Add a new converter to the default DataConverter for datetimes

Author: tconley1428

temporalio/converter.py

@@ -485,6 +485,35 @@ def from_payload(
             raise RuntimeError("Failed parsing") from err
 
 
+class ISO8601DatetimePayloadConverter(EncodingPayloadConverter):
+    """Converter for 'binary/iso8601' payloads supporting datetime values."""
+
+    @property
+    def encoding(self) -> str:
+        """See base class."""
+        return "binary/iso8601"
+
+    def to_payload(self, value: Any) -> Optional[temporalio.api.common.v1.Payload]:
+        """See base class."""
+        if isinstance(value, datetime):
+            return temporalio.api.common.v1.Payload(
+                metadata={"encoding": self.encoding.encode()},
+                data=value.isoformat().encode(),
+            )
+        return None
+
+    def from_payload(
+        self,
+        payload: temporalio.api.common.v1.Payload,
+        type_hint: Optional[Type] = None,
+    ) -> Any:
+        """See base class."""
+        try:
+            return datetime.fromisoformat(payload.data.decode())
+        except ValueError as err:
+            raise RuntimeError("Failed parsing ISO8601 datetime") from err
+
+
 class AdvancedJSONEncoder(json.JSONEncoder):
     """Advanced JSON encoder.
 
@@ -1132,7 +1161,8 @@ async def decode_failure(
     BinaryPlainPayloadConverter(),
     JSONProtoPayloadConverter(),
     BinaryProtoPayloadConverter(),
-    JSONPlainPayloadConverter(),
+    ISO8601DatetimePayloadConverter(),
+    JSONPlainPayloadConverter(),  # JSON Plain needs to remain in last because it throws on unknown types
 )
 
 DataConverter.default = DataConverter()

tests/test_converter.py

@@ -178,6 +178,13 @@ async def assert_payload(
         type_hint=RawValue,
     )
 
+    await assert_payload(
+        datetime(2020, 1, 1, 1, 1, 1), "binary/iso8601", "2020-01-01T01:01:01"
+    )
+    await assert_payload(
+        datetime(2020, 1, 1, 1, 1, 1, 1), "binary/iso8601", "2020-01-01T01:01:01.000001"
+    )
+
 
 def test_binary_proto():
     # We have to test this separately because by default it never encodes