
9remote:            Field 'browser' doesn't contain a valid alias configuration
10remote:            resolve as module
11remote:              looking for modules in /tmp/build_d812499c/app/javascript
12remote:                using description file: /tmp/build_d812499c/package.json (relative path: ./app/javascript)
13remote:                  Field 'browser' doesn't contain a valid alias configuration
14remote:                  using description file: /tmp/build_d812499c/package.json (relative path: ./app/javascript/popper)
15remote:                    no extension
16remote:                      Field 'browser' doesn't contain a valid alias configuration
17remote:                      /tmp/build_d812499c/app/javascript/popper doesn't exist
18（略）
19remote:  !
20remote:  !     Precompiling assets failed.
21remote:  !

該当のソースコード

Gemfile
1source 'https://rubygems.org'
2git_source(:github) { |repo| "https://github.com/#{repo}.git" }
3
4ruby '2.6.5'
5
6# Bundle edge Rails instead: gem 'rails', github: 'rails/rails'
7gem 'rails', '~> 6.0.0'
8# Use mysql as the database for Active Record
9gem 'mysql2', '>= 0.5.3'
10# Use Puma as the app server
11gem 'puma', '~> 3.11'
12# Use SCSS for stylesheets
13gem 'sass-rails', '~> 5'
14# Transpile app-like JavaScript. Read more: https://github.com/rails/webpacker
15gem 'webpacker', '~> 4.0'
16# Turbolinks makes navigating your web application faster. Read more: https://github.com/turbolinks/turbolinks
17gem 'turbolinks', '~> 5'
18# Build JSON APIs with ease. Read more: https://github.com/rails/jbuilder
19gem 'jbuilder', '~> 2.7'
20# Use Redis adapter to run Action Cable in production
21# gem 'redis', '~> 4.0'
22# Use Active Model has_secure_password
23# gem 'bcrypt', '~> 3.1.7'
24
25# Use Active Storage variant
26# gem 'image_processing', '~> 1.2'
27
28# Reduces boot times through caching; required in config/boot.rb
29gem 'bootsnap', '>= 1.4.2', require: false
30
31group :development, :test do
32  # Call 'byebug' anywhere in the code to stop execution and get a debugger console
33  gem 'byebug', platforms: [:mri, :mingw, :x64_mingw]
34
35  gem 'pry-rails'
36  gem 'rspec-rails', '~> 4.0.0'
37  gem 'factory_bot_rails'
38end
39
40group :development do
41  # Access an interactive console on exception pages or by calling 'console' anywhere in the code.
42  gem 'web-console', '>= 3.3.0'
43  gem 'listen', '>= 3.0.5', '< 3.2'
44  # Spring speeds up development by keeping your application running in the background. Read more: https://github.com/rails/spring
45  gem 'spring'
46  gem 'spring-watcher-listen', '~> 2.0.0'
47end
48
49group :test do
50  # Adds support for Capybara system testing and selenium driver
51  gem 'capybara', '>= 2.15'
52  gem 'selenium-webdriver'
53  # Easy installation and use of web drivers to run system tests with browsers
54  gem 'webdrivers'
55end
56
57# Windows does not include zoneinfo files, so bundle the tzinfo-data gem
58gem 'tzinfo-data', platforms: [:mingw, :mswin, :x64_mingw, :jruby]
59
60gem 'bootstrap', '~> 4.3.1'
61gem 'jquery-rails'
62
63gem 'devise'

