Change Shared Modules package to net.thunderbird

• Issue: #9012

Status

• Accepted

Context

The Thunderbird Android project is a white-label version of K-9 Mail, and both apps — app-thunderbird and app-kmail — coexist in the same repository. They have distinct application IDs and branding, but share a significant portion of the code through common modules.

These shared modules currently use the app.k9mail or com.fsck package name, which are legacy artifacts from K-9 Mail. While K-9 will remain available for some time, the project’s primary focus has shifted toward Thunderbird.

To reflect this shift, establish clearer ownership, and prepare for future development (including cross-platform code integration), we will rename the packages in shared modules from app.k9mail and com.fsck to net.thunderbird. The actual application IDs and package names of app-thunderbird and app-k9mail must remain unchanged.

Decision

We decided to rename the base package in all shared modules from app.k9mail and com.fsck to net.thunderbird.

Specifically:

• All Kotlin/Java packages in shared modules will be refactored to use net.thunderbird as the base
• This must not affect the application IDs or packages of app-thunderbird or app-kmail, which will remain as-is
• All references, imports, and configuration references will be updated accordingly
• Tests, resources, and Gradle module settings will be adjusted to match the new package structure

This change will establish a clearer identity for the shared code, align with Thunderbird's branding, and prepare the project for cross-platform development.

Consequences

Positive Consequences

• Shared code reflects Thunderbird branding and identity
• Reduces confusion when navigating codebase shared by both apps
• Sets the foundation for cross-platform compatibility and future modularization
• Helps reinforce long-term direction of the project toward Thunderbird

Negative Consequences

• Large-scale refactoring required across multiple modules
• Risk of introducing regressions during package renaming
• Potential for disruption in local development setups (e.g., IDE caching, broken imports)
• Contributors familiar with the old structure may need time to adjust