Creating a checklist for migrating a Joomla Component Build (JCB) component from Joomla 3 to Joomla 4 involves ensuring that both the auto-generated code from JCB and any custom code or fields you've added are updated to be compatible with Joomla 4's architecture, namespaces, and field types. Here's an checklist to guide you through this process:

1. Backup Your Component

• Ensure you have a complete backup of your Joomla 3 component.

2. Update to the Latest JCB Version

• Make sure you have the latest version of JCB that supports Joomla 4.

3. Review JCB Generated Files

• File Structure Changes: Verify that JCB has correctly updated the file structure to Joomla 4 format.
• Namespace Implementation: Check the namespace declarations in all PHP files.

4. Update Custom Code

• Namespace Compatibility: Ensure custom PHP classes use the correct namespaces.
• Class and Method Updates: Refactor any deprecated classes and methods.
• Database Query Changes: Update database queries to use Joomla 4's improved query methods.

5. Modify XML Files

• Manifest File: Update the extension's manifest file for Joomla 4 compatibility.
• Language Files: Ensure language files follow Joomla 4's new standards.

6. Review and Update Field Types

• Standard Field Types: Update any standard field types that have changed in Joomla 4.
• Custom Field Types: Modify custom fields to ensure they are Joomla 4 compatible.

7. JavaScript and CSS Adjustments

• Media Versioning: Adapt to Joomla 4's media versioning system.
• Library Updates: Update any third-party libraries (e.g., jQuery) to versions compatible with Joomla 4.

8. Testing in Joomla 4 Environment

• Frontend Testing: Check all views, forms, and functionalities in the frontend.
• Backend Testing: Test all administrative functionalities.
• Debugging and Logging: Utilize Joomla 4's improved debugging and logging capabilities.

9. Performance and Security Checks

• Optimize Queries: Ensure database queries are optimized for performance.
• Security Best Practices: Review custom code for Joomla 4's security best practices.

10. Update Documentation and Help Screens

• User Documentation: Update any user guides or documentation.
• Help Screens: Ensure help screens are accurate for Joomla 4.

11. Community and Support

• Joomla Forum: Check the Joomla forums for any component-specific migration tips.
• JCB Support: Utilize JCB issues for any migration issues specific to JCB-generated code.

12. Final Review and Launch

• User Acceptance Testing: Conduct thorough testing with end-users.
• Backup: Create a final backup before going live.
• Go Live: Deploy the component to your live Joomla 4 site.

Additional Resources

• Joomla 4 Migration Guide: Refer to the official Joomla documentation for migration.

By following this checklist, you can systematically upgrade your Joomla 3 component to Joomla 4, ensuring both the JCB-generated parts and your custom additions are fully compatible with the new Joomla architecture and standards.