#3393 Added support to handle nested Pydantic types Pull request opened by AdilFayyaz ## Tracking issue Duplicated from: flyteorg/flyte-sdk#640 ## Why are the changes needed? To ensure the same behavior persists between v1 and v2 ## What changes were proposed in this pull request? • Fix

_get_element_type()

in the type engine to correctly resolve nested and recursive Pydantic types that were previously flattened to str • Add $ref resolution so nested models or enums inside containers (List, Dict) are resolved via $defs lookup instead of defaulting to str • Rewrite anyOf handling to support $ref variants (e.g. Optional[Inner]), fixing KeyError: 'type' crashes • Add recursive array/object branches so nested containers (List[List[int]], Dict[str, Dict[str, int]]) resolve to their correct Python types • Handle null JSON schema type, returning NoneType instead of str • Add example demonstrating all nested Pydantic type patterns running as parallel Flyte tasks • Note: In v1, _handle_json_schema_property is called recursively for each variant inside an anyOf (e.g. Optional[Inner] produces {"anyOf": [{"$ref": "#/$defs/Inner"}, {"type": "null"}]}). When it recurses on the $ref variant {"$ref": "#/$defs/Inner"}, there is no "type" key, causing a KeyError: 'type'. • v1 iterates over all properties, so we added $ref resolution in

_handle_json_schema_property

before the "type" lookup to delegate to

_get_element_type

, which already knows how to resolve $ref paths. ## How was this patch tested? • pytest tests/flytekit/unit/core/test_nested_structs_in_pydantic.py: 16 new tests covering - • Nested arrays: List[List[int]] schema resolution + roundtrip, List[List[Inner]] roundtrip • Nested dicts: List[Dict[str, int]] schema + roundtrip, Dict[str, Dict[str, int]] schema + roundtrip, List[Dict[str, Inner]] roundtrip, Dict[str, Dict[str, Inner]] roundtrip • anyOf with $ref: List[Optional[Inner]] schema resolution (no KeyError), List[Optional[str]] schema resolution, List[Optional[Inner]] roundtrip via guess_python_type • null type: {"type": "null"} resolves to NoneType • Enums in containers: List[ModelWithEnum] roundtrip, Dict[str, ModelWithEnum] roundtrip • Complex combined: model with List[List[Inner]], Dict[str, Inner], List[Dict[str, int]], List[ModelWithEnum], Optional[Inner] roundtrip with data and with None optional ### Setup process ### Screenshots ## Check all the applicable boxes • I updated the documentation accordingly. • All new and existing tests passed. • All commits are signed-off. ## Related PRs ## Docs link flyteorg/flytekit