Allow tagged types in with_exception_handling.

[claudevdm]

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Summary of Changes

Hello @claudevdm, I'm Gemini Code Assist¹! I'm currently reviewing this pull request and will post my feedback shortly. In the meantime, here's a summary to help you and other reviewers quickly get up to speed!

This pull request addresses a limitation in Apache Beam's exception handling mechanism where type hints for tagged outputs were not correctly propagated. The changes ensure that when with_exception_handling is applied to a ParDo that produces tagged outputs, the resulting PCollections retain their inferred or explicitly provided type information. This improves the robustness and type safety of pipelines that combine these features, while also providing backward compatibility for older deployments.

Highlights

• Enhanced Type Hint Propagation: The with_exception_handling transform now correctly propagates type hints for both main and tagged outputs, ensuring that PCollection types are preserved when using with_outputs in conjunction with exception handling.
• Refactored Exception Handling Logic: The internal _ExceptionHandlingWrapper has been refactored to explicitly manage and apply type hints to its outputs, utilizing with_output_types for better type inference.
• Backward Compatibility: A compatibility check has been introduced to maintain the previous behavior for pipelines running on Beam versions prior to 2.72.0, preventing breaking changes for existing users.
• New Test Cases: Comprehensive unit tests have been added to validate the correct interaction between with_exception_handling and with_outputs in various configurations, including custom dead letter tags and different chaining orders.

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Changelog

• sdks/python/apache_beam/transforms/core.py
  • Modified ParDo.with_exception_handling to pass type hints to the exception handling wrapper.
  • Added a new with_exception_handling method to _NamedPTransform to correctly manage and propagate output tags.
  • Updated _ExceptionHandlingWrapper.__init__ to accept pardo_type_hints and store _extra_tags.
  • Introduced with_outputs method in _ExceptionHandlingWrapper to handle output tag configuration.
  • Refactored the _ExceptionHandlingWrapper.expand method into _build_pardo and _post_process_result for clarity and modularity.
  • Implemented logic within _ExceptionHandlingWrapper.expand to apply type hints to main and tagged outputs using with_output_types.
  • Added a version compatibility check (is_compat_version_prior_to("2.72.0")) to preserve the old expand behavior for older pipelines.
• sdks/python/apache_beam/transforms/core_test.py
  • Added new imports for Iterable, Literal, and PipelineOptions.
  • Introduced ExceptionHandlingWithOutputsTest class to test the integration of with_exception_handling and with_outputs.
  • Included test cases for chaining with_exception_handling before and after with_outputs.
  • Added tests to verify correct type hint propagation for main, tagged, and dead letter outputs.
  • Created tests for custom dead letter tags and their impact on type inference.
  • Implemented tests to confirm backward compatibility for pipelines running on Beam versions prior to 2.72.0.
  • Added test cases for Map transforms and ParDo with chained with_output_types to ensure consistent behavior.

Activity

• No specific human activity (comments, reviews, or progress updates) has been recorded for this pull request beyond its initial creation.

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