webpackeryml
1# Note: You must restart bin/webpack-dev-server for changes to take effect
2
3default: &default
4  source_path: app/javascript
5  source_entry_path: packs
6  public_root_path: public
7  public_output_path: packs
8  cache_path: tmp/cache/webpacker
9  check_yarn_integrity: false
10  webpack_compile_output: true
11
12  # Additional paths webpack should lookup modules
13  # ['app/assets', 'engine/foo/app/assets']
14  resolved_paths: []
15
16  # Reload manifest.json on all requests so we reload latest compiled packs
17  cache_manifest: false
18
19  # Extract and emit a css file
20  extract_css: false
21
22  static_assets_extensions:
23    - .jpg
24    - .jpeg
25    - .png
26    - .gif
27    - .tiff
28    - .ico
29    - .svg
30    - .eot
31    - .otf
32    - .ttf
33    - .woff
34    - .woff2
35
36  extensions:
37    - .mjs
38    - .js
39    - .sass
40    - .scss
41    - .css
42    - .module.sass
43    - .module.scss
44    - .module.css
45    - .png
46    - .svg
47    - .gif
48    - .jpeg
49    - .jpg
50
51development:
52  <<: *default
53  compile: true
54
55  # Verifies that correct packages and versions are installed by inspecting package.json, yarn.lock, and node_modules
56  check_yarn_integrity: true
57
58  # Reference: https://webpack.js.org/configuration/dev-server/
59  dev_server:
60    https: false
61    host: localhost
62    port: 3035
63    public: localhost:3035
64    hmr: false
65    # Inline should be set to true if using HMR
66    inline: true
67    overlay: true
68    compress: true
69    disable_host_check: true
70    use_local_ip: false
71    quiet: false
72    pretty: false
73    headers:
74      'Access-Control-Allow-Origin': '*'
75    watch_options:
76      ignored: '**/node_modules/**'
77
78
79test:
80  <<: *default
81  compile: true
82
83  # Compile test packs to a separate directory
84  public_output_path: packs-test
85
86production:
87  <<: *default
88
89  # Production depends on precompilation of packs prior to booting for performance.
90  compile: false
91
92  # Extract and emit a css file
93  extract_css: true
94
95  # Cache manifest.json for performance
96  cache_manifest: true

databaseyml
1# MySQL. Versions 5.5.8 and up are supported.
2#
3# Install the MySQL driver
4#   gem install mysql2
5#
6# Ensure the MySQL gem is defined in your Gemfile
7#   gem 'mysql2'
8#
9# And be sure to use new-style password hashing:
10#   https://dev.mysql.com/doc/refman/5.7/en/password-hashing.html
11#
12default: &default
13  adapter: mysql2
14  encoding: utf8
15  pool: <%= ENV.fetch("RAILS_MAX_THREADS") { 5 } %>
16  username: root
17  password:
18  socket: /tmp/mysql.sock
19
20development:
21  <<: *default
22  database: jr_tool_development
23
24# Warning: The database defined as "test" will be erased and
25# re-generated from your development database when you run "rake".
26# Do not set this db to the same as development or production.
27test:
28  <<: *default
29  database: jr_tool_test
30
31# As with config/credentials.yml, you never want to store sensitive information,
32# like your database password, in your source code. If your source code is
33# ever seen by anyone, they now have access to your database.
34#
35# Instead, provide the password as a unix environment variable when you boot
36# the app. Read https://guides.rubyonrails.org/configuring.html#configuring-a-database
37# for a full rundown on how to provide these environment variables in a
38# production deployment.
39#
40# On Heroku and other platform providers, you may have a full connection URL
41# available as an environment variable. For example:
42#
43#   DATABASE_URL="mysql2://myuser:mypass@localhost/somedatabase"
44#
45# You can use this database configuration with:
46#
47#   production:
48#     url: <%= ENV['DATABASE_URL'] %>
49#
50production:
51  <<: *default
52  database: jr_tool_production
53  username: jr_tool
54  password: <%= ENV['JR_TOOL_DATABASE_PASSWORD'] %>

packagejson
1{
2  "name": "jr_tool",
3  "private": true,
4  "dependencies": {
5    "@rails/actioncable": "^6.0.0-alpha",
6    "@rails/activestorage": "^6.0.0-alpha",
7    "@rails/ujs": "^6.0.0-alpha",
8    "@rails/webpacker": "4.3.0",
9    "bootstrap": "^4.5.3",
10    "jquery": "^3.5.1",
11    "popper.js": "^1.16.1",
12    "turbolinks": "^5.2.0"
13  },
14  "version": "0.1.0",
15  "devDependencies": {
16    "webpack-dev-server": "^3.11.0"
17  }
18}

applicationjs
1// This file is automatically compiled by Webpack, along with any other files
2// present in this directory. You're encouraged to place your actual application logic in
3// a relevant structure within app/javascript and only use these pack files to reference
4// that code so it'll be compiled.
5require ("./jquery3")
6require ("popper")
7require ("bootstrap")
8
9
10require("@rails/ujs").start()
11require("turbolinks").start()
12require("@rails/activestorage").start()
13require("channels")
14
15
16// Uncomment to copy all static images under ../images to the output folder and reference
17// them with the image_pack_tag helper in views (e.g <%= image_pack_tag 'rails.png' %>)
18// or the `imagePath` JavaScript helper below.
19//
20// const images = require.context('../images', true)
21// const imagePath = (name) => images(name, true)