#630 fix: Handle list[Model], dict[str, Model] and Optional[Model] in nested type detection Pull request opened by andreahlert ## Motivation PR #426 added support for nested Pydantic/dataclass schema detection via

$ref

, but as noted in flyteorg/flyte#6887 (item 1), it does not handle

list

and

map

containers with nested models. When a schema contains

list[NestedModel]

,

dict[str, NestedModel]

, or

Optional[NestedModel]

, the

$ref

inside

items

,

additionalProperties

, or

anyOf

was not resolved, causing

KeyError

or incorrect type inference (falling back to

str

). ## Changes ### Centralized

$ref

resolution Instead of inlining

$ref

resolution at every call site, this PR follows the same approach as flytekit PR #3375:

_get_element_type

now accepts an optional

schema

parameter and resolves

$ref

centrally. This means any container type (

list

,

dict

,

Optional

, or nested combinations) automatically gets

$ref

support. ### New helper functions •

_resolve_ref

: Centralized

$ref

path resolution to schema definition •

_resolve_property_type

: Resolves a JSON schema property to a

(name, type)

tuple, handling

$ref

,

anyOf

, and all type variants •

_resolve_single_type

: Resolves the inner type of

Optional[T]

from the first

anyOf

element, properly handling

$ref

,

array

,

object

, and primitive types •

_resolve_typed_property

: Resolves a property with a known type string (array, object, primitives) •

_is_optional_anyof

: Validates that an

anyOf

truly represents

Optional[T]

(exactly 2 elements, second is

null

) instead of blindly assuming any

anyOf

with

$ref

is Optional ### Bug fixes •

Optional[T]

default values: Fields not in the schema's

required

list now get

default=None

in the generated dataclass, so constructing with omitted optional fields works correctly •

Optional[List[Model]]

/

Optional[Dict[str, Model]]

: Previously would crash with

KeyError

because the code accessed

property_val["items"]

instead of

anyOf[0]["items"]

- now handled correctly via

_resolve_single_type

•

Union[TypeA, TypeB]

: Previously any

anyOf

with

$ref

was blindly wrapped in

Optional

- now properly validated • Optional field inclusion: Properties not in

required

are included in

property_order

so fields with defaults (like

Optional[X] = None

) are not skipped during schema traversal ###

__init__

wrapper Extended dict-to-object conversion to handle

list[dict]

->

list[Model]

and

dict[str, dict]

->

dict[str, Model]

. ## Tests Added

test_nested_lists_maps.py

with 10 test cases covering: •

list[NestedModel]

roundtrip (Pydantic + dataclass) •

dict[str, NestedModel]

roundtrip (Pydantic + dataclass) •

Optional[NestedModel]

with value and with

None

•

Optional[NestedModel]

omitted (default to

None

) • Mixed initialization (dict + object in same list) • Empty collections (

[]

,

{}

) All existing type engine tests pass with zero regressions. Ref: flyteorg/flyte#6887 flyteorg/flyte-sdk