Catch UnknownSSHError and do not use return codes

The runners were still checking for the return codes of
create_ssh_master_connection instead of catching the exception.
We now catch the exceptions we calling the runners in main.

.gitignore

@@ -1,3 +1,4 @@
 poetry.lock
 __pycache__
 docs/build
+dist/

pyproject.toml

@@ -26,4 +26,6 @@ docs = [
     "sphinx (>=9.1.0,<10.0.0)",
     "sphinx-rtd-theme (>=3.0.2,<4.0.0)",
 ]
-
+dev = [
+    "pylint (>=4.0.4,<5.0.0)"
+]

src/unisync/config.py

@@ -2,7 +2,7 @@
 # SPDX-License-Identifier: GPL-3.0-or-later
 
 from configparser import UNNAMED_SECTION
-from dataclasses import dataclass, field
+from dataclasses import dataclass
 from pathlib import Path
 import ipaddress
 import configparser
@@ -30,8 +30,8 @@ class ServerConfig:
         if self.ip != "":
             try:
                 ipaddress.ip_address(self.ip)
-            except ValueError:
+            except ValueError as e:
-                raise ValueError("The provided ip address is invalid")
+                raise ValueError("The provided ip address is invalid") from e
 
 @dataclass
 class RootsConfig:
@@ -49,6 +49,18 @@ class UnisonConfig:
     bools: list
     values: dict
 
+@dataclass
+class BackupConfig:
+    """
+    Configuration options relative to backing up the files.
+    """
+    enabled: bool
+    selection: str
+    location: str
+    max_backups: int
+    backupsuffix: str
+    backupprefix: str
+
 @dataclass
 class OtherConfig:
     """
@@ -64,6 +76,7 @@ class Config:
     server: ServerConfig
     roots: RootsConfig
     unison: UnisonConfig
+    backup: BackupConfig
     other: OtherConfig
 
 
@@ -81,6 +94,7 @@ def load_config(config_path:str) -> Config:
     # Check if sections are provided
     server_section = "Server" if "Server" in config.sections() else UNNAMED_SECTION
     roots_section = "Roots" if "Roots" in config.sections() else UNNAMED_SECTION
+    backup_section = "Backup"
     other_section = "Other" if "Other" in config.sections() else UNNAMED_SECTION
 
     server_config = ServerConfig(
@@ -94,20 +108,28 @@ def load_config(config_path:str) -> Config:
             config.get(roots_section, "local", fallback=DEFAULT_ROOTS_LOCAL),
             config.get(roots_section, "remote")
         )
+    backup_config = BackupConfig(
+            config.getboolean(backup_section, "enabled", fallback=DEFAULT_BACKUP_ENABLED),
+            config.get(backup_section, "selection", fallback=DEFAULT_BACKUP_SELECTION),
+            config.get(backup_section, "loction", fallback=DEFAULT_BACKUP_LOC),
+            config.getint(backup_section, "max_backups", fallback=DEFAULT_BACKUP_MAX_BACKUPS),
+            config.get(backup_section, "backupsuffix", fallback=DEFAULT_BACKUP_BACKUPSUFFIX),
+            config.get(backup_section, "backupprefix", fallback=DEFAULT_BACKUP_BACKUPPREFIX)
+        )
     other_config = OtherConfig(
             Path(config.get(other_section, "cache_dir_path", fallback=DEFAULT_MISC_CACHE_DIR_PATH)).expanduser()
         )
 
-    args_bool = list()
+    args_bool = []
-    args_val = dict()
+    args_val = {}
     if "Unison" in config.sections():
         for key, val in config.items("Unison"):
             if key in config["DEFAULT"].keys():
                 continue
-            elif val == "" or val == None:
+            if val in ("", None):
                 args_bool.append(key)
             else:
                 args_val[key] = val
     unison_config = UnisonConfig(args_bool, args_val)
 
-    return Config(server_config, roots_config, unison_config, other_config)
+    return Config(server_config, roots_config, unison_config, backup_config, other_config)

src/unisync/defaults.py

@@ -1,4 +1,4 @@
-# copyright (c) 2026 paul retourné
+# Copyright (c) 2026 paul retourné
 # spdx-license-identifier: gpl-3.0-or-later
 
 from pathlib import Path
@@ -16,3 +16,10 @@ DEFAULT_ROOTS_LOCAL: str = str(Path("~/files").expanduser())
 # DEFAULT_ROOTS_REMOTE: str = ""
 
