*: Fix all typing hint related errors

- Try to mark class variables in component classes.

- Leave typing hints generic, such as 'list' and 'dict' where content is usually
not filled, too complex, or context is unimportant.

- backups: Handle failure for tarfile extraction so that methods are not called
on potentially None valued variables.

- backups: Prevent potentially passing a keyword argument twice.

- dynamicdns: Deal properly with outcome of urlparsing.

- ejabberd: Deal with failed regex match

- email: Fix a mypy compliant when iterating a filtered list.

- tor: Don't reuse variables for different typed values.

- tor: Don't reuse variables for different typed values.

- operation: Return None explicitly.

- operation: Ensure that keyword argument is not repeated.

Tests:

- Where only typing hints were modified and no syntax error came up, additional
testing was not done.

- `mypy --ignore-missing-imports .` run successfully.

- Generate developer documentation.

- Service runs without errors upon start up.

- backups: Listing and restoring specific apps from a backup works.

- backups: Mounting a remote backup repository works.

- NOT TESTED: dynamicdns: Migrating from old style configuration works.

- ejabberd: Verify that setting coturn configuration works.

- email: Test that showing configuration from postfix works.

- tor: Orport value is properly shown.

- transmission: Configuration values are properly set.

- users: Running unit tests as root works.

- operation: Operation status messages are show properly during app install.

- ./setup.py install runs

Signed-off-by: Sunil Mohan Adapa <sunil@medhas.org>
Reviewed-by: James Valleroy <jvalleroy@mailbox.org>

doc/dev/conf.py

@@ -111,7 +111,7 @@ htmlhelp_basename = 'FreedomBoxdoc'
 
 # -- Options for LaTeX output ------------------------------------------------
 
-latex_elements = {
+latex_elements: dict = {
     # The paper size ('letterpaper' or 'a4paper').
     #
     # 'papersize': 'letterpaper',

plinth/app.py

@@ -7,6 +7,7 @@ import collections
 import enum
 import inspect
 import logging
+from typing import ClassVar
 
 from plinth import cfg
 from plinth.signals import post_app_loading
@@ -39,14 +40,15 @@ class App:
 
     """
 
-    app_id = None
+    app_id: str | None = None
 
-    can_be_disabled = True
+    can_be_disabled: bool = True
 
-    locked = False  # Whether user interaction with the app is allowed.
+    locked: bool = False  # Whether user interaction with the app is allowed.
     # XXX: Lockdown the application UI by implementing a middleware
 
-    _all_apps = collections.OrderedDict()
+    _all_apps: ClassVar[collections.OrderedDict[
+        str, 'App']] = collections.OrderedDict()
 
     class SetupState(enum.Enum):
         """Various states of app being setup."""

plinth/frontpage.py

@@ -4,6 +4,7 @@
 import json
 import logging
 import pathlib
+from typing import ClassVar
 
 from plinth import app, cfg
 from plinth.modules.users import privileged as users_privileged
@@ -14,7 +15,7 @@ logger = logging.getLogger(__name__)
 class Shortcut(app.FollowerComponent):
     """An application component for handling shortcuts."""
 
-    _all_shortcuts = {}
+    _all_shortcuts: ClassVar[dict[str, 'Shortcut']] = {}
 
     def __init__(self, component_id, name, short_description=None, icon=None,
                  url=None, description=None, manual_page=None,

plinth/menu.py

@@ -1,5 +1,7 @@
 # SPDX-License-Identifier: AGPL-3.0-or-later
 
+from typing import ClassVar
+
 from django.urls import reverse_lazy
 
 from plinth import app
@@ -8,7 +10,7 @@ from plinth import app
 class Menu(app.FollowerComponent):
     """Component to manage a single menu item."""
 
