Handle some cases during infer schema from dataclass

[Abacn]

After #37728 added support for inferring schema from dataclasses

If dataclass is inherited, the subclass assumes Beam Schema ID from base class, which isn't correct. Also, the change exposed another issue (previously could also happen for named tuple) for user types defined __iter__ but does not have a typehint for element type.

This change

• Make sure Beam schema ID does not inherit

• Fix IndexOutofBoundError trying to infer type from custom Iterable without type hint

internal tracker b/492300593

Please add a meaningful description for your change here

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Summary of Changes

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This pull request enhances the robustness and correctness of schema inference within Apache Beam's type hinting system. It specifically refines how schemas are generated for dataclasses by preventing unintended inheritance of schema IDs from base classes, thereby ensuring type-specific schema generation. Additionally, it introduces a defensive check during type inference for generic collections like Iterable and Sequence to prevent errors when type arguments are missing, improving the stability of the schema generation process.

Highlights

• Beam Schema ID Inheritance: Implemented logic to prevent _BEAM_SCHEMA_ID from inheriting from base classes when inferring schemas for derived dataclasses, ensuring each type has a unique and correct schema identifier.
• IndexOutOfBoundsError Fix: Addressed a potential IndexOutOfBoundsError when inferring types from custom Iterable or Sequence types that might not have explicit type hints, by safely checking for the presence of type arguments.

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Changelog

• sdks/python/apache_beam/typehints/row_type.py
  • Modified RowTypeConstraint initialization to unset _schema_id if it was inherited from a base class, ensuring it's only set if explicitly defined on the current type.
• sdks/python/apache_beam/typehints/row_type_test.py
  • Added a new test case test_derived_dataclass_schema_id to verify that _BEAM_SCHEMA_ID is not inherited by derived dataclasses.
  • Imported the schemas module for use in the new test.
• sdks/python/apache_beam/typehints/schemas.py
  • Updated typing_to_runner_api to check the length of _get_args(type_) before accessing its elements for Sequence and Iterable types, preventing IndexOutOfBoundsError.
  • Changed the condition for checking _BEAM_SCHEMA_ID in schema_from_element_type from hasattr to _BEAM_SCHEMA_ID in element_type.__dict__ to explicitly prevent inheritance from base classes.

Activity

• Abacn created this pull request to address issues with schema inference from dataclasses.
• The pull request description outlines two main objectives: preventing Beam schema ID inheritance and fixing an IndexOutOfBoundsError.

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