Update typing hints for Mypy 1.1.1

Due to a bump in our Python dependencies, we now install Mypy 1.1.1
instead of 0.982. This change triggered the following errors:

* Incompatible default for argument <a> (default has type
  None, argument has type <t>):

  Mypy further explains here that PEP 484 prohibits implicit Optional,
  so we need to make these types explicit Optional.

* Unused "type: ignore" comment, use narrower [method-assign] instead of
  [assignment]:

  Mypy has specialized some of its lints, meaning that we should switch
  to the newer variants.

Also, it detected several other small inconsistencies. We fix all of
these errors in this commit.

container/dangerzone.py

@@ -30,7 +30,9 @@ TIMEOUT_PER_MB: float = 30  # (seconds)
 TIMEOUT_MIN: float = 60  # (seconds)
 
 
-async def read_stream(sr: asyncio.StreamReader, callback: Callable = None) -> bytes:
+async def read_stream(
+    sr: asyncio.StreamReader, callback: Optional[Callable] = None
+) -> bytes:
     """Consume a byte stream line-by-line.
 
     Read all lines in a stream until EOF. If a user has passed a callback, call it for
@@ -59,8 +61,8 @@ async def run_command(
     error_message: str,
     timeout_message: str,
     timeout: Optional[float],
-    stdout_callback: Callable = None,
-    stderr_callback: Callable = None,
+    stdout_callback: Optional[Callable] = None,
+    stderr_callback: Optional[Callable] = None,
 ) -> Tuple[bytes, bytes]:
     """Run a command and get its output.
 

dangerzone/args.py

@@ -105,4 +105,4 @@ def override_parser_and_check_suspicious_options(click_main: click.Command) -> N
         check_suspicious_options(args)
         return orig_parse_fn(ctx, args)
 
-    click_main.parse_args = custom_parse_fn  # type: ignore [assignment]
+    click_main.parse_args = custom_parse_fn  # type: ignore [method-assign]

dangerzone/document.py

@@ -33,8 +33,8 @@ class Document:
 
     def __init__(
         self,
-        input_filename: str = None,
-        output_filename: str = None,
+        input_filename: Optional[str] = None,
+        output_filename: Optional[str] = None,
         suffix: str = SAFE_EXTENSION,
         archive: bool = False,
     ) -> None:

dangerzone/gui/__init__.py

@@ -55,7 +55,7 @@ class Application(QtWidgets.QApplication):
 
             return self.original_event(event)
 
-        self.event = monkeypatch_event  # type: ignore [assignment]
+        self.event = monkeypatch_event  # type: ignore [method-assign]
 
 
 @click.command()

dangerzone/gui/logic.py

@@ -6,7 +6,7 @@ import shlex
 import subprocess
 import typing
 from pathlib import Path
-from typing import Dict
+from typing import Dict, Optional
 
 from colorama import Fore
 
@@ -129,7 +129,7 @@ class Alert(QtWidgets.QDialog):
         message: str,
         ok_text: str = "Ok",
         has_cancel: bool = True,
-        extra_button_text: str = None,
+        extra_button_text: Optional[str] = None,
     ) -> None:
         super(Alert, self).__init__()
         self.dangerzone = dangerzone

dangerzone/gui/main_window.py

@@ -665,7 +665,7 @@ class ConvertTask(QtCore.QObject):
         self,
         dangerzone: DangerzoneGui,
         document: Document,
-        ocr_lang: str = None,
+        ocr_lang: Optional[str] = None,
     ) -> None:
         super(ConvertTask, self).__init__()
         self.document = document

dangerzone/isolation_provider/dummy.py

@@ -28,7 +28,7 @@ class Dummy(IsolationProvider):
             )
 
     def install(self) -> bool:
-        pass
+        return True
 
     def _convert(
         self,

tests/test_cli.py

@@ -9,7 +9,7 @@ import sys
 import tempfile
 import traceback
 from pathlib import Path
-from typing import Sequence
+from typing import Optional, Sequence
 from unittest import mock
 
 import pytest
@@ -56,7 +56,9 @@ class CLIResult(Result):
             self.print_info()
             raise
 
-    def assert_failure(self, exit_code: int = None, message: str = None) -> None:
+    def assert_failure(
+        self, exit_code: Optional[int] = None, message: Optional[str] = None
+    ) -> None:
         """Assert that the command failed.
 
         By default, check that the command has returned with an exit code
@@ -111,7 +113,7 @@ class CLIResult(Result):
 
 class TestCli(TestBase):
     def run_cli(
-        self, args: Sequence[str] | str = (), tmp_path: Path = None
+        self, args: Sequence[str] | str = (), tmp_path: Optional[Path] = None
     ) -> CLIResult:
         """Run the CLI with the provided arguments.