部署在Heroku上的MERN栈项目中Material UI图标无法显示的求助

Hey there! Let's dig into why your Material UI icons are missing on Heroku even though they work perfectly on your local machine. Here are some targeted fixes and checks to resolve this issue:

1. Check Heroku Build Logs for Dependency Issues #

Sometimes Heroku's dependency installation can hit snags due to caching or network issues. You need to look beyond the runtime logs you shared and check the full build logs:

• Use the Heroku CLI to view logs: heroku logs --tail --app skillly1
• Or navigate to your app's dashboard on Heroku, go to the Activity tab, and click "View build log" for your latest deployment.
• If you see errors related to @material-ui/icons failing to install, clear Heroku's cache and redeploy:

  heroku plugins:install heroku-repo
  heroku repo:purge_cache -a skillly1
  git commit --allow-empty -m "Clear Heroku cache"
  git push heroku main
  

2. Set the PUBLIC_URL Environment Variable #

React apps in production rely on the PUBLIC_URL variable to correctly resolve static asset paths (like icons). Heroku sometimes needs this explicitly set:

• Go to your Heroku app's Settings > Config Vars, add a new variable:
  • Key: PUBLIC_URL
  • Value: https://skillly1.herokuapp.com
• Alternatively, update your package.json build script to include it:

  "scripts": {
    "build": "PUBLIC_URL=https://skillly1.herokuapp.com react-scripts build"
  }
  

3. Align Material UI Package Versions #

You're using @material-ui/core@4.11.0 and @material-ui/icons@4.11.2—while minor version differences usually work, mismatches can occasionally cause rendering issues. Sync the versions:

• Update your package.json dependencies:

  "@material-ui/core": "^4.11.2",
  "@material-ui/icons": "^4.11.2"
  

• Delete node_modules and package-lock.json, run npm install locally, then redeploy to Heroku.

4. Verify Static Asset Serving on Your Backend #

If your Express backend is serving the React build, make sure it's correctly pointing to the static assets:

• Check your server file (e.g., server.js) for code like this:

  const path = require('path');
  if (process.env.NODE_ENV === 'production') {
    // Serve static files from the React build folder
    app.use(express.static(path.join(__dirname, 'client/build')));
    
    // Catch all routes and return the React app
    app.get('*', (req, res) => {
      res.sendFile(path.join(__dirname, 'client/build', 'index.html'));
    });
  }
  

• Adjust the path if your React build is in a different location (e.g., path.join(__dirname, 'build') if your frontend is in the root directory).

5. Test the Production Build Locally #

Rule out Heroku-specific issues by testing your production build on your machine:

• Run npm run build to create the production bundle.
• Serve the build folder with a static server: npx serve -s build
• If icons are missing here too, the problem is in your local build configuration. Double-check your icon imports (they look correct in your code) and ensure no CSS styles are hiding or overriding the icons.

内容的提问来源于stack exchange，提问作者Yash Sethia