-    _all_menus = set()
+    _all_menus: ClassVar[set['Menu']] = set()
 
     def __init__(self, component_id, name=None, short_description=None,
                  icon=None, url_name=None, url_args=None, url_kwargs=None,

plinth/migrations/0001_initial.py

@@ -17,7 +17,7 @@ class Migration(migrations.Migration):
 
     initial = True
 
-    dependencies = []
+    dependencies: list = []
 
     operations = [
         migrations.CreateModel(

plinth/modules/apache/urls.py

@@ -3,4 +3,4 @@
 URLs for the Apache module.
 """
 
-urlpatterns = []
+urlpatterns: list = []

plinth/modules/avahi/manifest.py

@@ -7,4 +7,4 @@ Application manifest for avahi.
 # /etc/avahi/services. Currently, we don't intend to make that customizable.
 # There is no necessity for backup and restore. This manifest will ensure that
 # avahi enable/disable setting is preserved.
-backup = {}
+backup: dict = {}

plinth/modules/backups/manifest.py

@@ -6,4 +6,4 @@ Application manifest for backups.
 # Currently, backup application does not have any settings. However, settings
 # such as scheduler settings, backup location, secrets to connect to remove
 # servers need to be backed up.
-backup = {}
+backup: dict = {}

plinth/modules/backups/privileged.py

@@ -31,7 +31,7 @@ def mount(mountpoint: str, remote_path: str, ssh_keyfile: Optional[str] = None,
     except AlreadyMountedError:
         return
 
-    kwargs = {}
+    input_ = None
     # the shell would expand ~/ to the local home directory
     remote_path = remote_path.replace('~/', '').replace('~', '')
     # 'reconnect', 'ServerAliveInternal' and 'ServerAliveCountMax' allow the
@@ -55,9 +55,9 @@ def mount(mountpoint: str, remote_path: str, ssh_keyfile: Optional[str] = None,
         if not password:
             raise ValueError('mount requires either a password or ssh_keyfile')
         cmd += ['-o', 'password_stdin']
-        kwargs['input'] = password.encode()
+        input_ = password.encode()
 
-    subprocess.run(cmd, check=True, timeout=TIMEOUT, **kwargs)
+    subprocess.run(cmd, check=True, timeout=TIMEOUT, input=input_)
 
 
 @privileged
@@ -266,7 +266,12 @@ def get_exported_archive_apps(path: str) -> list[str]:
         for name in filenames:
             if 'var/lib/plinth/backups-manifests/' in name \
                and name.endswith('.json'):
-                manifest_data = tar_handle.extractfile(name).read()
+                file_handle = tar_handle.extractfile(name)
+                if not file_handle:
+                    raise RuntimeError(
+                        'Unable to extract app manifest from backup file.')
+
+                manifest_data = file_handle.read()
                 manifest = json.loads(manifest_data)
                 break
 

plinth/modules/backups/repository.py

@@ -72,9 +72,9 @@ KNOWN_ERRORS = [
 
 class BaseBorgRepository(abc.ABC):
     """Base class for all kinds of Borg repositories."""
-    flags = {}
+    flags: dict[str, bool] = {}
     is_mounted = True
-    known_credentials = []
+    known_credentials: list[str] = []
 
     def __init__(self, path, credentials=None, uuid=None, schedule=None,
                  **kwargs):

plinth/modules/cockpit/manifest.py

@@ -17,4 +17,4 @@ clients = [{
 # triggered on every Plinth domain change (and cockpit application install) and
 # will set the value of allowed domains correctly. This is the only key the is
 # customized in cockpit.conf.
-backup = {}
+backup: dict = {}

plinth/modules/coturn/components.py

@@ -2,8 +2,6 @@
 """App component for other apps to manage their STUN/TURN server configuration.
 """
 
-from __future__ import annotations  # Can be removed in Python 3.10
-
 import base64
 import hashlib
 import hmac
@@ -11,6 +9,7 @@ import json
 import re
 from dataclasses import dataclass, field
 from time import time
+from typing import ClassVar, Iterable
 
 from plinth import app
 
@@ -36,9 +35,9 @@ class TurnConfiguration:
     that must be used by a STUN/TURN client after advice from the server.
 
