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/

docs/Makefile

@@ -0,0 +1,20 @@
+# Minimal makefile for Sphinx documentation
+#
+
+# You can set these variables from the command line, and also
+# from the environment for the first two.
+SPHINXOPTS    ?=
+SPHINXBUILD   ?= sphinx-build
+SOURCEDIR     = source
+BUILDDIR      = build
+
+# Put it first so that "make" without argument is like "make help".
+help:
+	@$(SPHINXBUILD) -M help "$(SOURCEDIR)" "$(BUILDDIR)" $(SPHINXOPTS) $(O)
+
+.PHONY: help Makefile
+
+# Catch-all target: route all unknown targets to Sphinx using the new
+# "make mode" option.  $(O) is meant as a shortcut for $(SPHINXOPTS).
+%: Makefile
+	@$(SPHINXBUILD) -M $@ "$(SOURCEDIR)" "$(BUILDDIR)" $(SPHINXOPTS) $(O)

docs/make.bat

@@ -0,0 +1,35 @@
+@ECHO OFF
+
+pushd %~dp0
+
+REM Command file for Sphinx documentation
+
+if "%SPHINXBUILD%" == "" (
+	set SPHINXBUILD=sphinx-build
+)
+set SOURCEDIR=source
+set BUILDDIR=build
+
+%SPHINXBUILD% >NUL 2>NUL
+if errorlevel 9009 (
+	echo.
+	echo.The 'sphinx-build' command was not found. Make sure you have Sphinx
+	echo.installed, then set the SPHINXBUILD environment variable to point
+	echo.to the full path of the 'sphinx-build' executable. Alternatively you
+	echo.may add the Sphinx directory to PATH.
+	echo.
+	echo.If you don't have Sphinx installed, grab it from
+	echo.https://www.sphinx-doc.org/
+	exit /b 1
+)
+
+if "%1" == "" goto help
+
+%SPHINXBUILD% -M %1 %SOURCEDIR% %BUILDDIR% %SPHINXOPTS% %O%
+goto end
+
+:help
+%SPHINXBUILD% -M help %SOURCEDIR% %BUILDDIR% %SPHINXOPTS% %O%
+
+:end
+popd

docs/source/conf.py

@@ -0,0 +1,36 @@
+# Configuration file for the Sphinx documentation builder.
+#
+# For the full list of built-in configuration values, see the documentation:
+# https://www.sphinx-doc.org/en/master/usage/configuration.html
+
+# -- Project information -----------------------------------------------------
+# https://www.sphinx-doc.org/en/master/usage/configuration.html#project-information
+
+project = 'unisync'
+copyright = '2026, Paul Retourné'
+author = 'Paul Retourné'
+release = '0.1.0'
+
+# -- General configuration ---------------------------------------------------
+# https://www.sphinx-doc.org/en/master/usage/configuration.html#general-configuration
+
+extensions = [
+    'sphinx.ext.autodoc',
+    'sphinx.ext.viewcode',
+    'sphinx.ext.napoleon',
+    'sphinx.ext.todo'
+        ]
+
+templates_path = ['_templates']
+exclude_patterns = []
+
+
+
+# -- Options for HTML output -------------------------------------------------
+# https://www.sphinx-doc.org/en/master/usage/configuration.html#options-for-html-output
+
+#html_theme = 'alabaster'
+html_theme = 'sphinx_rtd_theme'
+html_static_path = ['_static']
+
+autodoc_docstring_signature = True

docs/source/example.rst

@@ -0,0 +1,24 @@
+.. _example_how_it_works:
+
+Example of how unisync works
+============================
+
+Let's say you have the following structure::
+
+        $ tree .
+        .
+        ├── big_file
+        └── folder
+            ├── file
+            └── other_file
+
+If you only want to synchronise `folder` and its content on your laptop the following will be automatically generated::
+
+        $ tree .
+        .
+        ├── big_file -> ../.data/big_file
+        └── folder
+            ├── file
+            └── other_file
+
+`big_file` is now a symbolic link and by mounting the remote directory you can still seemlessly access `big_file` through the network.

docs/source/index.rst

@@ -0,0 +1,31 @@
+.. unisync documentation master file, created by
+   sphinx-quickstart on Sun Jan  4 15:02:58 2026.
+   You can adapt this file completely to your liking, but it should at least
+   contain the root `toctree` directive.
+
+Documentation for unisync
+=========================
+
+Unisync is a data synchronising tool built around `unison`_ and expending on it.
+
+Unisync tries to solve two problems that are often solved separately but never together :
+
+* Keeping your data synchronised between multiple machines (through a central server), examples of this are rsync and of course unison.
+* Being able to access and edit files stored on your server without having to download them, the gui interface of nextcloud for example.
+* And of course I want to be able to do all of this without ever having to leave my terminal.
+
+Unisync solves this problem by placing each file on your local machine but with only the selected files and folders being physically present on your drive,
+the others are replaced by symbolic links pointing to a directory that is mounted from your server.
+
+See this
+:ref:`example_how_it_works`.
+
+.. _unison: https://github.com/bcpierce00/unison
+
+.. toctree::
+   :maxdepth: 2
+   :caption: Contents:
+
+   example
+   modules
+

