fix(idempotency): serialize Pydantic models with mode='json' for UUID/date support

The `_prepare_data()` function was calling `model_dump()` without specifying
`mode="json"`, which defaults to `mode="python"`. This caused Pydantic models
containing UUIDs, dates, or datetimes to fail with "Object of type UUID is not
JSON serializable" when used with `@idempotent_function`.

Fixes #8065

Author: abhu85

aws_lambda_powertools/utilities/idempotency/base.py

@@ -60,7 +60,7 @@ def _prepare_data(data: Any) -> Any:
 
     # Convert from Pydantic model
     if callable(getattr(data, "model_dump", None)):
-        return data.model_dump()
+        return data.model_dump(mode="json")
 
     # Convert from event source data class
     if callable(getattr(data, "dict", None)):

tests/functional/idempotency/_pydantic/test_idempotency_uuid_serialization.py

@@ -0,0 +1,157 @@
+"""
+Test for issue #8065: @idempotent_function fails with UUID in Pydantic model
+
+Bug: _prepare_data() calls model_dump() without mode="json", which doesn't
+serialize UUIDs and dates to JSON-compatible strings.
+"""
+
+from datetime import date, datetime
+from uuid import UUID, uuid4
+
+import pytest
+from pydantic import BaseModel
+
+from aws_lambda_powertools.utilities.idempotency import (
+    IdempotencyConfig,
+    idempotent_function,
+)
+from aws_lambda_powertools.utilities.idempotency.base import _prepare_data
+from aws_lambda_powertools.utilities.idempotency.persistence.base import (
+    BasePersistenceLayer,
+    DataRecord,
+)
+from tests.functional.idempotency.utils import hash_idempotency_key
+
+
+TESTS_MODULE_PREFIX = "test-func.tests.functional.idempotency._pydantic.test_idempotency_uuid_serialization"
+
+
+class MockPersistenceLayer(BasePersistenceLayer):
+    """Mock persistence layer that tracks idempotency key assertions."""
+
+    def __init__(self, expected_idempotency_key: str):
+        self.expected_idempotency_key = expected_idempotency_key
+        super().__init__()
+
+    def _put_record(self, data_record: DataRecord) -> None:
+        assert data_record.idempotency_key == self.expected_idempotency_key
+
+    def _update_record(self, data_record: DataRecord) -> None:
+        assert data_record.idempotency_key == self.expected_idempotency_key
+
+    def _get_record(self, idempotency_key) -> DataRecord:
+        ...
+
+    def _delete_record(self, data_record: DataRecord) -> None:
+        ...
+
+
+class PaymentWithUUID(BaseModel):
+    """Pydantic model with UUID field - reproduces issue #8065."""
+
+    payment_id: UUID
+    customer_id: str
+
+
+class EventWithDate(BaseModel):
+    """Pydantic model with date field."""
+
+    event_id: str
+    event_date: date
+
+
+class OrderWithDatetime(BaseModel):
+    """Pydantic model with datetime field."""
+
+    order_id: str
+    created_at: datetime
+
+
+def test_prepare_data_pydantic_with_uuid():
+    """
+    Test that _prepare_data correctly serializes Pydantic models with UUID fields.
+
+    Issue #8065: model_dump() without mode="json" returns UUID objects instead of strings,
+    which causes "Object of type UUID is not JSON serializable" error.
+    """
+    # GIVEN a Pydantic model with UUID
+    payment_uuid = uuid4()
+    payment = PaymentWithUUID(payment_id=payment_uuid, customer_id="customer-123")
+
+    # WHEN preparing data for idempotency
+    result = _prepare_data(payment)
+
+    # THEN UUID should be serialized as string (not UUID object)
+    assert isinstance(result, dict)
+    assert isinstance(result["payment_id"], str), (
+        f"UUID should be serialized as string, got {type(result['payment_id'])}"
+    )
+    assert result["payment_id"] == str(payment_uuid)
+    assert result["customer_id"] == "customer-123"
+
+
+def test_prepare_data_pydantic_with_date():
+    """Test that _prepare_data correctly serializes Pydantic models with date fields."""
+    # GIVEN a Pydantic model with date
+    event_date = date(2024, 1, 15)
+    event = EventWithDate(event_id="event-123", event_date=event_date)
+
+    # WHEN preparing data for idempotency
+    result = _prepare_data(event)
+
+    # THEN date should be serialized as ISO format string
+    assert isinstance(result, dict)
+    assert isinstance(result["event_date"], str), (
+        f"date should be serialized as string, got {type(result['event_date'])}"
+    )
+    assert result["event_date"] == "2024-01-15"
+
+
+def test_prepare_data_pydantic_with_datetime():
+    """Test that _prepare_data correctly serializes Pydantic models with datetime fields."""
+    # GIVEN a Pydantic model with datetime
+    created_at = datetime(2024, 1, 15, 10, 30, 0)
+    order = OrderWithDatetime(order_id="order-123", created_at=created_at)
+
+    # WHEN preparing data for idempotency
+    result = _prepare_data(order)
+
+    # THEN datetime should be serialized as ISO format string
+    assert isinstance(result, dict)
+    assert isinstance(result["created_at"], str), (
+        f"datetime should be serialized as string, got {type(result['created_at'])}"
+    )
+
+
+def test_idempotent_function_with_uuid_in_pydantic_model():
+    """
+    Integration test for idempotent_function with UUID in Pydantic model.
+
+    This is the main test case for issue #8065.
+    """
+    # GIVEN
+    config = IdempotencyConfig(use_local_cache=True)
+    payment_uuid = UUID("12345678-1234-5678-1234-567812345678")
+    mock_event = {"payment_id": str(payment_uuid), "customer_id": "customer-456"}
+
+    idempotency_key = (
+        f"{TESTS_MODULE_PREFIX}.test_idempotent_function_with_uuid_in_pydantic_model"
+        f".<locals>.process_payment#{hash_idempotency_key(mock_event)}"
+    )
+    persistence_layer = MockPersistenceLayer(expected_idempotency_key=idempotency_key)
+
+    @idempotent_function(
+        data_keyword_argument="payment",
+        persistence_store=persistence_layer,
+        config=config,
+    )
+    def process_payment(payment: PaymentWithUUID) -> dict:
+        return {"status": "processed", "payment_id": str(payment.payment_id)}
+
+    # WHEN processing payment with UUID
+    payment = PaymentWithUUID(payment_id=payment_uuid, customer_id="customer-456")
+
+    # THEN it should not raise "Object of type UUID is not JSON serializable"
+    result = process_payment(payment=payment)
+    assert result["status"] == "processed"
+    assert result["payment_id"] == str(payment_uuid)