Sample

Exclude default values in Pydantic models nested in dict keys and values when serializing with jsonable_encoder as fixed in FastAPI 0.140.9

sha256:b09b062b12f13c860852641882840dceca140b65e173f95222f347f4f95b25b6

PUBLISHED L3_CONTRACT_PASS MIT-0

Case

Goal: Exclude default values in Pydantic models nested in dict keys and values when serializing with jsonable_encoder as fixed in FastAPI 0.140.9 HOW
Packages: fastapi 0.141.1 pydantic 2.13.4 starlette 1.6.0 httpx 0.28.1
Environment: python
Created: 2026-08-16T06:22:41Z

assert TestClient targets http://testserver, so the contract runs with network off and no DNS sockets
assert jsonable_encoder([item], exclude_defaults=True) excludes default fields from items in top-level lists
assert jsonable_encoder({'item': item}, exclude_defaults=True) propagates exclude_defaults into dict values instead of leaking default fields
assert jsonable_encoder({'items': [item]}, exclude_defaults=True) propagates exclude_defaults through dicts containing lists
assert jsonable_encoder({'data': {'items': [item]}}, exclude_defaults=True) propagates exclude_defaults through deeply nested dicts
assert jsonable_encoder preserves default fields when exclude_defaults is False or omitted
assert jsonable_encoder preserves non-default overridden fields when exclude_defaults is True
assert exclude_defaults=True strips fields explicitly assigned their default value whereas exclude_unset=True retains them
assert jsonable_encoder excludes defaults from nested Pydantic container models inside dictionaries
assert jsonable_encoder({'data': null_model}, exclude_none=True) excludes None fields consistently
assert FastAPI route responses returning dicts with exclude_defaults=True omit default fields over the wire

python 3.12 · CONTAINER_RUN · compile:SKIPPED · contract:PASS · load:PASS · resolve:PASS · python@1 · 2026-08-16 · ed25519:d91480838ac982c9