[KAFKA-2599] Metadata#getClusterForCurrentTopics can throw NPE even with null checking

• Type: Bug
• Status: Resolved
• Priority: Minor
• Resolution: Fixed
• Affects Version/s: 0.8.2.1
• Fix Version/s: 0.9.0.0
• Component/s: clients
• Assignee: Edward Ribeiro
• Reporter: Edward Ribeiro
• Reviewer: Guozhang Wang
• Created: 29/Sep/15 20:46
• Updated: 06/Oct/15 20:35
• Resolved: 06/Oct/15 20:35

Description

While working on another issue I have just seen the following:

    private Cluster getClusterForCurrentTopics(Cluster cluster) {
        Collection<PartitionInfo> partitionInfos = new ArrayList<>();
        if (cluster != null) {
            for (String topic : this.topics) {
                partitionInfos.addAll(cluster.partitionsForTopic(topic));
            }
        }
        return new Cluster(cluster.nodes(), partitionInfos);
    }

Well, there's a null check for cluster, but if cluster is null it will throw NPE at the return line by calling cluster.nodes()! So, I put together a quick fix and changed MetadataTest to reproduce this error.