Preserve type hints when decoding payload-backed generic Python models - #129
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VegetarianOrc
marked this pull request as ready for review
August 17, 2026 22:52
tconley1428
reviewed
Aug 18, 2026
| type_hint: type[typing.Any], | ||
| ) -> typing.Any: | ||
| proto = value | ||
| (_context_type,) = typing.get_args(type_hint) or (typing.Any,) |
Collaborator
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Maybe don't put _ just in case it isn't used.
tconley1428
reviewed
Aug 18, 2026
| return typing.cast( | ||
| object, | ||
| converter.from_payload(_clone_payload(proto), type_hint), | ||
| ) |
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Check on these casts I think.
tconley1428
reviewed
Aug 18, 2026
| (_output_type,) = typing.get_args(type_hint) or (typing.Any,) | ||
| if not proto.HasField("details"): | ||
| raise ValueError("missing required field PayloadBackedOutput.details") | ||
| details = typing.cast( |
Collaborator
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That's an awful lot of casting.
tconley1428
reviewed
Aug 18, 2026
| ) | ||
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| def payloads_from_proto( |
Collaborator
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Does payloads also need to use the hint?
tconley1428
approved these changes
Aug 18, 2026
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Summary
Payloadfields.typing.Any.Payloadsdecoding as an untyped sequence.Motivation
Proto-backed generic models previously lost their concrete type arguments during nested decoding.
For example, decoding:
could produce dictionaries for payload-backed fields instead of EchoOutput and MyContext instances.
The generated transfer converters now extract runtime generic arguments, propagate them into nested model converters, and provide them to
Temporal’s payload converter.
Unparameterized models continue to decode successfully. They use typing.Any as the fallback instead of object, which Temporal cannot
deserialize as a type hint.
Tests
Validation