[FLINK-25513] CoFlatMapFunction requires both two flat_maps to yield something

• Type: Bug
• Status: Closed
• Priority: Major
• Resolution: Fixed
• Affects Version/s: 1.13.0
• Fix Version/s: 1.13.6, 1.14.3, 1.15.0
• Component/s: API / Python
• Labels: pull-request-available
• Assignee: chendan
• Reporter: chendan
• Created: 04/Jan/22 08:36
• Updated: 06/Jan/22 11:36
• Resolved: 06/Jan/22 11:36

Description

When I used CoFlatMapFunction in pyflink, I found out that I must put yield something in both flat_map1 and flat_map2. Otherwise, it will raise an exception: TypeError: 'NoneType' object is not iterable.

In pyflink source code: datastream.py,  the process_element2 of KeyedCoMapCoProcessFunction class in ConnectedStreams class has only one sentence: 

yield self._underlying.map2(value). if the flat_map2 has not yield something it will result in exception. So it should judge whether the self._underlying.map2(value) is None or not firstly.

Issue Links

• links to: GitHub Pull Request #18280