docs/source/modules.rst

@@ -0,0 +1,7 @@
+unisync
+=======
+
+.. toctree::
+   :maxdepth: 4
+
+   unisync

docs/source/unisync.rst

@@ -0,0 +1,77 @@
+unisync package
+===============
+
+Submodules
+----------
+
+unisync.argparser module
+------------------------
+
+.. automodule:: unisync.argparser
+   :members:
+   :show-inheritance:
+   :undoc-members:
+
+unisync.config module
+---------------------
+
+.. automodule:: unisync.config
+   :members:
+   :show-inheritance:
+   :undoc-members:
+
+unisync.defaults module
+-----------------------
+
+.. automodule:: unisync.defaults
+   :members:
+   :show-inheritance:
+   :undoc-members:
+
+unisync.errors module
+---------------------
+
+.. automodule:: unisync.errors
+   :members:
+   :show-inheritance:
+   :undoc-members:
+
+unisync.main module
+-------------------
+
+.. automodule:: unisync.main
+   :members:
+   :show-inheritance:
+   :undoc-members:
+
+unisync.paths module
+--------------------
+
+.. automodule:: unisync.paths
+   :members:
+   :show-inheritance:
+   :undoc-members:
+
+unisync.runners module
+----------------------
+
+.. automodule:: unisync.runners
+   :members:
+   :show-inheritance:
+   :undoc-members:
+
+unisync.synchroniser module
+---------------------------
+
+.. automodule:: unisync.synchroniser
+   :members:
+   :show-inheritance:
+   :undoc-members:
+
+Module contents
+---------------
+
+.. automodule:: unisync
+   :members:
+   :show-inheritance:
+   :undoc-members:

pyproject.toml

@@ -20,3 +20,12 @@ packages = [{include = "unisync", from = "src"}]
 [build-system]
 requires = ["poetry-core>=2.0.0,<3.0.0"]
 build-backend = "poetry.core.masonry.api"
+
+[dependency-groups]
+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:
@@ -120,13 +120,13 @@ def load_config(config_path:str) -> Config:
             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

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
@@ -6,7 +6,7 @@ from pathlib import Path
 # Commented out values are part of the config but are required so there is no defaults.
 # This allows this file to be a list of all the config options.
 
-# DEFAULT_SERVER_USER: str = "" 
+# DEFAULT_SERVER_USER: str = ""
 DEFAULT_SERVER_SSHARGS: str = ""
 DEFAULT_SERVER_HOSTNAME: str = ""
 DEFAULT_SERVER_IP: str = ""

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

@@ -4,10 +4,11 @@
 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)
@@ -15,16 +16,15 @@ def main():
 
     config_path: Path = Path("~/.config/unisync/config.ini").expanduser()
     # Check if --config is set
-    if cli_args.config != None and Path(cli_args.config).is_file():
+    if cli_args.config is not None and Path(cli_args.config).is_file():
         config = load_config(cli_args.config)
     elif config_path.is_file():
         config = load_config(str(config_path))
     else:
         # TODO replace the next line with something to do if no config file is found
         config = load_config(str(config_path))
-        pass
 
-    # TODO make the command line arguments work and override the config options
+    # TODO: make the command line arguments work and override the config options
 
     synchroniser = Synchroniser(
             config.roots.remote,
@@ -39,7 +39,10 @@ def main():
 
     paths_manager = PathsManager(Path(config.roots.local), config.other.cache_dir_path)
 
-    cli_args.func(synchroniser, paths_manager, config)
+    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

@@ -5,15 +5,16 @@ from unisync.synchroniser import Synchroniser
 from unisync.paths import PathsManager
 from unisync.config import Config
 
+
 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
     synchroniser.update_links()
     #synchroniser.mount_remote_dir()
@@ -23,9 +24,8 @@ def unisync_sync(synchroniser:Synchroniser, paths_manager:PathsManager, config:
 
 def unisync_add(synchroniser:Synchroniser, paths_manager:PathsManager, config: Config):
     del config # The function signature must be the same for all runners
-    if synchroniser.create_ssh_master_connection() != 0:
+
-        print("Connection failed quitting")
+    synchroniser.create_ssh_master_connection()
-        return 1
     print("Connected to the remote.")
 
     # TODO config or cli to skip this first sync

src/unisync/synchroniser.py

@@ -16,7 +16,7 @@ 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__)
@@ -92,7 +92,7 @@ class Synchroniser:
                 f"Name {backup.backupprefix[:-1]}"
                 ])
     
-    def create_ssh_master_connection(self, control_path:str="~/.ssh/control_%C", connection_timeout:int=60) -> int:
+    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.
@@ -105,9 +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:
-            TODO change that to raising the exception.
+            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 = [
@@ -119,18 +124,18 @@ class Synchroniser:
                 "-p", str(self.remote_port)
                 ]
         master_ssh = subprocess.Popen(command)
+        # 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:
@@ -149,18 +154,18 @@ 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,
@@ -168,16 +173,16 @@ class Synchroniser:
                 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,
@@ -187,7 +192,7 @@ class Synchroniser:
     def sync(self, remote_root:str, local_root:str,
              paths:list=[], ignore:list=[], force:bool=False,
              other:list=[]
-             ) -> int:
+             ) -> None:
         """Performs the synchronisation by calling unison.
 
         Args:
@@ -206,8 +211,11 @@ class Synchroniser:
                 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:
@@ -217,6 +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")
@@ -231,7 +240,7 @@ class Synchroniser:
             command.append(f"BelowPath {path}")
 
         if force:
-            command.append("-force")
+            command.append("-prefer")
             command.append(remote_root)
             command.append("-batch")
 
@@ -240,7 +249,8 @@ class Synchroniser:
 
         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.
@@ -269,7 +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.")