Fixes #202

Author: sobolevn

CHANGELOG.md

@@ -6,6 +6,13 @@ incremental in minor, bugfixes only are patches.
 See (0Ver)[https://0ver.org/].
 
 
+## 0.13.0
+
+### Bugfixes
+
+- Fixes that containers were not usable with `multiprocessing`
+
+
 ## 0.12.0
 
 ### Features

returns/functions.py

@@ -3,6 +3,7 @@
 from typing import Any, Callable, NoReturn, TypeVar
 
 from returns.generated.box import _box as box  # noqa: F401, WPS436
+from returns.generated.io_context import _context as io_context
 
 # Aliases:
 _FirstType = TypeVar('_FirstType')
@@ -72,7 +73,8 @@ def tap(
     """
     Allows to apply some function and return an argument, instead of a result.
 
-    Is usefull for side-effects like ``print()``, ``logger.log``, etc.
+    Is usefull for composing functions with
+    side-effects like ``print()``, ``logger.log()``, etc.
 
     .. code:: python
 

returns/io.py

@@ -86,7 +86,7 @@ def lift(
         """
         Lifts function to be wrapped in ``IO`` for better composition.
 
-        In other words, it modifies the function
+        In other words, it modifies the function's
         signature from: ``a -> b`` to: ``IO[a] -> IO[b]``
 
         This is how it should be used:

returns/primitives/container.py

@@ -27,7 +27,7 @@ def __init__(self, inner_value) -> None:
         """
         object.__setattr__(self, '_inner_value', inner_value)  # noqa: WPS609
 
-    def __setattr__(self, attr_name: str, attr_value) -> NoReturn:
+    def __setattr__(self, attr_name: str, attr_value: Any) -> NoReturn:
         """Makes inner state of the containers immutable."""
         raise ImmutableStateError()
 
@@ -42,7 +42,7 @@ def __str__(self) -> str:
             str(self._inner_value),
         )
 
-    def __eq__(self, other) -> bool:
+    def __eq__(self, other: Any) -> bool:
         """Used to compare two 'Container' objects."""
         if not isinstance(self, type(other)):
             return False
@@ -52,6 +52,14 @@ def __hash__(self) -> int:
         """Used to use this value as a key."""
         return hash(self._inner_value)
 
+    def __getstate__(self) -> Any:
+        """That's how this object will be pickled."""
+        return self._inner_value
+
+    def __setstate__(self, state: Any) -> None:
+        """Loading state from pickled data."""
+        object.__setattr__(self, '_inner_value', state)  # noqa: WPS609
+
 
 @runtime
 class Bindable(Protocol[_ValueType]):

tests/test_io/test_io_pickle.py

@@ -0,0 +1,15 @@
+# -*- coding: utf-8 -*-
+
+from returns.io import IO
+
+
+def test_io_pickle():
+    """Tests how pickle protocol works for containers."""
+    assert IO(1).__getstate__() == 1
+
+
+def test_io_pickle_restore():
+    """Ensures that object can be restored."""
+    container = IO(2)
+    container.__setstate__(1)
+    assert container == IO(1)