What problem does this feature solve?

The primary purpose for this feature is to improve testability of Vue single file components. With named exports it is possible to have both a default export of the component with all dependencies assigned as well as a named constructor function export which would allow substitutes to be injected.

This avoids the need to use things like the inject-loader.

There are probably other use cases for supporting named exports, but testability is the primary one for me.

Related discussion on the forum: https://forum.vuejs.org/t/vue-loader-proposal-to-support-named-exports-for-testability

What does the proposed API look like?

<script>
import dep1 from 'dep1'
import dep2 from 'dep2'

export function component(dep1, dep2) {
   ...
   return {
      properties: {},
      data() { },
      methods: {},
      ...
   };
}

export default component(dep1, dep2);
</script>