#3339 Bugfix: Pydantic deserialization for FlyteFile and FlyteDirectory Pull request opened by gverkes Fixes #6669 ## Tracking issue Closes flyteorg/flyte#6669 ## Why are the changes needed? When deserializing Pydantic models containing

FlyteFile

or

FlyteDirectory

fields using

model_validate()

, the deserialized objects were missing private attributes (

_remote_source

,

_downloader

, etc.). This caused an

AttributeError

when attempting to re-serialize these objects with

model_dump()

, breaking the serialize → deserialize → serialize cycle. This is a critical bug that prevents users from using FlyteFile/FlyteDirectory within Pydantic BaseModel classes in a normal way. ## What changes were proposed in this pull request? Added Pydantic model validators to both

FlyteFile

and

FlyteDirectory

classes that ensure private attributes are properly initialized during deserialization: 1. FlyteFile (

flytekit/types/file/file.py

): • Enhanced

deserialize_flyte_file

validator to check if private attributes exist • If missing, reconstructs the FlyteFile using

dict_to_flyte_file()

transformer • If attributes already exist (e.g., when passing already-constructed FlyteFile), returns as-is 2. FlyteDirectory (

flytekit/types/directory/types.py

): • Applied same fix to

deserialize_flyte_dir

validator • Uses

dict_to_flyte_directory()

to properly reconstruct the object ## How was this patch tested? Added two new unit tests in `test_pydantic_basemodel_transformer.py`: 1.

test_flytefile_pydantic_model_dump_validate_cycle

- Verifies FlyteFile can be serialized, deserialized, and re-serialized without errors 2.

test_flytedirectory_pydantic_model_dump_validate_cycle

- Same for FlyteDirectory ## Check all the applicable boxes • I updated the documentation accordingly. • All new and existing tests passed. • All commits are signed-off. https://bito.ai#summarystart| ### Summary by Bito • This pull request introduces a critical bug in the deserialization of Pydantic models containing FlyteFile and FlyteDirectory fields, which could lead to AttributeErrors during re-serialization. • Model validators are added to ensure that private attributes are properly initialized during deserialization. • New unit tests have been added to verify the functionality of these changes, ensuring that the serialize-deserialize-serialize cycle works without errors. • Overall, this pull request addresses deserialization issues in Pydantic models, introduces critical bugs, and adds unit tests. flyteorg/flytekit