Safely Upgrading or Rolling Back Ceylon: Practical Steps and Verification

Assumptions: Because the official Ceylon repository was archived on April 13, 2023, and is now read-only, no new official releases are being published. Any upgrade or rollback must rely on existing archived artifacts or local backups. Specific Java version requirements are not provided in the source text; however, a compatible Java Development Kit (JDK) is a standard prerequisite for Ceylon.

1. Prerequisites
   • Java Compatibility: Ensure a compatible JDK is installed and configured in your system path.
   • System Backup: Create a full backup of your current Ceylon installation directory (e.g., $CEYLON_HOME) and your local module repository (typically ~/.ceylon/repo) to prevent data loss during the transition.
   • Disk Space: Ensure sufficient storage to maintain a side-by-side installation of the old and new versions.
2. Downloading and Installing the New Release
   • Locate Artifacts: Since the repository is archived, retrieve the desired version's binary distribution from the eclipse-archived/ceylon GitHub releases or a trusted mirror.
   • Extraction: Extract the downloaded archive to a unique directory (e.g., /opt/ceylon-new) to avoid overwriting the stable installation.
   • Environment Configuration: Update your CEYLON_HOME environment variable and add the bin directory to your system PATH to point to the new installation.
3. Verifying the Installation
   • Version Check: Execute ceylon version to confirm the installation matches the intended release.
   • Compiler Functionality: Run a simple "Hello World" program using ceylon run to verify the compiler is operational.
   • Module Resolution: Attempt to compile an existing project that depends on external modules to ensure the modular distribution layout and repository links are functioning correctly.
4. Rolling Back to a Previous Version
   • Revert Path: If verification fails, immediately change the CEYLON_HOME and PATH variables back to the original backup directory.
   • Restore Repository: If the module repository was corrupted, restore it from the backup created in the prerequisites step.
   • Final Check: Run ceylon version and a test compilation to confirm the environment has returned to a stable state.

To ensure existing modules do not break, perform a "dry run" by compiling your project in a separate directory with the new version before updating your primary environment. Compare the resulting bytecode or JAR files against the previous version to detect unexpected changes in behavior or resolution.