Investigate converting `rsdroid[-testing]` to a `java-library`

[david-allison]

• Speeds up tests
  • This is more useful now we're considering re-architecting the module structure of the app. If we can remove 'Robolectric' from a test suite for a module, we get huge savings. There are many tests which only use Robolectric due to the rsdroid/libanki, but we can't feasibly
• Fixes local builds: Direct local .aar file dependencies are not supported when building an AAR.
  • can't compile ankidroid using local_backend #671
  • This does not impact androidTest
• I was asked in the past about this for a university project. It seemed feasible at the time, but I didn't have capacity.

Initial thoughts

1. What are the blockers? (database; Looper etc...)
   • I do not believe these will cause significant problems.
2. How will packaging the .so files work?
   • We currently have two artifacts: rsdroid with .so files for each of the 4 mainstream Android targets.
   • rsdroid-testing with rsdroid.dll, librsdroid.dylib and librsdroid.so for Robolectric
     • Loaded via RustBackendLoader
3. Document build/generated/anki_artifacts

• Used via AssetManager - mmap onto the apk

Constraints

• Bloating the apk size (fat JAR) is unacceptable
• Local aar -> aar references are unacceptable
  • apk -> local aar
• anki_artifacts are heavily latency sensitive: Pages and web content used by the study screen

[david-allison]

How will packaging the .so files work?

I've ideated with Claude, and I feel the best solution will be:

• net.ankiweb:rsdroid:<v> - java-library JAR - depended on by the dependency tree of Anki-Android
• net.ankiweb:rsdroid-android:<v> - AAR containing only the per-Android .so files and anki_artifacts. Depended on by the app module and androidTest tests
  • anki_artifacts requires an AssetManager to use the files, which is an Android dependency
    • TBC - is this going to cause a problem with aar dependencies
• net.ankiweb:rsdroid-desktop:<v> - java-library JAR containing librsdroid.dylib / librsdroid.so / rsdroid.dll + BackendLoader