     """
-    domain: str = None
+    domain: str | None = None
     uris: list[str] = field(default_factory=list)
-    shared_secret: str = None
+    shared_secret: str | None = None
 
     def __post_init__(self):
         """Generate URIs after object initialization if necessary."""
@@ -76,8 +75,8 @@ class UserTurnConfiguration(TurnConfiguration):
     time.
 
     """
-    username: str = None
-    credential: str = None
+    username: str | None = None
+    credential: str | None = None
 
     def to_json(self) -> str:
         """Return a JSON representation of the configuration."""
@@ -102,7 +101,7 @@ class TurnConsumer(app.FollowerComponent):
 
     """
 
-    _all = {}
+    _all: ClassVar[dict[str, 'TurnConsumer']] = {}
 
     def __init__(self, component_id):
         """Initialize the component.
@@ -115,7 +114,7 @@ class TurnConsumer(app.FollowerComponent):
         self._all[component_id] = self
 
     @classmethod
-    def list(cls) -> list[TurnConsumer]:  # noqa
+    def list(cls) -> Iterable['TurnConsumer']:
         """Return a list of all Coturn components."""
         return cls._all.values()
 

plinth/modules/diagnostics/manifest.py

@@ -3,4 +3,4 @@
 Application manifest for diagnostics.
 """
 
-backup = {}
+backup: dict = {}

plinth/modules/dynamicdns/privileged.py

@@ -3,6 +3,7 @@
 
 import pathlib
 import urllib
+from typing import Any
 
 from plinth.actions import privileged
 
@@ -30,7 +31,7 @@ def _read_configuration(path, separator='='):
 
 
 @privileged
-def export_config() -> dict[str, object]:
+def export_config() -> dict[str, bool | dict[str, dict[str, str | None]]]:
     """Return the old ez-ipupdate configuration in JSON format."""
     input_config = {}
     if _active_config.exists():
@@ -68,12 +69,12 @@ def export_config() -> dict[str, object]:
         update_url = domain['update_url']
         try:
             server = urllib.parse.urlparse(update_url).netloc
-            service_types = {
+            service_types: dict[str, str] = {
                 'dynupdate.noip.com': 'noip.com',
                 'dynupdate.no-ip.com': 'noip.com',
                 'freedns.afraid.org': 'freedns.afraid.org'
             }
-            domain['service_type'] = service_types.get(server, 'other')
+            domain['service_type'] = service_types.get(str(server), 'other')
         except ValueError:
             pass
 
@@ -86,7 +87,7 @@ def export_config() -> dict[str, object]:
                               and _active_config.exists()):
         enabled = True
 
-    output_config = {'enabled': enabled, 'domains': {}}
+    output_config: dict[str, Any] = {'enabled': enabled, 'domains': {}}
     if domain['domain']:
         output_config['domains'][domain['domain']] = domain
 

plinth/modules/ejabberd/privileged.py

@@ -28,7 +28,7 @@ MOD_IRC_DEPRECATED_VERSION = Version('18.06')
 
 yaml = YAML()
 yaml.allow_duplicate_keys = True
-yaml.preserve_quotes = True
+yaml.preserve_quotes = True  # type: ignore [assignment]
 
 TURN_URI_REGEX = r'(stun|turn):(.*):([0-9]{4})\?transport=(tcp|udp)'
 
