`js.get_msg(..., direct=True)` does not populate `RawStreamMsg.time`

[oliverlambson]

Proposed change

Parse "Nats-Time-Stamp" header into RawStreamMsg.time

In js.get_msg(..., direct=False), time is populated by RawStreamMsg.from_response(), but from_response() isn't used for direct get because the time is in response.headers["Nats-Time-Stamp"] instead of the response["time"]

A way to do this would be:

• pull the RawStreamMsg._python38_iso_parsing classmethod out into a helper function
• use that helper function in JetstreamManager._lift_msg_to_raw_msg:

  @classmethod
  def _lift_msg_to_raw_msg(self, msg) -> api.RawStreamMsg:
      ...
      seq = msg.headers.get("Nats-Sequence")
      if seq:
          raw_msg.seq = int(seq)
      raw_msg.data = msg.data
      raw_msg.headers = msg.headers
+     if time_string := msg.headers.get("Nats-Time-Stamp"):
+         raw_msg.time = parse_iso_dt(time_string)

      return raw_msg

Use case

Anyone who wants to use the message timestamp from a direct get currently has to parse it out manually, which is unexpected behaviour and not a great experience:

from datetime import UTC, datetime

nc = nats.connect()
js = nc.jetstream()
msg = await js.get_msg(..., direct=True)
if msg.time is None and msg.headers and (dt := msg.headers.get("Nats-Time-Stamp")):
    msg.time = datetime.fromisoformat(dt).astimezone(UTC)

# parsing above requires python 3.11+
# for <3.11 need to drop ns from dt string first and use datetime.timezone.utc

Contribution

Sure

[nguyenvantam00]

you need to separate the logic for parsing the ios datetime into a helper, and here is how to handle this in python version <3.11, z = +00:00, nanoseconds = microseconds.
with if (dt := msg.headers.get("nats-stamp")):
raw_msg.time = parse_iso_dt(dt)
so when direct=True, msg.time will behave exactly the same as direct=false