With Rollup, calling watcher.close() immediately fires the "close" event and resolves its returned promise, and any in-progress build is stopped (no bundle.js is created).

With Rolldown, calling watcher.close() waits until the current in-progress build is done and written to disk before firing the "close" event and resolving the returned promise (bundle.js is created).

It is confusing to me that calling Rolldown's watcher.close() does not prevent an in-progress build from being written to disk.

Example in this repo. You can see that Rolldown still emits BUNDLE_END and END even after watcher.close() is called, but Rollup does not.

$ node rollup.js
START
BUNDLE_START
[delay-plugin] sleeping 2000ms
call watcher.close
close event
watcher.close promise resolves

$ node rolldown.js
START
BUNDLE_START
[delay-plugin] sleeping 2000ms
call watcher.close
BUNDLE_END
END
close event
watcher.close promise resolves