@@ -286,7 +286,11 @@ def mam(command: str) -> Optional[bool]:
 def _generate_service(uri: str) -> dict:
     """Generate ejabberd mod_stun_disco service config from Coturn URI."""
     pattern = re.compile(TURN_URI_REGEX)
-    typ, domain, port, transport = pattern.match(uri).groups()
+    match = pattern.match(uri)
+    if not match:
+        raise ValueError('URL does not match TURN URI')
+
+    typ, domain, port, transport = match.groups()
     return {
         "host": domain,
         "port": int(port),

plinth/modules/email/postfix.py

@@ -23,7 +23,7 @@ class Service:  # NOQA, pylint: disable=too-many-instance-attributes
     wakeup: str
     maxproc: str
     command: str
-    options: str
+    options: dict[str, str]
 
     def __str__(self) -> str:
         parts = [
@@ -49,7 +49,8 @@ def get_config(keys: list) -> dict:
 
     output = _run(args)
     result = {}
-    for line in filter(None, output.split('\n')):
+    lines: list[str] = list(filter(None, output.split('\n')))
+    for line in lines:
         key, sep, value = line.partition('=')
         if not sep:
             raise ValueError('Invalid output detected')

plinth/modules/email/privileged/postfix.py

@@ -32,7 +32,7 @@ default_config = {
         ])
 }
 
-submission_options = {
+submission_options: dict[str, str] = {
     'syslog_name': 'postfix/submission',
     'smtpd_tls_security_level': 'encrypt',
     'smtpd_client_restrictions': 'permit_sasl_authenticated,reject',
@@ -43,7 +43,7 @@ submission_service = postconf.Service(service='submission', type_='inet',
                                       wakeup='-', maxproc='-', command='smtpd',
                                       options=submission_options)
 
-smtps_options = {
+smtps_options: dict[str, str] = {
     'syslog_name': 'postfix/smtps',
     'smtpd_tls_wrappermode': 'yes',
     'smtpd_sasl_auth_enable': 'yes',

plinth/modules/firewall/__init__.py

@@ -27,7 +27,7 @@ _description = [
           'security threat from the Internet.'), box_name=cfg.box_name)
 ]
 
-_port_details = {}
+_port_details: dict[str, list[str]] = {}
 
 logger = logging.getLogger(__name__)
 

plinth/modules/firewall/components.py

@@ -5,6 +5,7 @@ App component for other apps to use firewall functionality.
 
 import logging
 import re
+from typing import ClassVar
 
 from django.utils.text import format_lazy
 from django.utils.translation import gettext_lazy as _
@@ -18,7 +19,7 @@ logger = logging.getLogger(__name__)
 class Firewall(app.FollowerComponent):
     """Component to open/close firewall ports for an app."""
 
-    _all_firewall_components = {}
+    _all_firewall_components: ClassVar[dict[str, 'Firewall']] = {}
 
     def __init__(self, component_id, name=None, ports=None, is_external=False):
         """Initialize the firewall component."""

plinth/modules/firewall/manifest.py

@@ -3,4 +3,4 @@
 Application manifest for firewall.
 """
 
-backup = {}
+backup: dict = {}

plinth/modules/janus/manifest.py

@@ -11,4 +11,4 @@ clients = [{
     }]
 }]
 
-backup = {}
+backup: dict = {}

plinth/modules/jsxc/manifest.py

@@ -11,4 +11,4 @@ clients = [{
     }]
 }]
 
-backup = {}
+backup: dict = {}

plinth/modules/letsencrypt/components.py

@@ -4,6 +4,7 @@
 import logging
 import pathlib
 import threading
+from typing import ClassVar
 
 from plinth import app
 from plinth.modules.names.components import DomainName
@@ -38,7 +39,7 @@ class LetsEncrypt(app.FollowerComponent):
 
     """
 
-    _all = {}
+    _all: ClassVar[dict[str, 'LetsEncrypt']] = {}
 
     def __init__(self, component_id, domains=None, daemons=None,
                  should_copy_certificates=False, private_key_path=None,

plinth/modules/matrixsynapse/__init__.py

@@ -3,7 +3,6 @@
 
 import logging
 import os
-from typing import List
 
 from django.urls import reverse_lazy
 from django.utils.translation import gettext_lazy as _
@@ -191,7 +190,7 @@ def get_configured_domain_name():
     return config['server_name']
 
