Re: [PATCH 2/4] python/console_socket: accept existing FD in initializer

[Daniel P . Berrangé]

On Thu, Jul 20, 2023 at 09:04:46AM -0400, John Snow wrote:
> Useful if we want to use ConsoleSocket() for a socket created by
> socketpair().
> 
> Signed-off-by: John Snow <jsnow@redhat.com>
> ---
>  python/qemu/machine/console_socket.py | 11 +++++++----
>  1 file changed, 7 insertions(+), 4 deletions(-)
> 
> diff --git a/python/qemu/machine/console_socket.py 
> b/python/qemu/machine/console_socket.py
> index 4e28ba9bb2..42bfa12411 100644
> --- a/python/qemu/machine/console_socket.py
> +++ b/python/qemu/machine/console_socket.py
> @@ -17,7 +17,7 @@
>  import socket
>  import threading
>  import time
> -from typing import Deque, Optional
> +from typing import Deque, Optional, Union
>  
>  
>  class ConsoleSocket(socket.socket):
> @@ -30,13 +30,16 @@ class ConsoleSocket(socket.socket):
>      Optionally a file path can be passed in and we will also
>      dump the characters to this file for debugging purposes.
>      """
> -    def __init__(self, address: str, file: Optional[str] = None,
> +    def __init__(self, address: Union[str, int], file: Optional[str] = None,
>                   drain: bool = False):

IMHO calling the pre-opened FD an "address" is pushing the
interpretation a bit.

It also makes the behaviour non-obvious from a caller. Seeing a
caller, you have to work backwards to find out what type it has,
to figure out the semantics of the method call.

IOW, I'd prefer to see

   address: Optional[str], sock_fd: Optional[int]

and then just do a check

   if (address is not None and sock_fd is not None) or
      (address is None and sock_fd is None):
      raise Exception("either 'address' or 'sock_fd' is required")

thus when you see

   ConsoleSocket(sock_fd=xxx)

it is now obvious it has different behaviour to

   ConsoleSocket(address=yyy)


>          self._recv_timeout_sec = 300.0
>          self._sleep_time = 0.5
>          self._buffer: Deque[int] = deque()
> -        socket.socket.__init__(self, socket.AF_UNIX, socket.SOCK_STREAM)
> -        self.connect(address)
> +        if isinstance(address, str):
> +            socket.socket.__init__(self, socket.AF_UNIX, socket.SOCK_STREAM)
> +            self.connect(address)
> +        else:
> +            socket.socket.__init__(self, fileno=address)
>          self._logfile = None
>          if file:
>              # pylint: disable=consider-using-with
> -- 
> 2.41.0
> 

With regards,
Daniel
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