pathlib.Path.copy() hangs on FIFO pipes and loops infinitely on /dev/zero

Bug Description

pathlib.Path.copy() (introduced recently) attempts to open and copy any file type that is not a directory or a symlink. This causes severe issues with special files:

1. FIFOs (Named Pipes): Opening a FIFO for reading blocks indefinitely if there is no writer, causing the process to hang using CPU.
2. Infinite Sources: Reading from character devices like /dev/zero results in an infinite loop, potentially filling up the disk or freezing the application.

shutil.copyfile correctly handles this by raising SpecialFileError (or similar) when encountering these files. pathlib should behave similarly or at least safely.

Reproduction

import os
import pathlib
import signal
import time

fifo_name = "test_fifo_hang"
if os.path.exists(fifo_name):
    os.remove(fifo_name)
os.mkfifo(fifo_name)

# This will hang indefinitely
print("Attempting to copy FIFO...")
p = pathlib.Path(fifo_name)
try:
    p.copy("test_fifo_dest") 
except Exception as e:
    print(f"Caught: {e}")
else:
    print("Copy finished (unexpected!)")
finally:
    os.remove(fifo_name)

Expected Behavior

The operation should fail immediately with io.UnsupportedOperation or shutil.SameFileError / SpecialFileError instead of hanging or looping.

Proposed Solution

Check is_file() in pathlib.Path.copy (specifically _copy_from) to ensure we only copy regular files.

I have a PR ready for this.

CPython versions tested on:

3.14

Operating systems tested on:

macOS

Linked PRs

• gh-143966

Empieza en pathlib.Path.copy(), concretamente en _copy_from, y compara su gestión con el comportamiento de shutil.copyfile ante SpecialFileError. Reproduce los casos FIFO y /dev/zero; se considera terminado cuando ambos fallan rápidamente sin bloquearse ni consumir datos sin límite, con cobertura de regresión para este comportamiento.