raams95 opened a new issue, #40562: URL: https://github.com/apache/beam/issues/40562
### What happened? `beam.Regex.all_matches` is documented to return all groups of a matching element, but it builds the output with `range(m.lastindex + 1)`: https://github.com/apache/beam/blob/d9e99ad211f/sdks/python/apache_beam/transforms/util.py#L2166-L2169 `Match.lastindex` is not the number of groups. It is the index of the last group that matched, and for nested groups it is the outer group that closed last. It is `None` when the regex has no groups. So: ```python import apache_beam as beam with beam.Pipeline() as p: _ = ( p | beam.Create(['ab']) | beam.Regex.all_matches(r'((a)(b))') | beam.Map(print)) # prints ['ab', 'ab'] expected ['ab', 'ab', 'a', 'b'] with beam.Pipeline() as p: _ = ( p | beam.Create(['a']) | beam.Regex.all_matches(r'(a)(b)?') | beam.Map(print)) # prints ['a', 'a'] expected ['a', 'a', None] with beam.Pipeline() as p: _ = ( p | beam.Create(['aaa']) | beam.Regex.all_matches(r'a+') | beam.Map(print)) # TypeError: unsupported operand type(s) for +: 'NoneType' and 'int' # [while running 'all_matches(a+)/FlatMap(_process)'] ``` So the output has a different number of groups depending on which optional groups matched, nested groups are lost, and a regex without groups fails the pipeline. Expected: one entry for the entire match, then one per group of the regex (`None` for a group that did not take part in the match), which is what Java's `Regex.AllMatches` does (it loops over `0..groupCount()` and adds `null` for such groups). This is the same kind of problem as the one fixed for `Regex.find_all(..., Regex.ALL)` in #40399. Reproduced on master at d9e99ad211f (Python 3.12, DirectRunner). The code has been the same since the transform was added. ### Issue Priority Priority: 2 (default / most bugs should be filed as P2) ### Issue Components - [x] Component: Python SDK - [ ] Component: Java SDK - [ ] Component: Go SDK - [ ] Component: Typescript SDK - [ ] Component: IO connector - [ ] Component: Beam YAML - [ ] Component: Beam examples - [ ] Component: Beam playground - [ ] Component: Beam katas - [ ] Component: Website - [ ] Component: Infrastructure - [ ] Component: Spark Runner - [ ] Component: Flink Runner - [ ] Component: Samza Runner - [ ] Component: Twister2 Runner - [ ] Component: Hazelcast Jet Runner - [ ] Component: Google Cloud Dataflow Runner -- This is an automated message from the Apache Git Service. To respond to the message, please log on to GitHub and use the URL above to go to the specific comment. To unsubscribe, e-mail: [email protected] For queries about this service, please contact Infrastructure at: [email protected]
