Improve treeshaking of compiled/published multi-component files

[wessberg]

Problem

If we have a file like this:

// module-a

class MyComponent1 { ... }
___registerElement("my-component-1", MyComponent1);
class MyComponent2 { ... }
___registerElement("my-component-2", MyComponent2);

...And we make an import like this:

// module-b
import {MyComponent1} from "./module-a";

...MyComponent2 won't be treeshaken with for example Rollup, since the calls to "___registerElement" may have side effects.

This is unfortunate since this may lead to scenarios with files exporting many components none of which will be treeshaken.

Solution

[WIP]

Rather than declare the static helper calls inside the top-level scope of files declaring components, the helper calls should be embedded within the class-scope of the components.

One way to do so is to place all of them inside the already-defined static bootstrap method of components.

One last thing that is then needed is to avoid calling ___bootstrap from the top-level scope, but instead have the component itself do that somehow.