Angular Upgrade

 

1. Pre-Upgrade Considerations

• Back Up the Project: Before starting the upgrade, ensure you have a complete backup of your project, either via version control (e.g., GIT) or by creating a local backup.
• Check Compatibility: Review the breaking changes for both Angular 16 and 17 using the Angular Update Guide. For large projects, there may be many APIs or dependencies that need adjustment.
• Break Down the Upgrade: Consider upgrading in stages instead of all at once. For example, you can upgrade Angular and its core packages first, and then handle third-party libraries and other dependencies afterward.

2. Use a Dedicated Branch

Create a new branch for the upgrade, so the main project development is not disturbed:

bash
 
git checkout -b upgrade/angular-15-to-17

3. Upgrade to Angular 16 First

Perform the upgrade to Angular 16 in smaller, manageable steps.

• Upgrade Core and CLI to Angular 16:

  bash
   
  ng update @angular/core@16 @angular/cli@16
  

• Upgrade Other Core Libraries (e.g., @angular/material, @angular/forms):

  bash
   
  ng update @angular/material@16
  

• Test After Each Step: After upgrading, run the application and tests to ensure the system remains functional. With large projects, it’s important to check for regressions after each significant step:

  bash
   
  ng serve
  ng test
  

4. Break the Project into Modules

If your project is modular (using Angular’s NgModules), tackle one module at a time:

• Upgrade specific feature modules by focusing on one part of the app at a time.
• Test each module in isolation after upgrading it to ensure that there are no issues before moving to the next module.

5. Handle Third-Party Dependencies

Large projects often depend on third-party libraries. Ensure these are compatible with Angular 16 before the next upgrade. Use the following steps:

• Update All Dependencies: Use npm outdated to check for any packages that need updating:

  bash
   
  npm outdated
  npm install <package>@latest
  

• Check for Angular Compatibility: Ensure each package supports Angular 16 and 17. Check each library’s changelog or GitHub repository for compatibility notes.

6. Upgrade to Angular 17

After successfully upgrading and testing Angular 16, proceed with the upgrade to Angular 17:

• Upgrade Core and CLI to Angular 17:

  bash
   
  ng update @angular/core@17 @angular/cli@17
  

• Upgrade Other Angular Packages:

  bash
   
  ng update @angular/material@17
  

7. Fix and Refactor Deprecations

For large projects, there will likely be multiple deprecated APIs that need refactoring. Tools like Angular ESLint or TSLint (if you're using it) can help catch these issues:

• Enable strict mode in TypeScript (strictTemplates in tsconfig.json) to identify problematic areas.
• Fix or refactor code as per Angular's deprecation warnings. If possible, automate some of the code refactoring using tools like angular-eslint.

8. Run Incremental Tests

After upgrading, follow an incremental testing strategy:

• Unit Tests: Run unit tests for the entire project using ng test. Ensure all tests pass after each stage of the upgrade.
• End-to-End Tests: Run E2E tests using ng e2e to ensure that the entire application is still functional after the upgrade.
• Manual Testing: Conduct manual testing for critical parts of the application to detect any subtle issues that automated tests may miss.

9. Resolve Potential Issues

• Performance Issues: Large projects may experience performance bottlenecks after an upgrade due to changes in build tooling or dependency optimization. Use Webpack's bundle analyzer to investigate large bundle sizes and refactor accordingly:

  bash
   
  ng build --prod --stats-json
  npx webpack-bundle-analyzer dist/stats.json
  

• Outdated Dependencies: If any third-party library is incompatible with Angular 17, check if the library is actively maintained. If not, consider finding alternatives or implementing a workaround.

10. Finalize the Upgrade

• Once the Angular 17 upgrade is complete and the project is stable, merge the changes back to your main branch:

  bash
   
  git checkout main
  git merge upgrade/angular-15-to-17
  

• Clean the Project: Clear cache and node modules:

  bash
   
  npm cache clean --force
  rm -rf node_modules
  npm install
  

11. Deploy and Monitor

After the upgrade, deploy the application to a staging environment first. Monitor performance, error logs, and user feedback before deploying to production.

12. Build for Production

Finally, verify the production build with:

bash
 
ng build --prod

Summary

• Work in Stages: Upgrade from Angular 15 to 16 first, and then to 17. Test after each step to avoid overwhelming issues.
• Module-Based Upgrade: For large projects, divide the work by upgrading modules and dependencies incrementally.
• Test Continuously: Ensure that unit and end-to-end tests are run frequently throughout the upgrade process.
• Backup and Branching: Use Git branches for managing the upgrade to avoid disrupting the main development work.

This approach helps mitigate risks in large projects and ensures a smoother upgrade.