Reducer does not return an error when the original stream has only 1 item

[vadimi]

Hello, thanks for the awesome library. I'm hitting an issue with the reducer that doesn't return an error when the original stream has only 1 item and the intermediate step returns it. Here is a quick reproduction:

items := rill.FromSlice([]int{1}, nil)
mappedItems := rill.Map(items, 1, func(item int) (int, error) {
	return 0, fmt.Errorf("an error occurred at item %d", item)
})
_, _, err := rill.Reduce(mappedItems, 1, func(prev, current int) (int, error) {
	return 0, nil
})
fmt.Println("done")
fmt.Println(err)

The error is nil in this case.

I was digging into the code a bit and it looks like the line setReturns(res.Value, ok, nil) ignores the error. Should it be something like this instead? setReturns(res.Value, ok, res.Error)?

[destel]

Hello. Thanks for reporting this and thanks for being a user of rill.
I confirm the bug, and will try to publish a fix within a few hours today