Code splitting for Kotlin/JS browser apps

This is a rough proof-of-concept that a Kotlin/JS browser app can be split into multiple chunks that can depend on each other dynamically. For example a Kotlin React app could be split into multiple smaller JS files that way.

Architecture

Modules

• / compiles all submodules into separate JS files.
• /modules/dynamic will be loaded dynamically.
• /modules/index is the entry point with a main() function that loads dynamic dynamically.
• /modules/shared will be shared by dynamic and index without duplicating code.

Configuration

• /webpack.config.d/entry.js defines the index module as the entry point for the library.
• /build.gradle.kts makes various changes to the compilation:
  • Disable klib production (-Xir-produce-klib-dir) that would typically result in just a single JS file.
  • Create per-module JS files -Xir-per-module and -Xir-produce-js.
  • Manually copy these created JS files to the appropriate NPM project directory.
  • Disable IR link tasks that don't seem to be needed anymore.

Known limitations

• Only works with the JS IR compiler.
• The setup is fragile and can break with subsequent Kotlin updates.
• Dynamic imports have weird names (like kotlin_kjs_chunks_dynamic in this example).
• Only @JsExport exports of dynamic modules can be used. Adding dynamic as a Gradle dependency for index for example to make its symbols accessible would turn it into a static import.