【解決】Your Yarn packages are out of date! Please run `yarn install` to update.

yarn installするとYour Yarn packages are out of date! Please run yarn install to update.（あなたのヤーンパッケージは古くなっています！更新するには yarn install を実行してください）の解決策。エラー文通りyarn installしたんだけど、なんだこれイタチごっこじゃん、、、

エラー文

========================================
  Your Yarn packages are out of date!
  Please run `yarn install` to update.
========================================


To disable this check, please add `config.webpacker.check_yarn_integrity = false`
to your Rails development config file (config/environments/development.rb).


yarn check v1.16.0
error Lockfile does not contain pattern: "bootstrap@^4.3.1"
error Lockfile does not contain pattern: "jquery@^3.4.1"
error Couldn't find an integrity file
error Found 3 errors.
info Visit https://yarnpkg.com/en/docs/cli/check for documentation about this command.

解決策

node_modulesを削除

$ rm -rf node_modules/

yarn.lockファイルを削除

$ rm -rf yarn.lock

yarnをインストール

$ yarn install

yarnをアップグレード

$ yarn upgrade

あとはサーバー起動できれば

$ rails s

以上です！

https://qiita.com/nakki/items/4fa58cb6ff4d6c24c2d2
https://classic.yarnpkg.com/en/docs/cli/upgrade/
https://motomichi-works.hatenablog.com/entry/2020/04/23/115936