 DEFAULT_MISC_CACHE_DIR_PATH: str = "~/.unisync"
+
+DEFAULT_BACKUP_ENABLED: bool = False
+DEFAULT_BACKUP_SELECTION: str = ""
+DEFAULT_BACKUP_LOC: str = "local"
+DEFAULT_BACKUP_MAX_BACKUPS: int = 2
+DEFAULT_BACKUP_BACKUPSUFFIX: str = ".$VERSION.bak"
+DEFAULT_BACKUP_BACKUPPREFIX: str = ".unison_backups/"

src/unisync/errors.py

@@ -1,8 +1,21 @@
 # Copyright (C) 2025-2026 Paul Retourné
 # SPDX-License-Identifier: GPL-3.0-or-later
 
-class RemoteMountedError(BaseException):
+from typing import NoReturn
+import sys
+
+class RemoteMountedError(Exception):
     pass
 
-class InvalidMountError(BaseException):
+class InvalidMountError(Exception):
     pass
+
+class UnknownSSHError(Exception):
+    pass
+
+class FatalSyncError(Exception):
+    pass
+
+def unisync_exit_fatal(reason:str) -> NoReturn:
+    print(reason)
+    sys.exit(1)

src/unisync/main.py

@@ -1,29 +1,28 @@
 # Copyright (C) 2025-2026 Paul Retourné
 # SPDX-License-Identifier: GPL-3.0-or-later
 
-import os
 from pathlib import Path
 
 from unisync.argparser import create_argparser
+from unisync.errors import UnknownSSHError, unisync_exit_fatal
 from unisync.runners import unisync_sync, unisync_add, unisync_mount
 from unisync.config import load_config
 from unisync.synchroniser import Synchroniser
-from unisync.paths import *
+from unisync.paths import PathsManager
 
 def main():
     parser = create_argparser(unisync_sync, unisync_add, unisync_mount)
     cli_args = parser.parse_args()
 
-    config_path = os.path.expanduser("~/.config/unisync/config.ini")
+    config_path: Path = Path("~/.config/unisync/config.ini").expanduser()
     # Check if --config is set
-    if cli_args.config != None and os.path.isfile(cli_args.config):
+    if cli_args.config is not None and Path(cli_args.config).is_file():
         config = load_config(cli_args.config)
-    elif os.path.isfile(config_path):
+    elif config_path.is_file():
-        config = load_config(config_path)
+        config = load_config(str(config_path))
     else:
-        # TODO: replace the next line with something to do if no config file is found
+        # TODO replace the next line with something to do if no config file is found
-        config = load_config(config_path)
+        config = load_config(str(config_path))
-        pass
 
     # TODO: make the command line arguments work and override the config options
 
@@ -34,12 +33,16 @@ def main():
             config.server.ip if config.server.ip != "" else config.server.hostname,
             config.server.port,
             config.unison.bools,
-            config.unison.values
+            config.unison.values,
+            backup=config.backup
     )
 
     paths_manager = PathsManager(Path(config.roots.local), config.other.cache_dir_path)
 
-    cli_args.func(synchroniser, paths_manager)
+    try:
+        cli_args.func(synchroniser, paths_manager, config)
+    except UnknownSSHError:
+        unisync_exit_fatal("Connection failed quitting")
 
 
 if __name__ == "__main__":

src/unisync/paths.py

@@ -92,7 +92,7 @@ class PathsManager:
         Writes a list of new paths to the file
         """
         current_paths = self.get_paths_to_sync()
-        paths_to_add = list()
+        paths_to_add = []
         # Check if one of the parent is already being synchronised
         # If so there is no need to add the child path
         for new_path in paths:

src/unisync/runners.py

@@ -3,34 +3,41 @@
 
 from unisync.synchroniser import Synchroniser
 from unisync.paths import PathsManager
+from unisync.config import Config
 
 
-def unisync_sync(synchroniser:Synchroniser, paths_manager:PathsManager):
+def unisync_sync(synchroniser:Synchroniser, paths_manager:PathsManager, config: Config):
-    if synchroniser.create_ssh_master_connection() != 0:
+    del config # The function signature must be the same for all runners
-        print("Connection failed quitting")
+
-        return 1
+    synchroniser.create_ssh_master_connection()
     print("Connected to the remote.")
 
     synchroniser.sync_files(paths_manager.get_paths_to_sync())
     synchroniser.sync_links(paths_manager.get_paths_to_sync())
 
-    # TODO: check the config options and do or don't do the following
+    # TODO check the config options and do or don't do the following
     synchroniser.update_links()
     #synchroniser.mount_remote_dir()
 
     synchroniser.close_ssh_master_connection()
 
 
-def unisync_add(synchroniser:Synchroniser, paths_manager:PathsManager):
+def unisync_add(synchroniser:Synchroniser, paths_manager:PathsManager, config: Config):
-    if synchroniser.create_ssh_master_connection() != 0:
+    del config # The function signature must be the same for all runners
-        print("Connection failed quitting")
+
-        return 1
+    synchroniser.create_ssh_master_connection()
     print("Connected to the remote.")
 
