Add type hints to the config reading functions

Return a TypedDict from _read_config() and stop reusing variables for different types, so that mypy can check the config values. No change in behaviour.

simple_backup/simple_backup.py

@@ -18,7 +18,7 @@ from __future__ import annotations
 import sys
 import os
 import pwd
-from typing import Callable, List, Optional, ParamSpec, TypeVar, Union
+from typing import Callable, List, Optional, ParamSpec, TypedDict, TypeVar, Union
 import warnings
 from functools import wraps
 from shutil import rmtree, which
@@ -766,8 +766,8 @@ def _expand_home(path: str, user: str) -> str:
     return os.path.expanduser(path)
 
 
-def _expand_inputs(inputs, user: Optional[str] = None):
-    expanded_inputs = []
+def _expand_inputs(inputs: List[str], user: Optional[str] = None) -> List[str]:
+    expanded_inputs: List[str] = []
 
     for i in inputs:
         if i == '':
@@ -790,8 +790,30 @@ def _expand_inputs(inputs, user: Optional[str] = None):
     return expanded_inputs
 
 
-def _read_config(config_file, user: Optional[str] = None):
-    config_args = {'inputs': None,
+class ConfigArgs(TypedDict):
+    """Values read from the configuration file"""
+
+    inputs: Optional[List[str]]
+    output: Optional[str]
+    exclude: Optional[List[str]]
+    keep: int
+    ssh_host: Optional[str]
+    ssh_user: Optional[str]
+    ssh_keyfile: Optional[str]
+    remote_sudo: bool
+    numeric_ids: bool
+
+
+def _get_bool(config: configparser.ConfigParser, key: str) -> bool:
+    # Empty values (as in the example config) count as false
+    if config.get('server', key, fallback='').strip() == '':
+        return False
+
+    return config.getboolean('server', key)
+
+
+def _read_config(config_file: str, user: Optional[str] = None) -> ConfigArgs:
+    config_args: ConfigArgs = {'inputs': None,
                                'output': None,
                                'exclude': None,
                                'keep': -1,
@@ -823,29 +845,15 @@ def _read_config(config_file, user: Optional[str] = None):
         section = 'default'
         inputs = config.get(section, 'inputs')
 
-    inputs = [i.strip() for i in inputs.split(',')]
-    inputs = _expand_inputs(inputs, user)
-    inputs = list(set(inputs))
-
-    config_args['inputs'] = inputs
+    config_args['inputs'] = list(set(_expand_inputs([i.strip() for i in inputs.split(',')], user)))
 
     # '~' is expanded later, since for remote backups it refers to the home on the server
     config_args['output'] = config.get(section, 'backup_dir')
 
-    try:
-        exclude = config.get(section, 'exclude')
-        exclude = [e.strip() for e in exclude.split(',') if e.strip() != '']
-    except configparser.NoOptionError:
-        exclude = []
+    exclude = config.get(section, 'exclude', fallback='')
+    config_args['exclude'] = [e.strip() for e in exclude.split(',') if e.strip() != '']
 
-    config_args['exclude'] = exclude
-
-    try:
-        keep = config.getint(section, 'keep')
-    except configparser.NoOptionError:
-        keep = -1
-
-    config_args['keep'] = keep
+    config_args['keep'] = config.getint(section, 'keep', fallback=-1)
 
     # Read host and user separately, so that a missing one is reported instead of silently
     # disabling remote backup. Empty values count as not set
@@ -854,12 +862,8 @@ def _read_config(config_file, user: Optional[str] = None):
 
     config_args['ssh_keyfile'] = config.get('server', 'ssh_keyfile', fallback='').strip() or None
 
-    # Empty values (as in the example config) count as false
-    for key in ['remote_sudo', 'numeric_ids']:
-        if config.get('server', key, fallback='').strip() == '':
-            config_args[key] = False
-        else:
-            config_args[key] = config.getboolean('server', key)
+    config_args['remote_sudo'] = _get_bool(config, 'remote_sudo')
+    config_args['numeric_ids'] = _get_bool(config, 'numeric_ids')
 
     return config_args