 
-def get_turn_configuration() -> (List[str], str, bool):
+def get_turn_configuration() -> tuple[TurnConfiguration, bool]:
     """Return TurnConfiguration if setup else empty."""
     for file_path, managed in ((privileged.OVERRIDDEN_TURN_CONF_PATH, False),
                                (privileged.TURN_CONF_PATH, True)):

plinth/modules/names/components.py

@@ -3,6 +3,8 @@
 App component to introduce a new domain type.
 """
 
+from typing import ClassVar
+
 from django.utils.translation import gettext_lazy as _
 
 from plinth import app
@@ -39,7 +41,7 @@ class DomainType(app.FollowerComponent):
 
     """
 
-    _all = {}
+    _all: ClassVar[dict[str, 'DomainType']] = {}
 
     def __init__(self, component_id, display_name, configuration_url,
                  can_have_certificate=True):
@@ -90,7 +92,7 @@ class DomainName(app.FollowerComponent):
     primary reason for making a domain name available as a component.
 
     """
-    _all = {}
+    _all: ClassVar[dict[str, 'DomainName']] = {}
 
     def __init__(self, component_id, name, domain_type, services):
         """Initialize a domain name.

plinth/modules/names/manifest.py

@@ -3,4 +3,4 @@
 Application manifest for names.
 """
 
-backup = {}
+backup: dict = {}

plinth/modules/pagekite/privileged.py

@@ -2,7 +2,6 @@
 """Configure PageKite."""
 
 import os
-from typing import Union
 
 import augeas
 
@@ -118,7 +117,7 @@ def set_config(frontend: str, kite_name: str, kite_secret: str):
 
 
 @privileged
-def remove_service(service: dict[str, Union[str, bool]]):
+def remove_service(service: dict[str, str]):
     """Search and remove the service(s) that match all given parameters."""
     aug = _augeas_load()
     service = utils.load_service(service)
@@ -171,7 +170,7 @@ def _add_service(aug, service):
 
 
 @privileged
-def add_service(service: dict[str, Union[str, bool]]):
+def add_service(service: dict[str, str]):
     """Add one service."""
     aug = _augeas_load()
     service = utils.load_service(service)

plinth/modules/performance/manifest.py

@@ -13,4 +13,4 @@ clients = [{
     }]
 }]
 
-backup = {}
+backup: dict = {}

plinth/modules/power/manifest.py

@@ -3,4 +3,4 @@
 Application manifest for power.
 """
 
-backup = {}
+backup: dict = {}

plinth/modules/privoxy/manifest.py

@@ -3,4 +3,4 @@
 Application manifest for privoxy.
 """
 
-backup = {}
+backup: dict = {}

plinth/modules/storage/manifest.py

@@ -3,4 +3,4 @@
 Application manifest for storage.
 """
 
-backup = {}
+backup: dict = {}

plinth/modules/storage/udisks2.py

@@ -14,7 +14,7 @@ gio = import_from_gi('Gio', '2.0')
 
 _DBUS_NAME = 'org.freedesktop.UDisks2'
 
-_INTERFACES = {
+_INTERFACES: dict[str, str] = {
     'Ata': 'org.freedesktop.UDisks2.Drive.Ata',
     'Block': 'org.freedesktop.UDisks2.Block',
     'Drive': 'org.freedesktop.UDisks2.Drive',
@@ -28,14 +28,14 @@ _INTERFACES = {
     'UDisks2': 'org.freedesktop.UDisks2',
 }
 
-_OBJECTS = {
+_OBJECTS: dict[str, str] = {
     'drives': '/org/freedesktop/UDisks2/drives/',
     'jobs': '/org/freedesktop/UDisks2/jobs/',
     'Manager': '/org/freedesktop/UDisks2/Manager',
     'UDisks2': '/org/freedesktop/UDisks2',
 }
 
