synchroniser : misc pylint suggested fixes

- Do not use mutables as default arguments
- Remove trailing whitespaces
- Initialise using [] and {} instead of list() and dict()
- Use is not None instead of != None
- Some other small stuff

src/unisync/synchroniser.py

@@ -10,7 +10,6 @@ the remote.
 import subprocess
 import os
 import sys
-import time
 import logging
 
 from pathlib import Path
@@ -50,26 +49,27 @@ class Synchroniser:
     """
 
     def __init__(self, remote:str, local:str, user:str, ip:str, port:int=22,
-                 args_bool:list=[], args_value:dict={}, ssh_settings:dict={},
+                 args_bool:list[str] | None = None, args_value:dict[str, str] | None = None,
-                 backup:BackupConfig | None = None
+                 ssh_settings:dict[str, str] | None = None, backup:BackupConfig | None = None
                  ):
         """Initialises an instance of Synchroniser.
         """
         self.remote_dir:str = remote
         self.local:str = local
-        self.args_bool:list[str] = args_bool 
+        self.args_bool:list[str] = args_bool if args_bool is not None else []
-        self.args_value:dict[str, str] = args_value 
+        self.args_value:dict[str, str] = args_value if args_value is not None else {}
-        self.ssh_settings:dict[str, str] = dict()
+        self.ssh_settings:dict[str, str] = ssh_settings if ssh_settings is not None else {}
         self.remote_user:str = user
         self.remote_ip:str = ip
         self.remote_port:int = port
-        self.files_extra:list = list()
+        self.files_extra:list = []
-        self.links_extra:list = list()
+        self.links_extra:list = []
+        self.control_path:str = ""
 
-        if(backup != None and backup.enabled):
+        if backup is not None and backup.enabled:
             backup = cast(BackupConfig, backup)
             self.files_extra.append("-backup")
-            if(backup.selection != ""):
+            if backup.selection != "":
                 self.files_extra.append(backup.selection)
             else:
                 self.files_extra.append("Name *")
@@ -92,7 +92,9 @@ class Synchroniser:
                 f"Name {backup.backupprefix[:-1]}"
                 ])
 
-    def create_ssh_master_connection(self, control_path:str="~/.ssh/control_%C", connection_timeout:int=60) -> None:
+    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.
@@ -123,7 +125,7 @@ class Synchroniser:
                 f"{self.remote_user}@{self.remote_ip}",
                 "-p", str(self.remote_port)
                 ]
-        master_ssh = subprocess.Popen(command)
+        with subprocess.Popen(command) as master_ssh:
             # TODO: Raise an exception instead of changing the return value
             try:
                 ret_code = master_ssh.wait(timeout=connection_timeout)
@@ -151,8 +153,10 @@ class Synchroniser:
                 f"{self.remote_user}@{self.remote_ip}",
                 "-p", str(self.remote_port)
                 ]
-        close = subprocess.Popen(command)
+        with subprocess.Popen(command) as close:
-        return close.wait()
+            retval = close.wait()
+
+        return retval
 
     def sync_files(self, paths:list, force:bool=False) -> None:
         """Synchronises the files.
@@ -190,8 +194,8 @@ class Synchroniser:
                 )
 
     def sync(self, remote_root:str, local_root:str,
-             paths:list=[], ignore:list=[], force:bool=False,
+             paths:list | None=None, ignore:list | None = None, force:bool=False,
-             other:list=[]
+             other:list | None = None
              ) -> None:
         """Performs the synchronisation by calling unison.
 
@@ -217,6 +221,13 @@ class Synchroniser:
                 was interrupted.
                 If this happens propagate the error to unisync.
         """
+        if paths is None:
+            paths = []
+        if ignore is None:
+            ignore = []
+        if other is None:
+            other = []
+
         command = [ "/usr/bin/unison", "-root", remote_root, "-root", local_root ]
         for arg in self.args_bool:
             command.append(f"-{arg}")
@@ -247,8 +258,10 @@ class Synchroniser:
         for arg in other:
             command.append(arg)
 
-        proc = subprocess.Popen(command)
+        with subprocess.Popen(command) as proc:
             ret_code = proc.wait()
+
+        # See unison manual section 6.11
         if ret_code == 3:
             raise FatalSyncError("Synchronisation could not be completed")
 
@@ -279,12 +292,12 @@ class Synchroniser:
                 link_background_wrapper
                 ]
 
-        link_update_process = subprocess.run(command, stdout=subprocess.DEVNULL, stderr=subprocess.DEVNULL)
+        print("Updating links")
-
+        subprocess.run(command,
-        if not background:
+                       stdout=subprocess.DEVNULL,
-            print("Starting links update.")
+                       stderr=subprocess.DEVNULL,
-            link_update_process.wait()
+                       check=False
-            print("Done")
+                       )
 
     def mount_remote_dir(self):
         """Mounts the remote directory to make the local links work.
@@ -311,5 +324,5 @@ class Synchroniser:
                 f"{self.remote_user}@{self.remote_ip}:{self.remote_dir}/.data",
                 str(path_to_mount)
                 ]
-        completed_process = subprocess.run(command)
+        completed_process = subprocess.run(command, check=True)
         completed_process.check_returncode()