Support datetime.date in encode_value auto-inference

datetime.date objects now encode as ISO8601 text using isoformat().
Previously they raised EncodeError("Cannot infer type"), which was
surprising since datetime.datetime was already supported.

Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>

Author: antoineleclair

src/dqlitewire/types.py

@@ -181,6 +181,10 @@ def encode_value(value: Any, value_type: ValueType | None = None) -> tuple[bytes
                 # Naive datetime: assume UTC to match Go's always-offset format
                 formatted += "+00:00"
             value = formatted
+        elif isinstance(value, datetime.date):
+            # Must come after datetime.datetime check (datetime is a subclass of date)
+            value_type = ValueType.ISO8601
+            value = value.isoformat()
         elif isinstance(value, str):
             value_type = ValueType.TEXT
         elif isinstance(value, bytes):

tests/test_types.py

@@ -329,6 +329,18 @@ def test_boolean_explicit_rejects_non_bool_non_int(self) -> None:
         with pytest.raises(EncodeError, match="[Bb]ool"):
             encode_value({"key": "val"}, ValueType.BOOLEAN)
 
+    def test_encode_date_as_iso8601(self) -> None:
+        """datetime.date should encode as ISO8601 text."""
+        import datetime
+
+        encoded, vtype = encode_value(datetime.date(2024, 1, 15))
+        assert vtype == ValueType.ISO8601
+        decoded, _ = decode_value(encoded, ValueType.ISO8601)
+        assert isinstance(decoded, datetime.datetime)
+        assert decoded.year == 2024
+        assert decoded.month == 1
+        assert decoded.day == 15
+
     def test_decode_integer(self) -> None:
         value, consumed = decode_value(encode_int64(42), ValueType.INTEGER)
         assert value == 42