func MapExec[T, S any]()

in table/internal/utils.go [489:540]

• 44 lines of code
• 10 McCabe index (conditional complexity)

func MapExec[T, S any](nWorkers int, slice iter.Seq[T], fn func(T) (S, error)) iter.Seq2[S, error] {
	if nWorkers <= 0 {
		nWorkers = runtime.GOMAXPROCS(0)
	}

	var g errgroup.Group
	ch := make(chan T, nWorkers)
	out := make(chan S, nWorkers)

	for range nWorkers {
		g.Go(func() error {
			for v := range ch {
				result, err := fn(v)
				if err != nil {
					return err
				}
				out <- result
			}

			return nil
		})
	}

	var err error
	go func() {
		defer close(out)
		for v := range slice {
			ch <- v
		}
		close(ch)
		err = g.Wait()
	}()

	return func(yield func(S, error) bool) {
		defer func() {
			// drain out if we exit early
			for range out {
			}
		}()

		for v := range out {
			if !yield(v, nil) {
				return
			}
		}

		if err != nil {
			var z S
			yield(z, err)
		}
	}
}