-_ERRORS = {
+_ERRORS: dict[str, str] = {
     'AlreadyMounted': 'org.freedesktop.UDisks2.Error.AlreadyMounted',
     'Failed': 'org.freedesktop.UDisks2.Error.Failed',
 }
@@ -54,8 +54,8 @@ def _get_dbus_proxy(object_, interface):
 
 class Proxy:
     """Base methods for abstraction over UDisks2 DBus proxy objects."""
-    interface = None
-    properties = {}
+    interface: str | None = None
+    properties: dict[str, tuple[str, str]] = {}
 
     def __init__(self, object_path):
         """Return an object instance."""

plinth/modules/tor/privileged.py

@@ -254,8 +254,8 @@ def _get_ports() -> dict[str, str]:
 
 def _get_orport() -> str:
     """Return the ORPort by querying running instance."""
-    cookie = open(TOR_AUTH_COOKIE, 'rb').read()
-    cookie = codecs.encode(cookie, 'hex').decode()
+    cookie_bytes = open(TOR_AUTH_COOKIE, 'rb').read()
+    cookie = codecs.encode(cookie_bytes, 'hex').decode()
 
     commands = '''AUTHENTICATE {cookie}
 GETINFO net/listeners/or
@@ -270,6 +270,9 @@ QUIT
 
     line = response.split(b'\r\n')[1].decode()
     matches = re.match(r'.*=".+:(\d+)"', line)
+    if not matches:
+        raise ValueError('Invalid orport value returned by Tor')
+
     return matches.group(1)
 
 

plinth/modules/transmission/privileged.py

@@ -22,12 +22,13 @@ def get_configuration() -> dict[str, str]:
 @privileged
 def merge_configuration(configuration: dict[str, Union[str, bool]]):
     """Merge given JSON configuration with existing configuration."""
-    current_configuration = _transmission_config.read_bytes()
-    current_configuration = json.loads(current_configuration)
+    current_configuration_bytes = _transmission_config.read_bytes()
+    current_configuration = json.loads(current_configuration_bytes)
 
     new_configuration = current_configuration
     new_configuration.update(configuration)
-    new_configuration = json.dumps(new_configuration, indent=4, sort_keys=True)
+    new_configuration_bytes = json.dumps(new_configuration, indent=4,
+                                         sort_keys=True)
 
-    _transmission_config.write_text(new_configuration, encoding='utf-8')
+    _transmission_config.write_text(new_configuration_bytes, encoding='utf-8')
     action_utils.service_reload('transmission-daemon')

plinth/modules/users/components.py

@@ -4,6 +4,7 @@ App component to manage users and groups.
 """
 
 import itertools
+from typing import ClassVar
 
 from plinth import app
 
@@ -12,7 +13,7 @@ class UsersAndGroups(app.FollowerComponent):
     """Component to manage users and groups of an app."""
 
     # Class variable to hold a list of user groups for apps
-    _all_components = set()
+    _all_components: ClassVar[set['UsersAndGroups']] = set()
 
     def __init__(self, component_id, reserved_usernames=[], groups={}):
         """Store reserved_usernames and groups of the app.

plinth/modules/users/tests/test_privileged.py

@@ -16,11 +16,6 @@ from plinth import action_utils
 from plinth.modules.users import privileged
 from plinth.tests import config as test_config
 
-pytestmark = pytest.mark.usefixtures('mock_privileged')
-privileged_modules_to_mock = [
-    'plinth.modules.users.privileged', 'plinth.modules.security.privileged'
-]
-
 _cleanup_users = None
 _cleanup_groups = None
 
@@ -39,10 +34,13 @@ def _is_ldap_set_up():
         return False
 
 
-pytestmark = [
-    pytest.mark.usefixtures('needs_root', 'load_cfg'),
+pytestmark: list[pytest.MarkDecorator] = [
+    pytest.mark.usefixtures('needs_root', 'load_cfg', 'mock_privileged'),
     pytest.mark.skipif(not _is_ldap_set_up(), reason="LDAP is not configured")
 ]
+privileged_modules_to_mock = [
+    'plinth.modules.users.privileged', 'plinth.modules.security.privileged'
+]
 
 
 def _random_string(length=8):

plinth/modules/wireguard/privileged.py

@@ -19,7 +19,7 @@ def get_info() -> dict[str, dict]:
         if not line:
             continue
 
