[KAFKA-9514] The protocol generator generated useless condition when a field is made nullable and flexible version is used

• Type: Bug
• Status: Resolved
• Priority: Major
• Resolution: Fixed
• Fix Version/s: 2.7.0
• Assignee: David Jacot
• Reporter: David Jacot
• Created: 06/Feb/20 09:24
• Updated: 29/Sep/20 15:29
• Resolved: 29/Sep/20 15:29

Description

The protocol generator generates useless conditions when a field of type string is made nullable after the request has been converted to using optional fields.

As an example, we have make the field `ProtocolName` nullable in the `JoinGroupResponse`. The `JoinGroupResponse` supports optional fields since version 6 and the field is nullable since version 7. Under these conditions, the generator generates the following code:

if (protocolName == null) {
 if (_version >= 7) {
   if (_version >= 6) {
     _writable.writeUnsignedVarint(0);
   } else {
     _writable.writeShort((short) -1);
  }
 } else {
   throw new NullPointerException();
 }
}

spotbugs raises an `UC_USELESS_CONDITION` because `_version >= 6` is always true.  

We could optimise the generator to handle this.
 

Issue Links

• links to: GitHub Pull Request #8793