Request: `list_sessions` to return an empty list if 'no server running on ...'

[xlucn]

The problem is that I can't find a method to check if there is any sessions running, or tmux server running (for the current socket), without catching a LibTmuxException exception. It will be convenient to check that by telling whether the list is empty or not.

Same goes for sessions and attached_sessions attributes.

It is strange/unexpected to get an exception from common tasks like accessing an attribute or requiring a list of something.

Or, a more direct solution is to add a function to check the availability of the server.

[tony]

@oliverlew This issue has come up before

cc: @rockandska

Any thoughts on a default error, or better behavior when no server connection exists?

I am +1 on having sessions and attached_sessions be empty, e.g. [] if no server exists, and then perhaps have an .alive or .connected property, or .is_connected()

Any other ideas?

We also want to make sure we don't break any APIs for existing users

[tony]

It is strange/unexpected to get an exception from common tasks like accessing an attribute or requiring a list of something.

The thinking was that libtmux is a client, and would behave like tmux(1), or like any other client interface would

redis-cli  --bigkeys
Could not connect to Redis at 127.0.0.1:6379: Connection refused

~ ❯ python
Python 3.10.7 (main, Sep 18 2022, 17:05:16) [GCC 11.2.0] on linux
Type "help", "copyright", "credits" or "license" for more information.
ptpython is not available: falling back to standard prompt
>>> import redis
>>>
>>> r = redis.StrictRedis(host='localhost', port=6379, db=0)
... print(r.execute_command('INFO')['redis_version'])

python -c "import redis; print(redis.StrictRedis(host='localhost', port=6379, db=0).execute_command('INFO')['redis_version'])"
Traceback (most recent call last):
  File "python3.10/site-packages/redis/connection.py", line 611, in connect
    sock = self.retry.call_with_retry(
  File "python3.10/site-packages/redis/retry.py", line 46, in call_with_retry
    return do()
  File "python3.10/site-packages/redis/connection.py", line 612, in <lambda>
    lambda: self._connect(), lambda error: self.disconnect(error)
  File "/home/t/.local/lib/python3.10/site-packages/redis/connection.py", line 677, in _connect
    raise err
  File "python3.10/site-packages/redis/connection.py", line 665, in _connect
    sock.connect(socket_address)
ConnectionRefusedError: [Errno 111] Connection refused

Today I am more flexible on the idea of having sessions / attached_sessions return [].

Caveat: that may not necessarily be the same as a client existing or not:

Assuming exit-empty is off (by default, it's on):

tmux start-server

The server would stay on, but return no sessions.

     start-server
                   (alias: start)
             Start the tmux server, if not already running, without creating any sessions.

             Note that as by default the tmux server will exit with no sessions, this is only useful if a session is
             created in ~/.tmux.conf, exit-empty is turned off, or another command is run as part of the same command
             sequence.  For example:

                   $ tmux start \; show -g