Adds error handling for the paths

src/unisync/synchroniser.py

@@ -9,6 +9,8 @@ import logging
 
 from pathlib import Path
 
+from errors import RemoteMountedError, InvalidMountError
+
 logger = logging.getLogger(__name__)
 
 class Synchroniser:
@@ -175,16 +177,24 @@ class Synchroniser:
         Mount the remote directory to make the local links work.
         This is achieved using sshfs.
         Raise:
+        - RemoteMountedError: The .data directory is already a mount point
+        - InvalidMountError: .data is either not a directory or not empty
         - subprocess.CalledProcessError: An error occured with sshfs
         """
+        # Get the absolute path to the correct .data directory resolving symlinks
+        path_to_mount:PosixPath = Path(f"{self.local}/../.data").resolve()
+        if path_to_mount.is_mount():
+            raise RemoteMountedError
+        # Check if it is an empty directory
+        if not path_to_mount.is_dir() or any(path_to_mount.iterdir()):
+            raise InvalidMountError
         command = [
                 "/usr/bin/sshfs",
                 "-o", "ControlPath={self.control_path}",
                 "-o", "ServerAliveInterval=15",
                 "-p", str(self.remote_port),
                 f"{self.remote_user}@{self.remote_ip}:{self.remote_dir}/.data",
-                # Get the absolute path to the correct .data directory resolving symlinks
-                str(Path(f"{self.local}/../.data").resolve())
+                str(path_to_mount)
                 ]
         completed_process = subprocess.run(command)
         completed_process.check_returncode()