private boolean emitCachedSignals() {
            if (error != null) {
                try {
                    requiredWriteSubscriber().onError(error);
                } finally {
                    releaseCachedItem();
                }
                return true;
            }
            final T item = this.item;
            this.item = null;
            if (item != null) {
                requiredWriteSubscriber().onNext(item);
            }
            if (completed) {
                requiredWriteSubscriber().onComplete();
                return true;
            }
            return false;
        }
The actual writeSubscriber from the HTTP server adapter.
spring/boot3-webflux-autoconfigure/src/main/java/com/linecorp/armeria/spring/web/reactive/ChannelSendOperator.java