Rails6.0.3アプリのherokuデプロイ時のエラーについて

Question

Railsチュートリアル第6版を参考にherokuにrailsアプリをデプロイすると、以下のエラーが発生しました。
webpackやnodeのコンフリクトでエラーが起きているのかと思いますが、エラー内容で検索しても該当のものが見当たらないため、解決方法を教えていただきたいです。

ローカル環境

• macOS Big Sur 11.2.3
• ruby 2.6.3
• Rails 6.0.3
• Bundler 1.17.2
• yarn 1.22.10
• npm 7.7.6

##エラー内容

$git push heroku master
略
remote:        Bundle completed (38.81s)
remote:        Cleaning up the bundler cache.
remote: -----> Installing node-v12.16.2-linux-x64
remote: -----> Installing yarn-v1.22.4
remote: -----> Detecting rake tasks
remote: -----> Preparing app for Rails asset pipeline
remote:        Running: rake assets:precompile
remote:        yarn install v1.22.4
remote:        [1/4] Resolving packages...
remote:        [2/4] Fetching packages...
remote:        info fsevents@1.2.13: The platform "linux" is incompatible with this module.
remote:        info "fsevents@1.2.13" is an optional dependency and failed compatibility check. Excluding it from installation.
remote:        [3/4] Linking dependencies...
remote:        warning " > webpack-dev-server@3.11.2" has unmet peer dependency "webpack@^4.0.0 || ^5.0.0".
remote:        warning "webpack-dev-server > webpack-dev-middleware@3.7.3" has unmet peer dependency "webpack@^4.0.0 || ^5.0.0".
remote:        [4/4] Building fresh packages...
remote:        Done in 15.90s.
remote:        I, [2021-04-14T14:16:56.255745 #1065]  INFO -- : Writing /tmp/build_b3c6e1ab/public/assets/application-e3b0c44298fc1c149afbf4c8996fb92427ae41e4649b934ca495991b7852b855.css
remote:        I, [2021-04-14T14:16:56.256613 #1065]  INFO -- : Writing /tmp/build_b3c6e1ab/public/assets/application-e3b0c44298fc1c149afbf4c8996fb92427ae41e4649b934ca495991b7852b855.css.gz
remote:        Compiling…
remote:        Compilation failed:
remote:        [webpack-cli] Failed to load '/tmp/build_b3c6e1ab/config/webpack/production.js' config
remote:        [webpack-cli] TypeError: Cannot read property 'toWebpackConfig' of undefined
remote:            at Object.<anonymous> (/tmp/build_b3c6e1ab/config/webpack/production.js:5:30)
remote:            at Module._compile (/tmp/build_b3c6e1ab/node_modules/v8-compile-cache/v8-compile-cache.js:192:30)
remote:            at Object.Module._extensions..js (internal/modules/cjs/loader.js:1176:10)
remote:            at Module.load (internal/modules/cjs/loader.js:1000:32)
remote:            at Function.Module._load (internal/modules/cjs/loader.js:899:14)
remote:            at Module.require (internal/modules/cjs/loader.js:1042:19)
remote:            at require (/tmp/build_b3c6e1ab/node_modules/v8-compile-cache/v8-compile-cache.js:159:20)
remote:            at loadConfig (/tmp/build_b3c6e1ab/node_modules/webpack-cli/lib/webpack-cli.js:1322:31)
remote:            at /tmp/build_b3c6e1ab/node_modules/webpack-cli/lib/webpack-cli.js:1409:74
remote:            at Array.map (<anonymous>)
remote:
remote:
remote:  !
remote:  !     Precompiling assets failed.
remote:  !
remote:  !     Push rejected, failed to compile Ruby app.
remote:
remote:  !     Push failed
remote: Verifying deploy...
remote:
remote: !	Push rejected to xxxx.
remote:

#Gemfile

source 'https://rubygems.org'
git_source(:github) { |repo| "https://github.com/#{repo}.git" }

gem 'rails',      '6.0.3'
gem 'puma',       '4.3.6'
gem 'sass-rails', '5.1.0'
gem 'webpacker',  '4.0.7'
gem 'turbolinks', '5.2.0'
gem 'jbuilder',   '2.9.1'
gem 'bootsnap',   '1.4.5', require: false

group :development, :test do
  gem 'sqlite3', '1.4.1'
  gem 'byebug',  '11.0.1', platforms: [:mri, :mingw, :x64_mingw]
end

group :development do
  gem 'web-console',           '4.0.1'
  gem 'listen',                '3.1.5'
  gem 'spring',                '2.1.0'
  gem 'spring-watcher-listen', '2.0.1'
end

group :test do
  gem 'capybara',           '3.28.0'
  gem 'selenium-webdriver', '3.142.4'
  gem 'webdrivers',         '4.1.2'
end

group :production do
  gem 'pg', '1.1.4'
end

#package.json

{
  "name": "StretchTimer",
  "private": true,
  "dependencies": {
    "@rails/actioncable": "^6.0.0",
    "@rails/activestorage": "^6.0.0",
    "@rails/ujs": "^6.0.0",
    "@rails/webpacker": "^6.0.0-beta.6",
    "turbolinks": "^5.2.0"
  },
  "version": "0.1.0",
  "devDependencies": {
    "webpack-dev-server": "^3.11.2"
  }
}

Answer 1

package.json を見ると

"@rails/webpacker": "^6.0.0-beta.6",

になってますが、 6.x 系には toWebpackConfig が存在しないためエラーになっています。

5.x 系にダウングレードするか、
または下記のアップグレードガイドに従うと良いと思います。

"To webpacker v6 from v5" at rails/webpacker | Github

Comments

[gunjo2000]

webpackerを6.0.0に上げた覚えがなかったため、おや?と思い再び
$rails new app
から生成してみたところ、package.json内が
"@rails/webpacker": "4.3.0",
となっていたため、試しにherokuへデプロイしてみたところ、すんなり成功しました。どの操作で6.0.0に上がっていたかは謎のままですが、ご回答ありがとうございました。