The Rspack docs state that when merging configurations array are concatenated, https://rspack.rs/config/extends#:~:text=Arrays%20are%20concatenated

The behavior shown in this repo is that the plugins from the extended config are dropped, unless you add '...' to the plugins array. As far as I can find '...' in plugins is undocumented behavior, and while it works it isn't allowed with Rspack's config types.

1. yarn
2. yarn rspack serve
3. Observe that MyPlugin: The Rspack build process is starting! is in the output, but MyBasePlugin: The Rspack build process is starting! is not.
4. yarn tsc -> no type errors
5. In rspack.config.ts uncomment the ... in plugins.
6. yarn rspack serve
7. Observe that the output from both plugins is present.
8. yarn tsc -> Type '"..."' is not assignable to type 'Plugin'.