Batch producing messages only works is all messages are on the same topic

[sash]

Looking at the code I can see that when using producer->sendBatch, the topic is read from the batch itself, but in the documentation I'm left with the impression that the batch itself does NOT have to have a topic. In the look the messages topic is even actively overwritten.

public function produceBatch(MessageBatch $messageBatch): int
    {
        if ($messageBatch->getTopicName() === '') {
            throw CouldNotPublishMessageBatch::invalidTopicName($messageBatch->getTopicName());
        }

        $topic = $this->producer->newTopic($messageBatch->getTopicName()); # << Topic is resolved from the Batch instance itself

        $messagesIterator = $messageBatch->getMessages();

        $messagesIterator->setIteratorMode(SplDoublyLinkedList::IT_MODE_FIFO);

        $produced = 0;

        $this->dispatcher->dispatch(new PublishingMessageBatch($messageBatch));

        foreach ($messagesIterator as $message) {
            assert($message instanceof Message);
            $message->onTopic($messageBatch->getTopicName()); # << Topic in message batch is overwritten!
            $message = $this->serializer->serialize($message);

            $this->produceMessageBatch($topic, $message, $messageBatch->getBatchUuid());

            $this->producer->poll(0);

            $produced++;
        }

        $this->flush();

        $this->dispatcher->dispatch(new MessageBatchPublished($messageBatch, $produced));

        return $produced;
    }

My idea it to update the documentation and make note of that fact. What do you guys think?

[mateusjunges]

Hey @sash this looks like a bug to me. I opened #313 to fix it