Improve IO module typing (#1068)

* improve IO module typing

* Add missing typing_extensions dependency

* Remove the now unnesesary mypy_extensions

* Format code with black

* fix ContextManager signature in BaseIOHandler

* move type annotation of BaseIOHandler::file to actual annotation and out of the docstring

* ignore pylint false positive

Author: felixdivo

can/io/generic.py

@@ -1,24 +1,35 @@
-"""
-Contains a generic class for file IO.
-"""
+"""Contains generic base classes for file IO."""
 
 from abc import ABCMeta
-from typing import Any, Optional, cast, Union, TextIO, BinaryIO, Type
+from typing import (
+    Optional,
+    cast,
+    Iterable,
+    Union,
+    TextIO,
+    BinaryIO,
+    Type,
+    ContextManager,
+)
+from typing_extensions import Literal
+from types import TracebackType
 
 import can
 import can.typechecking
 
 
-class BaseIOHandler(metaclass=ABCMeta):
+class BaseIOHandler(ContextManager, metaclass=ABCMeta):
     """A generic file handler that can be used for reading and writing.
 
     Can be used as a context manager.
 
-    :attr Optional[FileLike] file:
-        the file-like object that is kept internally, or None if none
+    :attr file:
+        the file-like object that is kept internally, or `None` if none
         was opened
     """
 
+    file: Optional[can.typechecking.FileLike]
+
     def __init__(self, file: can.typechecking.AcceptedIOType, mode: str = "rt") -> None:
         """
         :param file: a path-like object to open a file, a file-like object
@@ -39,7 +50,12 @@ def __init__(self, file: can.typechecking.AcceptedIOType, mode: str = "rt") -> N
     def __enter__(self) -> "BaseIOHandler":
         return self
 
-    def __exit__(self, exc_type: Type, exc_val: Any, exc_tb: Any) -> Any:
+    def __exit__(
+        self,
+        exc_type: Optional[Type[BaseException]],
+        exc_val: Optional[BaseException],
+        exc_tb: Optional[TracebackType],
+    ) -> Literal[False]:
         self.stop()
         return False
 
@@ -63,5 +79,5 @@ class FileIOMessageWriter(MessageWriter, metaclass=ABCMeta):
 
 
 # pylint: disable=too-few-public-methods
-class MessageReader(BaseIOHandler, metaclass=ABCMeta):
+class MessageReader(BaseIOHandler, Iterable, metaclass=ABCMeta):
     """The base class for all readers."""

can/typechecking.py

@@ -6,10 +6,10 @@
 if typing.TYPE_CHECKING:
     import os
 
-import mypy_extensions
+import typing_extensions
 
-CanFilter = mypy_extensions.TypedDict("CanFilter", {"can_id": int, "can_mask": int})
-CanFilterExtended = mypy_extensions.TypedDict(
+CanFilter = typing_extensions.TypedDict("CanFilter", {"can_id": int, "can_mask": int})
+CanFilterExtended = typing_extensions.TypedDict(
     "CanFilterExtended", {"can_id": int, "can_mask": int, "extended": bool}
 )
 CanFilters = typing.Sequence[typing.Union[CanFilter, CanFilterExtended]]
@@ -33,7 +33,7 @@
 
 BusConfig = typing.NewType("BusConfig", typing.Dict[str, typing.Any])
 
-AutoDetectedConfig = mypy_extensions.TypedDict(
+AutoDetectedConfig = typing_extensions.TypedDict(
     "AutoDetectedConfig", {"interface": str, "channel": Channel}
 )
 

examples/simple_log_converter.py

@@ -18,7 +18,7 @@ def main():
     with can.LogReader(sys.argv[1]) as reader:
         with can.Logger(sys.argv[2]) as writer:
 
-            for msg in reader:
+            for msg in reader:  # pylint: disable=not-an-iterable
                 writer.on_message_received(msg)
 
 

setup.py

@@ -84,7 +84,7 @@
         # "setuptools",
         "wrapt~=1.10",
         'windows-curses;platform_system=="Windows" and platform_python_implementation=="CPython"',
-        "mypy_extensions>=0.4.0,<0.5.0",
+        "typing_extensions>=3.10.0.0",
         'pywin32;platform_system=="Windows" and platform_python_implementation=="CPython"',
         'msgpack~=1.0.0;platform_system!="Windows"',
     ],