add typing to the generic IO module

felixdivo · felixdivo · commit cd3f81bedda9 · 2019-08-16T02:10:17.000+02:00
diff --git a/.travis.yml b/.travis.yml
@@ -99,7 +99,9 @@ jobs:
           can/notifier.py
           can/player.py
           can/thread_safe_bus.py
+          can/typechecking.py
           can/util.py
+          can/io/generic.py
     - stage: linter
       name: "Formatting Checks"
       python: "3.7"
diff --git a/can/io/generic.py b/can/io/generic.py
@@ -5,31 +5,34 @@
 """
 
 from abc import ABCMeta
+from typing import Optional, Union, cast
+
+from can.typechecking import FileLike, PathLike
 
 
 class BaseIOHandler(metaclass=ABCMeta):
     """A generic file handler that can be used for reading and writing.
 
     Can be used as a context manager.
 
-    :attr file-like file:
+    :attr Optional[FileLike] file:
         the file-like object that is kept internally, or None if none
         was opened
     """
 
-    def __init__(self, file, mode="rt"):
+    def __init__(self, file: Optional[Union[FileLike, PathLike]], mode: str = "rt"):
         """
         :param file: a path-like object to open a file, a file-like object
                      to be used as a file or `None` to not use a file at all
-        :param str mode: the mode that should be used to open the file, see
-                         :func:`open`, ignored if *file* is `None`
+        :param mode: the mode that should be used to open the file, see
+                     :func:`open`, ignored if *file* is `None`
         """
         if file is None or (hasattr(file, "read") and hasattr(file, "write")):
             # file is None or some file-like object
-            self.file = file
+            self.file = cast(Optional[FileLike], file)
         else:
             # file is some path-like object
-            self.file = open(file, mode)
+            self.file = open(cast(PathLike, file), mode)
 
         # for multiple inheritance
         super().__init__()
@@ -41,6 +44,7 @@ def __exit__(self, *args):
         self.stop()
 
     def stop(self):
+        """Closes the undelying file-like object and flushes it, if it was opened in write mode."""
         if self.file is not None:
             # this also implies a flush()
             self.file.close()
diff --git a/can/typechecking.py b/can/typechecking.py
@@ -1,5 +1,7 @@
 """Types for mypy type-checking
 """
+
+import os
 import typing
 
 import mypy_extensions
@@ -18,3 +20,7 @@
 
 # Used for the Abstract Base Class
 Channel = typing.Union[int, str]
+
+# Used by the IO module
+FileLike = typing.IO[typing.Any]
+PathLike = typing.Union[str, bytes, os.PathLike]
