Add __eq__ and __hash__ methods to State class (#928)

* Fix the ability to copy the state, now copying the state will return the same state.

* reformat

* full implement deepcopy with memo dict, add typehints

* Update aiogram/dispatcher/fsm/state.py

Co-authored-by: Oleg A. <t0rr@mail.ru>

* update tests

Co-authored-by: Oleg A. <t0rr@mail.ru>

* remove deepcopy in tests

Co-authored-by: Oleg A. <t0rr@mail.ru>

* remove deepcopy method

Co-authored-by: Oleg A. <t0rr@mail.ru>

* update changes description

Co-authored-by: Oleg A. <t0rr@mail.ru>

* update __eq__  method

Co-authored-by: Oleg A. <t0rr@mail.ru>

* add typehints, tests

* return False for not equal objects
creating FilterObject use getfullargspec that check State equality with `type` and `object` builtins, raising Error in `__eq__` method of State break this behavior

* return NotImplemented for other types

* use `!=` instead of 'not x == y' in tests

Co-authored-by: Oleg A. <t0rr@mail.ru>

CHANGES/927.bugfix.rst

@@ -0,0 +1 @@
+Fixed the ability to compare the state, now comparison to copy of the state will return `True`.

aiogram/dispatcher/fsm/state.py

@@ -54,6 +54,16 @@ class State:
             return True
         return raw_state == self.state
 
+    def __eq__(self, other: Any) -> bool:
+        if isinstance(other, self.__class__):
+            return self.state == other.state
+        if isinstance(other, str):
+            return self.state == other
+        return NotImplemented
+
+    def __hash__(self) -> int:
+        return hash(self.state)
+
 
 class StatesGroupMeta(type):
     __parent__: "Optional[Type[StatesGroup]]"

tests/test_dispatcher/test_filters/test_state.py

@@ -1,7 +1,9 @@
+from copy import copy
 from inspect import isclass
 
 import pytest
 
+from aiogram.dispatcher.event.handler import FilterObject
 from aiogram.dispatcher.filters import StateFilter
 from aiogram.dispatcher.fsm.state import State, StatesGroup
 from aiogram.types import Update
@@ -50,3 +52,23 @@ class TestStateFilter:
     async def test_filter(self, state, current_state, result):
         f = StateFilter(state=state)
         assert bool(await f(obj=Update(update_id=42), raw_state=current_state)) is result
+
+    @pytestmark
+    async def test_create_filter_from_state(self):
+        FilterObject(callback=State(state="state"))
+
+    @pytestmark
+    async def test_state_copy(self):
+        class SG(StatesGroup):
+            state = State()
+
+        assert SG.state == copy(SG.state)
+
+        assert SG.state == "SG:state"
+        assert "SG:state" == SG.state
+
+        assert State() == State()
+        assert SG.state != 1
+
+        states = {SG.state: "OK"}
+        assert states.get(copy(SG.state)) == "OK"