Heroku部署失败求助：Rails应用推送时提示未检测到默认语言

Hey there, I’ve run into this exact issue before with Rails apps on Heroku—let’s walk through the most likely fixes since you’ve already tried adding the Ruby buildpack:

• Double-check your root directory files
  Heroku relies on Gemfile and Gemfile.lock in your project’s root to detect Ruby. Make sure these files aren’t nested in a subfolder (like src/ or something). Also, confirm your Gemfile has a Ruby version specified (e.g., ruby '3.2.2') and that you’ve run bundle install locally to generate a valid Gemfile.lock (don’t skip this step—Heroku needs the lock file to resolve dependencies).

• Force-set the Ruby buildpack and re-deploy
  Sometimes just adding the buildpack isn’t enough; you need to explicitly set it as the default. Run these commands in your terminal:

  heroku buildpacks:set heroku/ruby
  git commit --allow-empty -m "Set Ruby buildpack as default"
  git push heroku main
  

  The empty commit triggers a fresh deployment so Heroku picks up the new buildpack setting.

• Check your .gitignore file
  Accidentally adding Gemfile.lock to .gitignore is a super common mistake. Open your .gitignore and make sure there’s no line for Gemfile.lock. If there is, remove it, then run:

  git add Gemfile.lock
  git commit -m "Add Gemfile.lock to repo"
  git push heroku main
  

• Purge Heroku’s build cache
  Old cache can sometimes interfere with language detection. Clear it with:

  heroku repo:purge_cache
  git push heroku main
  

  This forces Heroku to re-run the entire build process from scratch, which often fixes detection issues.

• Verify buildpack order (if using multiple buildpacks)
  If your app uses other buildpacks (like for assets or add-ons), make sure the Ruby buildpack is listed first. Run heroku buildpacks to check the order, and adjust with:

  heroku buildpacks:add --index 1 heroku/ruby
  

If none of these work, pull the full deployment logs with heroku logs --tail right after a failed push—there might be a subtle error (like a corrupted Gemfile.lock) that the initial error message isn’t showing.

内容的提问来源于stack exchange，提问作者Didymus Orotayo