[MCC-1532869] Python Lib-Details section is missing for error message if first_n_rows parameter is not parsed

dataconnect/service/default.py

@@ -8,7 +8,7 @@
 
 import pandas as pd
 
-from dataconnect.exceptions import ValidationError
+from dataconnect.exceptions import ErrorDetail, ValidationError
 from dataconnect.models import (
     Dataset,
     DatasetVersion,
@@ -49,6 +49,27 @@
 _VALID_DATETIME_FORMAT_TYPES: frozenset[str] = frozenset({"all", "date", "datetime"})
 
 
+def _coerce_int_field(field: str, field_value: int | None) -> int | None:
+    if field_value is None:
+        return None
+
+    try:
+        return int(field_value)
+    except (ValueError, TypeError) as ex:
+        message = str(ex) if isinstance(ex, ValueError) else f"invalid literal for int() with base 10: {field_value}"
+        raise ValidationError(
+            error_code="INT_001",
+            message=message,
+            timestamp=datetime.now(UTC).strftime("%Y-%m-%dT%H:%M:%SZ"),
+            details=[
+                ErrorDetail(
+                    field=field,
+                    expected="Ensure you provide a numeric value for this field.",
+                )
+            ],
+        ) from ex
+
+
 class DefaultDataConnectService(DataConnectService):
     """Concrete service injected with an abstract ``Transport``."""
 
@@ -112,7 +133,7 @@ def fetch_data(self, dataset_uuid: UUID, first_n_rows: int | None = None) -> pd.
 
         ticket = DatasetTicket(
             dataset_uuid=str(dataset_uuid),
-            limit=first_n_rows,
+            limit=_coerce_int_field("first_n_rows", first_n_rows),
         )
 
         try:

tests/test_fetch_data.py

@@ -13,6 +13,7 @@
     AuthorizationError,
     NotFoundError,
     ServerError,
+    ValidationError,
 )
 from dataconnect.service.default import DefaultDataConnectService
 from dataconnect.transport.errors import (
@@ -107,6 +108,38 @@ def test_fetch_data_no_limit_sends_none_in_ticket() -> None:
     assert transport.last_ticket.limit is None
 
 
+def test_fetch_data_raises_formatted_validation_error_for_non_numeric_first_n_rows() -> None:
+    dataset_uuid = UUID("073410b6-79be-3e7d-ae37-92f6e054013e")
+    transport = _FakeTransport(data_table=_make_ipc_table({"x": [1]}))
+    service = DefaultDataConnectService(transport)
+
+    with pytest.raises(ValidationError) as exc_info:
+        service.fetch_data(dataset_uuid, first_n_rows="ten")  # type: ignore[arg-type]
+
+    error = str(exc_info.value)
+    assert "Error Code: [INT_001]" in error
+    assert "Message: invalid literal for int() with base 10: 'ten'" in error
+    assert "Field: first_n_rows" in error
+    assert "Expected: Ensure you provide a numeric value for this field." in error
+    assert transport.last_ticket is None
+
+
+def test_fetch_data_raises_formatted_validation_error_for_dict_first_n_rows() -> None:
+    dataset_uuid = UUID("073410b6-79be-3e7d-ae37-92f6e054013e")
+    transport = _FakeTransport(data_table=_make_ipc_table({"x": [1]}))
+    service = DefaultDataConnectService(transport)
+
+    with pytest.raises(ValidationError) as exc_info:
+        service.fetch_data(dataset_uuid, first_n_rows={})  # type: ignore[arg-type]
+
+    error = str(exc_info.value)
+    assert "Error Code: [INT_001]" in error
+    assert "Message: invalid literal for int() with base 10: {}" in error
+    assert "Field: first_n_rows" in error
+    assert "Expected: Ensure you provide a numeric value for this field." in error
+    assert transport.last_ticket is None
+
+
 def test_fetch_data_returns_empty_dataframe_for_empty_table() -> None:
     dataset_uuid = UUID("073410b6-79be-3e7d-ae37-92f6e054013e")
     transport = _FakeTransport(data_table=_make_ipc_table({"col": pa.array([], type=pa.int32())}))