Rollup warning: The 'this' keyword is equivalent to 'undefined' at the top level of an ES module, and has been rewritten

[saraedum]

When building a vue-facing-decorator project with rollup, I get:

vue-facing-decorator/dist/esm/option/emit.js (1:17): The 'this' keyword is equivalent to 'undefined' at the top level of an ES module, and has been rewritten

This is with version 4.0.1 (but also with earlier versions I tested.)

This is a harmless warning. When this is undefined, the code uses the intended fallback. Still this shows up in vite build logs.

I can provide a reproducer if this is helpful.