refactor: throw PushNotificationNotSupportedError instead of a generic one (#903)

See https://a2a-protocol.org/latest/specification/#332-error-handling.

Author: ishymko

src/a2a/server/request_handlers/default_request_handler.py

@@ -49,6 +49,7 @@
 from a2a.utils.errors import (
     InternalError,
     InvalidParamsError,
+    PushNotificationNotSupportedError,
     TaskNotCancelableError,
     TaskNotFoundError,
     UnsupportedOperationError,
@@ -493,7 +494,7 @@ async def on_create_task_push_notification_config(
         Requires a `PushNotifier` to be configured.
         """
         if not self._push_config_store:
-            raise UnsupportedOperationError
+            raise PushNotificationNotSupportedError
 
         task_id = params.task_id
         task: Task | None = await self.task_store.get(task_id, context)
@@ -519,7 +520,7 @@ async def on_get_task_push_notification_config(
         Requires a `PushConfigStore` to be configured.
         """
         if not self._push_config_store:
-            raise UnsupportedOperationError
+            raise PushNotificationNotSupportedError
 
         task_id = params.task_id
         config_id = params.id
@@ -594,7 +595,7 @@ async def on_list_task_push_notification_configs(
         Requires a `PushConfigStore` to be configured.
         """
         if not self._push_config_store:
-            raise UnsupportedOperationError
+            raise PushNotificationNotSupportedError
 
         task_id = params.task_id
         task: Task | None = await self.task_store.get(task_id, context)
@@ -620,7 +621,7 @@ async def on_delete_task_push_notification_config(
         Requires a `PushConfigStore` to be configured.
         """
         if not self._push_config_store:
-            raise UnsupportedOperationError
+            raise PushNotificationNotSupportedError
 
         task_id = params.task_id
         config_id = params.id

tests/server/request_handlers/test_default_request_handler.py

@@ -38,6 +38,7 @@
 from a2a.types import (
     InternalError,
     InvalidParamsError,
+    PushNotificationNotSupportedError,
     TaskNotCancelableError,
     TaskNotFoundError,
     UnsupportedOperationError,
@@ -1991,7 +1992,7 @@ async def test_set_task_push_notification_config_no_notifier():
         url='http://example.com',
     )
 
-    with pytest.raises(UnsupportedOperationError):
+    with pytest.raises(PushNotificationNotSupportedError):
         await request_handler.on_create_task_push_notification_config(
             params, create_server_call_context()
         )
@@ -2038,7 +2039,7 @@ async def test_get_task_push_notification_config_no_store():
         id='task_push_notification_config',
     )
 
-    with pytest.raises(UnsupportedOperationError):
+    with pytest.raises(PushNotificationNotSupportedError):
         await request_handler.on_get_task_push_notification_config(
             params, create_server_call_context()
         )
@@ -2269,7 +2270,7 @@ async def test_list_task_push_notification_config_no_store():
     )
     params = ListTaskPushNotificationConfigsRequest(task_id='task1')
 
-    with pytest.raises(UnsupportedOperationError):
+    with pytest.raises(PushNotificationNotSupportedError):
         await request_handler.on_list_task_push_notification_configs(
             params, create_server_call_context()
         )
@@ -2414,11 +2415,10 @@ async def test_delete_task_push_notification_config_no_store():
         task_id='task1', id='config1'
     )
 
-    with pytest.raises(UnsupportedOperationError) as exc_info:
+    with pytest.raises(PushNotificationNotSupportedError):
         await request_handler.on_delete_task_push_notification_config(
             params, create_server_call_context()
         )
-    assert isinstance(exc_info.value, UnsupportedOperationError)
 
 
 @pytest.mark.asyncio