+    # TODO config or cli to skip this first sync
+    synchroniser.sync_files(paths_manager.get_paths_to_sync())
+
     paths_manager.add_files_to_sync()
+    synchroniser.sync_files(paths_manager.get_paths_to_sync(), force=True)
 
     synchroniser.close_ssh_master_connection()
 
 
-def unisync_mount(synchroniser:Synchroniser, paths_manager:PathsManager):
+def unisync_mount(synchroniser:Synchroniser, paths_manager:PathsManager, config: Config):
+    del paths_manager # The function signature must be the same for all runners
+    del config # The function signature must be the same for all runners
     synchroniser.mount_remote_dir()

src/unisync/synchroniser.py

@@ -14,8 +14,10 @@ import time
 import logging
 
 from pathlib import Path
+from typing import cast
 
-from unisync.errors import RemoteMountedError, InvalidMountError
+from unisync.errors import RemoteMountedError, InvalidMountError, UnknownSSHError, FatalSyncError
+from unisync.config import BackupConfig
 
 logger = logging.getLogger(__name__)
 
@@ -47,8 +49,10 @@ class Synchroniser:
             Currently unused.
     """
 
-    def __init__(self, remote:str, local:str, user:str, ip:str,
+    def __init__(self, remote:str, local:str, user:str, ip:str, port:int=22,
-                 port:int=22, args_bool:list=[], args_value:dict={}, ssh_settings:dict={}):
+                 args_bool:list=[], args_value:dict={}, ssh_settings:dict={},
+                 backup:BackupConfig | None = None
+                 ):
         """Initialises an instance of Synchroniser.
         """
         self.remote_dir:str = remote
@@ -59,8 +63,36 @@ class Synchroniser:
         self.remote_user:str = user
         self.remote_ip:str = ip 
         self.remote_port:int = port
+        self.files_extra:list = list()
+        self.links_extra:list = list()
 
-    def create_ssh_master_connection(self, control_path:str="~/.ssh/control_%C", connection_timeout:int=60) -> int:
+        if(backup != None and backup.enabled):
+            backup = cast(BackupConfig, backup)
+            self.files_extra.append("-backup")
+            if(backup.selection != ""):
+                self.files_extra.append(backup.selection)
+            else:
+                self.files_extra.append("Name *")
+
+            self.files_extra.extend([
+                "-backuploc",
+                backup.location,
+                "-maxbackups",
+                str(backup.max_backups),
+                "-backupsuffix",
+                backup.backupsuffix,
+                "-backupprefix",
+                backup.backupprefix,
+                "-ignore",
+                f"Name {backup.backupprefix[:-1]}"
+            ])
+
+            self.links_extra.extend([
+                "-ignore",
+                f"Name {backup.backupprefix[:-1]}"
+                ])
+    
+    def create_ssh_master_connection(self, control_path:str="~/.ssh/control_%C", connection_timeout:int=60) -> None:
         """Creates an ssh master connection.
 
         It is used so the user only has to authenticate once to the remote server.
@@ -73,8 +105,14 @@ class Synchroniser:
             connection_timeout:
                 Time given to the user to authenticate to the remote server.
                 On slow connections one might want to increase this.
-        Returns:
+
-            An error code (0 success, 1 TimeoutExpired, 2 KeyboardInterrupt).
+        Raises:
+            subprocess.TimeoutExpired:
+                The user didn't finish loging in in time.
+            KeyboardInterrupt:
+                The user interrupted the process.
+            UnknownSSHError:
+                An error occured during the connection.
         """
         self.control_path = os.path.expanduser(control_path)
         command = [
@@ -89,16 +127,15 @@ class Synchroniser:
         # TODO: Raise an exception instead of changing the return value
         try:
             ret_code = master_ssh.wait(timeout=connection_timeout)
-        except subprocess.TimeoutExpired:
+        except subprocess.TimeoutExpired as e:
             print("Time to login expired", file=sys.stderr)
-            return 1
+            raise e
-        except KeyboardInterrupt:
+        except KeyboardInterrupt as e:
-            return 2
+            raise e
 
         if ret_code != 0:
             print("Login to remote failed", file=sys.stderr)
-            return ret_code
+            raise UnknownSSHError
-        return 0
 
 
     def close_ssh_master_connection(self) -> int:
@@ -117,40 +154,45 @@ class Synchroniser:
         close = subprocess.Popen(command)
         return close.wait()
 
-    def sync_files(self, paths:list, force:bool=False) -> int:
+    def sync_files(self, paths:list, force:bool=False) -> None:
         """Synchronises the files.
 
         Args:
             paths: List of paths to synchronise.
             force: Force the changes from remote to local.
 
