Not able to discard new messages when max_msgs_per_subject limit is reached

[rkunnamp]

Observed behavior

The "DiscardNewPerSubject" mentioned here https://docs.nats.io/nats-concepts/jetstream/streams is not supported by python client.

As a result, not able to discard new messages when max_msgs_per_subject limit is reached

import os
import asyncio
import nats
import time


from nats.js.api import  StreamConfig, StreamSource, RetentionPolicy, StorageType, DiscardPolicy



servers = os.environ.get("NATS_URL", "nats://localhost:4222").split(",")



async def run():
    # Connect to NATS server
    nc = await nats.connect(servers=servers)
    
    # Get a JetStream context
    js = nc.jetstream()


    # Stream configuration
    stream_name = "TEST_STREAM"
    subject = "test.subject"

    # Attempt to add stream, or get the stream if it already exists
    try:
        await js.add_stream(name=stream_name, config=StreamConfig(
            retention=RetentionPolicy.LIMITS,
            subjects=[subject], 
            max_msgs_per_subject=5,
            discard=DiscardPolicy.NEW,
        ))
        print(f"Stream {stream_name} created with max_msgs_per_subject=5")
    except Exception as e:
        print(f"Stream {stream_name} already exists. Proceeding with the test.")

    # Publish 10 messages, which should exceed the max_msgs_per_subject limit
    for i in range(10):
        ack = await js.publish(subject, f"Message {i+1}".encode())
        print(f"Published message {i+1}, seq={ack.seq}")

    # Get stream info to check how many messages are retained
    stream_info = await js.stream_info(stream_name)
    print(f"Stream Info: {stream_info.config}")

    # List the messages retained in the stream
    msg = await js.get_last_msg("TEST_STREAM", "test.subject")
    print(f"Last message has the sequence {msg.seq}")



    # Close the NATS connection
    await nc.close()

if __name__ == "__main__":
    asyncio.run(run())

Stream TEST_STREAM created with max_msgs_per_subject=5
Published message 1, seq=1
Published message 2, seq=2
Published message 3, seq=3
Published message 4, seq=4
Published message 5, seq=5
Published message 6, seq=6
Published message 7, seq=7
Published message 8, seq=8
Published message 9, seq=9
Published message 10, seq=10
Stream Info: StreamConfig(name='TEST_STREAM', description=None, subjects=['test.subject'], retention='limits', max_consumers=-1, max_msgs=-1, max_bytes=-1, discard='new', max_age=0.0, max_msgs_per_subject=5, max_msg_size=-1, storage='file', num_replicas=1, no_ack=False, template_owner=None, duplicate_window=120.0, placement=None, mirror=None, sources=None, sealed=False, deny_delete=False, deny_purge=False, allow_rollup_hdrs=False, republish=None, subject_transform=None, allow_direct=False, mirror_direct=False, compression='none', metadata=None)
Last message has the sequence 10

Expected behavior

Ideally there should be a way to discard new messages when max_msgs_per_subject

Server and client version

nats --version
0.1.5

Host environment

No response

Steps to reproduce

No response