部署Express.js+React.js项目到Heroku时遇模块缺失错误求助

Hey there, let's get your app up and running on Heroku quickly—your error log tells us exactly what's going wrong here.

The Root Cause #

Looking at your logs, the critical line that's breaking your deployment is:

Error: Cannot find module './school'

This almost always happens for one of two simple reasons:

1. Case sensitivity mismatch: Local development (especially on Windows) uses a case-insensitive file system, so require('./school') will find School.js or SCHOOL.js just fine. But Heroku runs on Linux, which is strictly case-sensitive—so the filename has to match exactly what's in your require statement.
2. Missing file in Git: The school.js file exists on your local machine, but you never added or committed it to Git, so it doesn't get pushed to Heroku during deployment.

Step-by-Step Fixes #

1. Verify File Existence & Case Matching #

• Navigate to your controllers directory and check the exact filename of your school controller. Is it school.js, School.js, or something else?
• Open /controllers/index.js (the file throwing the error) and look at the first require statement—it should look like:

  const schoolController = require('./school');
  

  Make sure the path here matches your actual filename exactly (including uppercase/lowercase letters). If your file is School.js, update the require to require('./School'), or rename the file to school.js to match the existing require statement.

2. Ensure the File is Committed to Git #

• Run git status in your project root. Look for any untracked files—if school.js (or your renamed file) is listed, it means it hasn't been added to Git yet.
• Add and commit the file:

  git add controllers/school.js  # Replace with your actual file path
  git commit -m "Add missing school controller file"
  

3. Re-deploy to Heroku #

• Push your updated code to Heroku:

  git push heroku main  # Use "master" instead of "main" if that's your default branch
  

• Once deployment finishes, check the logs again with heroku logs --tail to confirm the module error is gone. Then visit your app at xxxxx.herokuapp.com—it should no longer show the "Application error" page.

Extra Tips for Heroku Deployment #

• Always double-check case sensitivity for all file paths when deploying to Linux-based platforms like Heroku—this is a super common gotcha!
• Make sure all backend dependencies are listed in your package.json (Heroku installs only what's in this file).
• For your PostgreSQL/Sequelize setup later, ensure your app is using Heroku's DATABASE_URL environment variable instead of local credentials.

内容的提问来源于stack exchange，提问作者Idan