Add extensions for class-based error handler

aiogram/dispatcher/handler/error.py

@@ -7,3 +7,11 @@ class ErrorHandler(BaseHandler[Exception], ABC):
     """
     Base class for errors handlers
     """
+
+    @property
+    def exception_name(self) -> str:
+        return self.event.__class__.__name__
+
+    @property
+    def exception_message(self) -> str:
+        return str(self.event)

docs/dispatcher/class_based_handlers/error.md

@@ -13,14 +13,17 @@ class MyHandler(ErrorHandler):
     async def handle(self) -> Any:
         log.exception(
             "Cause unexpected exception %s: %s", 
-            self.event.__class__.__name__, 
-            self.event
+            self.exception_name, 
+            self.exception_message
         )
 ```
 
 ## Extension
 
-This base handler is subclass of [BaseHandler](basics.md#basehandler)
+This base handler is subclass of [BaseHandler](basics.md#basehandler) with some extensions:
+
+- `#!python3 self.exception_name` is alias for `#!python3 self.event.__class__.__name__`
+- `#!python3 self.exception_message` is alias for `#!python3 str(self.event)`
 
 ## Related pages
 

tests/test_dispatcher/test_handler/test_error.py

@@ -0,0 +1,29 @@
+from typing import Any
+
+import pytest
+
+from aiogram.api.types import (
+    CallbackQuery,
+    InlineQuery,
+    Poll,
+    PollOption,
+    ShippingAddress,
+    ShippingQuery,
+    User,
+)
+from aiogram.dispatcher.handler import ErrorHandler, PollHandler
+
+
+class TestErrorHandler:
+    @pytest.mark.asyncio
+    async def test_extensions(self):
+        event = KeyError("kaboom")
+
+        class MyHandler(ErrorHandler):
+            async def handle(self) -> Any:
+                assert self.event == event
+                assert self.exception_name == event.__class__.__name__
+                assert self.exception_message == str(event)
+                return True
+
+        assert await MyHandler(event)