-        fields = [
+        fields: list = [
             field if field != '(none)' else None for field in line.split()
         ]
         interface_name = fields[0]

plinth/operation.py

@@ -89,10 +89,10 @@ class Operation:
         return self.return_value
 
     @staticmethod
-    def get_operation():
+    def get_operation() -> 'Operation':
         """Return the operation associated with this thread."""
         thread = threading.current_thread()
-        return thread._operation
+        return thread._operation  # type: ignore [attr-defined]
 
     def on_update(self, message: Optional[str] = None,
                   exception: Optional[Exception] = None):
@@ -106,7 +106,7 @@ class Operation:
         self._update_notification()
 
     @property
-    def message(self):
+    def message(self) -> str | None:
         """Return a message about status of the operation."""
         from django.utils.translation import gettext_noop
         if self._message:  # Progress has been set by the operation itself
@@ -124,6 +124,8 @@ class Operation:
         if self.state == Operation.State.COMPLETED:
             return gettext_noop('Finished: {name}')
 
+        return None
+
     @property
     def translated_message(self):
         """Return a message about status of operation after translating.
@@ -183,8 +185,8 @@ class OperationsManager:
     def new(self, *args, **kwargs):
         """Create a new operation instance and add to global list."""
         with self._lock:
-            operation = Operation(*args, **kwargs,
-                                  on_complete=self._on_operation_complete)
+            kwargs['on_complete'] = self._on_operation_complete
+            operation = Operation(*args, **kwargs)
             self._operations.append(operation)
             logger.info('%s: added', operation)
             self._schedule_next()

plinth/settings.py

@@ -124,7 +124,7 @@ LOGIN_URL = 'users:login'
 LOGIN_REDIRECT_URL = 'index'
 
 # Overridden before initialization
-MESSAGE_TAGS = {}
+MESSAGE_TAGS: dict = {}
 
 MIDDLEWARE = (
     'django.middleware.security.SecurityMiddleware',

plinth/tests/test_utils.py

@@ -92,7 +92,7 @@ class TestYAMLFileUtil:
     kv_pair = {'key': 'value'}
 
     yaml = ruamel.yaml.YAML()
-    yaml.preserve_quotes = True
+    yaml.preserve_quotes = True  # type: ignore [assignment]
 
     def test_update_empty_yaml_file(self):
         """

plinth/views.py

@@ -9,6 +9,7 @@ import urllib.parse
 
 from django.contrib import messages
 from django.core.exceptions import ImproperlyConfigured
+from django.forms import Form
 from django.http import Http404, HttpResponseBadRequest, HttpResponseRedirect
 from django.shortcuts import redirect
 from django.template.response import TemplateResponse
@@ -164,9 +165,9 @@ class AppView(FormView):
     instead of the simple appearance provided by default.
 
     """
-    form_class = None
-    app_id = None
-    template_name = 'app.html'
+    form_class: Form | None = None
+    app_id: str | None = None
+    template_name: str = 'app.html'
 
     def __init__(self, *args, **kwargs):
         """Initialize the view."""

plinth/web_server.py

@@ -7,6 +7,7 @@ import logging
 import os
 import sys
 import warnings
+from typing import ClassVar
 
 import cherrypy
 
@@ -104,7 +105,7 @@ class StaticFiles(app_module.FollowerComponent):
 
     """
 
-    _all_instances = {}
+    _all_instances: ClassVar[dict[str, 'StaticFiles']] = {}
 
     def __init__(self, component_id, directory_map=None):
         """Initialize the component.

setup.py

@@ -66,7 +66,7 @@ LOCALE_PATHS = ['plinth/locale']
 
 class DjangoCommand(Command):
     """Setup command to run a Django management command."""
-    user_options = []
+    user_options: list = []
 
     def initialize_options(self):
         """Declare the options for this command."""