Flaky test fix

docs/types.md

@@ -76,6 +76,13 @@ protarrow.ProtarrowConfig(
 )
 ```
 
+## Date range limitation
+
+`google.type.Date` is converted through Python's `datetime.date`, which only supports dates from
+`0001-01-01` to `9999-12-31`. Proto `Date` values outside this range (e.g. `Date(year=0, month=0, day=0)`)
+cannot be represented as `datetime.date`. These values are stored using a special sentinel value and
+will round-trip back as `Date(year=0, month=0, day=0)` regardless of the original month and day.
+
 ## Nullability
 
 By default, nullability follows the convention imposed by protobuf:

protarrow/arrow_to_proto.py

@@ -23,7 +23,13 @@
 from google.type.date_pb2 import Date
 from google.type.timeofday_pb2 import TimeOfDay
 
-from protarrow.common import M, is_binary_enum, is_string_enum, offset_values_array
+from protarrow.common import (
+    _INVALID_DATE_SENTINEL,
+    M,
+    is_binary_enum,
+    is_string_enum,
+    offset_values_array,
+)
 
 _NANOS_PER_UNIT = {"ns": 1, "us": 1_000, "ms": 1_000_000, "s": 1_000_000_000}
 _TIME_CONVERTER = {
@@ -59,11 +65,10 @@ def _timestamp_s_scalar_to_proto(scalar: pa.TimestampScalar) -> Timestamp:
 
 
 def _date_scalar_to_proto(scalar: pa.Date32Scalar) -> Date:
-    date: datetime.date = scalar.as_py()
-    if date == datetime.date.min:
+    if scalar.value == _INVALID_DATE_SENTINEL:
         return Date()
-    else:
-        return Date(year=date.year, month=date.month, day=date.day)
+    date: datetime.date = scalar.as_py()
+    return Date(year=date.year, month=date.month, day=date.day)
 
 
 def _time_64_ns_scalar_to_proto(scalar: pa.Time64Scalar) -> TimeOfDay:

protarrow/common.py

@@ -6,6 +6,8 @@
 
 M = TypeVar("M", bound=Message)
 
+_INVALID_DATE_SENTINEL = -719163
+
 SUPPORTED_ENUM_TYPES = (
     pa.int32(),
     pa.binary(),

protarrow/proto_to_arrow.py

@@ -37,7 +37,13 @@
 from google.type.date_pb2 import Date
 from google.type.timeofday_pb2 import TimeOfDay
 
-from protarrow.common import M, ProtarrowConfig, is_binary_enum, is_string_enum
+from protarrow.common import (
+    _INVALID_DATE_SENTINEL,
+    M,
+    ProtarrowConfig,
+    is_binary_enum,
+    is_string_enum,
+)
 
 _PROTO_DESCRIPTOR_TO_PYARROW = {
     BoolValue.DESCRIPTOR: pa.bool_(),
@@ -89,15 +95,16 @@ def _time_of_day_to_seconds(time_of_day: TimeOfDay) -> int:
     return (time_of_day.hours * 60 + time_of_day.minutes) * 60 + time_of_day.seconds
 
 
-def _proto_date_to_py_date(proto_date: Date) -> datetime.date:
+def _proto_date_to_date32(proto_date: Date) -> int:
     if proto_date.year == 0:
-        return datetime.date.min
+        return _INVALID_DATE_SENTINEL
     else:
-        return datetime.date(proto_date.year, proto_date.month, proto_date.day)
+        date = datetime.date(proto_date.year, proto_date.month, proto_date.day)
+        return date.toordinal() + _INVALID_DATE_SENTINEL
 
 
 _PROTO_DESCRIPTOR_TO_ARROW_CONVERTER = {
-    Date.DESCRIPTOR: _proto_date_to_py_date,
+    Date.DESCRIPTOR: _proto_date_to_date32,
     TimeOfDay.DESCRIPTOR: _time_of_day_to_nanos,
     BoolValue.DESCRIPTOR: operator.attrgetter("value"),
     BytesValue.DESCRIPTOR: operator.attrgetter("value"),

tests/random_generator.py

@@ -42,7 +42,7 @@ def random_duration() -> Duration:
 
 
 def random_date() -> Date:
-    date = datetime.date.min + datetime.timedelta(days=random.randint(0, 3652058))
+    date = datetime.date.fromordinal(random.randint(1, 3652059))
     return Date(year=date.year, month=date.month, day=date.day)
 
 

tests/test_coverage.py

@@ -11,6 +11,7 @@
 import pytest
 from google.protobuf.descriptor import Descriptor, EnumDescriptor, FieldDescriptor
 from google.protobuf.wrappers_pb2 import BoolValue, DoubleValue
+from google.type.date_pb2 import Date
 
 import protarrow
 from protarrow import cast_record_batch
@@ -575,3 +576,59 @@ def test_dict_binary_enum_with_large_binary(self):
             binary_type=pa.large_binary(),
         )
         assert config.enum_type == pa.dictionary(pa.int32(), pa.binary())
+
+
+def test_date_behavior():
+    assert pa.scalar(0, pa.date32()).as_py() == datetime.date(1970, 1, 1)
+    assert pa.scalar(-1, pa.date32()).as_py() == datetime.date(1969, 12, 31)
+    assert pa.scalar(-719162, pa.date32()).as_py() == datetime.date(1, 1, 1)
+    with pytest.raises(OverflowError, match=r"date value out of range"):
+        assert pa.scalar(-719163, pa.date32()).as_py()
+
+    assert datetime.date(1970, 1, 1).toordinal() == 719163
+    assert datetime.date.min.toordinal() == 1
+    assert datetime.date.max.toordinal() == 3652059
+
+    assert datetime.date.fromordinal(1) == datetime.date.min
+    assert datetime.date.fromordinal(3652059) == datetime.date.max
+
+
+def test_bad_date():
+    default_date = Date()
+    min_date = Date(year=1, month=1, day=1)
+
+    assert default_date != min_date
+
+
+def test_can_pass_min_max_date():
+    default_date = Date()
+    bad_date = Date(year=0, month=1, day=1)
+    min_date = Date(year=1, month=1, day=1)
+    max_date = Date(year=9999, month=12, day=31)
+
+    messages = [
+        ExampleMessage(date_value=default_date),
+        ExampleMessage(date_value=bad_date),
+        ExampleMessage(date_value=min_date),
+        ExampleMessage(date_value=max_date),
+    ]
+    table = protarrow.messages_to_table(messages, ExampleMessage)
+    assert table["date_value"] == pa.chunked_array(
+        pa.array(
+            [
+                -719163,
+                -719163,
+                -719162,
+                2932896,
+            ],
+            type=pa.date32(),
+        )
+    )
+
+    messages_back = protarrow.table_to_messages(table, ExampleMessage)
+    assert messages_back == [
+        ExampleMessage(date_value=default_date),
+        ExampleMessage(date_value=default_date),  # This changed
+        ExampleMessage(date_value=min_date),
+        ExampleMessage(date_value=max_date),
+    ]