-        Returns:
+        Raises:
-            The return code of sync.
+            FatalSyncError: A fatal error occured during the synchronisation.
         """
-        return self.sync(
+
+        self.sync(
                 f"ssh://{self.remote_user}@{self.remote_ip}/{self.remote_dir}/.data",
                 self.local,
                 paths=paths,
-                force=force
+                force=force,
+                other=self.files_extra
                 )
 
-    def sync_links(self, ignore:list) -> int:
+    def sync_links(self, ignore:list) -> None:
         """Synchronises the links, they must exist already.
 
         Args:
             ignore: List of paths to ignore.
 
-        Returns:
+        Raises:
-            The return code of sync.
+            FatalSyncError: A fatal error occured during the synchronisation.
         """
-        return self.sync(
+        self.sync(
                 f"ssh://{self.remote_user}@{self.remote_ip}/{self.remote_dir}/links",
                 self.local,
-                ignore=ignore
+                ignore=ignore,
+                other=self.links_extra
                 )
 
     def sync(self, remote_root:str, local_root:str,
-             paths:list=[], ignore:list=[], force:bool=False) -> int:
+             paths:list=[], ignore:list=[], force:bool=False,
+             other:list=[]
+             ) -> None:
         """Performs the synchronisation by calling unison.
 
         Args:
@@ -162,9 +204,18 @@ class Synchroniser:
                 If you need to ignore some specific files use the arguments.
             force: Force all changes from remote to local.
                 Used mostly when replacing a link by the file.
+            other:
+                Other arguments to add to unison.
+                These arguments will only be used for this sync which is not
+                the case for the ones in self.args_bool and self.args_value.
+                They will be added to the command as is no - in front.
+                For exemple backups are implemented using this argument.
 
-        Returns:
+        Raises:
-            the unison return code see section 6.11 of the documentation
+            FatalSyncError:
+                If unison returns 3 it means either a fatal error occured or the synchronisation
+                was interrupted.
+                If this happens propagate the error to unisync.
         """
         command = [ "/usr/bin/unison", "-root", remote_root, "-root", local_root ]
         for arg in self.args_bool:
@@ -174,6 +225,7 @@ class Synchroniser:
             command.append(value)
 
         sshargs = f"-p {self.remote_port} "
+        sshargs += f"-S {self.control_path} "
         for arg, value in self.ssh_settings.items():
             sshargs += arg + " " + value + " "
         command.append("-sshargs")
@@ -188,13 +240,17 @@ class Synchroniser:
             command.append(f"BelowPath {path}")
 
         if force:
-            command.append("-force")
+            command.append("-prefer")
             command.append(remote_root)
             command.append("-batch")
 
+        for arg in other:
+            command.append(arg)
+
         proc = subprocess.Popen(command)
         ret_code = proc.wait()
-        return ret_code
+        if ret_code == 3:
+            raise FatalSyncError("Synchronisation could not be completed")
 
     def update_links(self, background:bool=True):
         """Updates the links on the remote.
@@ -223,7 +279,7 @@ class Synchroniser:
                 link_background_wrapper
                 ]
 
-        link_update_process = subprocess.Popen(command, stdout=subprocess.DEVNULL, stderr=subprocess.DEVNULL)
+        link_update_process = subprocess.run(command, stdout=subprocess.DEVNULL, stderr=subprocess.DEVNULL)
 
         if not background:
             print("Starting links update.")

tests/runners.py

@@ -0,0 +1,8 @@
+# Copyright (C) 2026 Paul Retourné
+# SPDX-License-Identifier: GPL-3.0-or-later
+
+from unisync.synchroniser import Synchroniser
+from unisync.paths import PathsManager
+
+def unisync_test(synchroniser:Synchroniser, paths_manager:PathsManager):
+    print("Testing")

tests/test.py

@@ -0,0 +1,39 @@
+# Copyright (C) 2026 Paul Retourné
+# SPDX-License-Identifier: GPL-3.0-or-later
+
+import os
+from pathlib import Path
+
+from unisync.argparser import create_argparser
+from unisync.runners import unisync_sync, unisync_add, unisync_mount
+from unisync.config import load_config
+from unisync.synchroniser import Synchroniser
+from unisync.paths import *
+
+from runners import *
+
+def main():
+    parser = create_argparser(unisync_test, unisync_add, unisync_mount)
+    cli_args = parser.parse_args()
+
+    config_path = os.path.expanduser("./config.ini")
+    config = load_config(config_path)
+
+    print(config)
+
+    synchroniser = Synchroniser(
+            config.roots.remote,
+            config.roots.local,
+            config.server.user,
+            config.server.ip if config.server.ip != "" else config.server.hostname,
+            config.server.port,
+            config.unison.bools,
+            config.unison.values
+    )
+
+    paths_manager = PathsManager(Path(config.roots.local), config.other.cache_dir_path)
+
+    cli_args.func(synchroniser, paths_manager)
+
+if __name__ == "__main__":
+    main()