Unreachable fsync call in SysCommandWorker.write

[correctmost]

Description

pylint --enable=unreachable . picks up the following unreachable fsync call:

archinstall/archinstall/lib/general.py

Lines 217 to 219 in 7437668

	if self.child_fd:
	return os.write(self.child_fd, data + (b'\n' if line_ending else b''))
	os.fsync(self.child_fd)

Warning

************* Module archinstall.lib.general
archinstall/lib/general.py:219:3: W0101: Unreachable code (unreachable)

[Torxed]

That's because pty.fork() secondary executor will be the thing that performs that call.
Maybe pylint can't handle forked code?

[correctmost]

Hmm, mypy also flags that line as unreachable:

archinstall/lib/general.py:219: error: Statement is unreachable  [unreachable]

I tried this sample code to try to understand the semantics better:

import os
import pty

def write():
    return os.write(fd, b"foo")
    raise AssertionError
    os.fsync(fd)

pid, fd = pty.fork()
write()

The code doesn't seem to trigger the AssertionError, which makes me think the fsync call might not actually be performed.

I was thinking the archinstall code needed to be updated like the following, but I might be misunderstanding the existing command worker code:

 if self.child_fd: 
 	bytes_written = os.write(self.child_fd, data + (b'\n' if line_ending else b'')) 
 	os.fsync(self.child_fd)
        return bytes_written

[Torxed]

That example has no check if the code is executed in the parent or forked child.

Both threads will call write(), whereas I check if we have a pid, and only the child process will have something there, the parent won't and thus skips that part of the code.

import pty
import random

pid, fd = pty.fork()

with open(f"/tmp/pid_{random.randint(0, 2000)}", "w") as fh:
    fh.write(f"pid: {pid}, fd: {fd}")

Both threads will execute, but with different values :)

[correctmost]

Thanks, the forking part makes sense :).

I think the main item of confusion for me is how the os.fsync call on 219 can be reached after a return statement on line 218:

archinstall/archinstall/lib/general.py

Lines 217 to 219 in 7437668

	if self.child_fd:
	return os.write(self.child_fd, data + (b'\n' if line_ending else b''))
	os.fsync(self.child_fd)

My understanding is that the return would stop further execution regardless of whether the code is executed by the child or parent process.

We can suppress the pylint and mypy warnings for line 219, but I would want to make sure it's a true false positive. Thanks!

[Torxed]

Ah yeah that return never happens, sorry about that one hehe.
We can either move that line up or remove it all together