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

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Details

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

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.