fix: Add deprecation warning for camelCase alias

src/a2a/_base.py

@@ -1,3 +1,5 @@
+import warnings
+
 from typing import Any, ClassVar
 
 from pydantic import BaseModel, ConfigDict
@@ -27,7 +29,8 @@ class A2ABaseModel(BaseModel):
     serves as the foundation for future extensions or shared utilities.
 
     This implementation provides backward compatibility for camelCase aliases
-    by lazy-loading an alias map upon first use.
+    by lazy-loading an alias map upon first use. Accessing or setting
+    attributes via their camelCase alias will raise a DeprecationWarning.
     """
 
     model_config = ConfigDict(
@@ -60,14 +63,37 @@ def __setattr__(self, name: str, value: Any) -> None:
         """Allow setting attributes via their camelCase alias."""
         # Get the map and find the corresponding snake_case field name.
         field_name = type(self)._get_alias_map().get(name)  # noqa: SLF001
+
+        if field_name:
+            # An alias was used, issue a warning.
+            warnings.warn(
+                (
+                    f"Setting field '{name}' via its camelCase alias is deprecated and will be removed in version 0.3.0 "
+                    f"Use the snake_case name '{field_name}' instead."
+                ),
+                DeprecationWarning,
+                stacklevel=2,
+            )
+
         # If an alias was used, field_name will be set; otherwise, use the original name.
         super().__setattr__(field_name or name, value)
 
     def __getattr__(self, name: str) -> Any:
         """Allow getting attributes via their camelCase alias."""
         # Get the map and find the corresponding snake_case field name.
         field_name = type(self)._get_alias_map().get(name)  # noqa: SLF001
+
         if field_name:
+            # An alias was used, issue a warning.
+            warnings.warn(
+                (
+                    f"Accessing field '{name}' via its camelCase alias is deprecated and will be removed in version 0.3.0 "
+                    f"Use the snake_case name '{field_name}' instead."
+                ),
+                DeprecationWarning,
+                stacklevel=2,
+            )
+
             # If an alias was used, retrieve the actual snake_case attribute.
             return getattr(self, field_name)
 

src/a2a/server/request_handlers/default_request_handler.py

@@ -200,10 +200,10 @@ async def _setup_message_execution(
                 )
 
             task = task_manager.update_with_message(params.message, task)
-        elif params.message.taskId:
+        elif params.message.task_id:
             raise ServerError(
                 error=TaskNotFoundError(
-                    message=f'Task {params.message.taskId} was specified but does not exist'
+                    message=f'Task {params.message.task_id} was specified but does not exist'
                 )
             )
 

tests/server/request_handlers/test_default_request_handler.py

@@ -1787,7 +1787,7 @@ async def test_on_resubscribe_to_task_in_terminal_state(terminal_state):
 
 @pytest.mark.asyncio
 async def test_on_message_send_task_id_provided_but_task_not_found():
-    """Test on_message_send when taskId is provided but task doesn't exist."""
+    """Test on_message_send when task_id is provided but task doesn't exist."""
     task_id = 'nonexistent_task'
     mock_task_store = AsyncMock(spec=TaskStore)
 
@@ -1798,10 +1798,10 @@ async def test_on_message_send_task_id_provided_but_task_not_found():
     params = MessageSendParams(
         message=Message(
             role=Role.user,
-            messageId='msg_nonexistent',
+            message_id='msg_nonexistent',
             parts=[Part(root=TextPart(text='Hello'))],
-            taskId=task_id,
-            contextId='ctx1',
+            task_id=task_id,
+            context_id='ctx1',
         )
     )
 
@@ -1827,7 +1827,7 @@ async def test_on_message_send_task_id_provided_but_task_not_found():
 
 @pytest.mark.asyncio
 async def test_on_message_send_stream_task_id_provided_but_task_not_found():
-    """Test on_message_send_stream when taskId is provided but task doesn't exist."""
+    """Test on_message_send_stream when task_id is provided but task doesn't exist."""
     task_id = 'nonexistent_stream_task'
     mock_task_store = AsyncMock(spec=TaskStore)
 
@@ -1838,10 +1838,10 @@ async def test_on_message_send_stream_task_id_provided_but_task_not_found():
     params = MessageSendParams(
         message=Message(
             role=Role.user,
-            messageId='msg_nonexistent_stream',
+            message_id='msg_nonexistent_stream',
             parts=[Part(root=TextPart(text='Hello'))],
-            taskId=task_id,
-            contextId='ctx1',
+            task_id=task_id,
+            context_id='ctx1',
         )
     )
 

tests/test_types.py

@@ -1551,8 +1551,22 @@ def test_camelCase() -> None:
         supportsAuthenticatedExtendedCard=True,
     )
 
-    agent_card.supportsAuthenticatedExtendedCard = False
-
-    default_input_modes = agent_card.defaultInputModes
-    assert agent_card
+    # Test setting an attribute via camelCase alias
+    # We expect a DeprecationWarning with a specific message
+    with pytest.warns(
+        DeprecationWarning,
+        match="Setting field 'supportsAuthenticatedExtendedCard'",
+    ):
+        agent_card.supportsAuthenticatedExtendedCard = False
+
+    # Test getting an attribute via camelCase alias
+    # We expect another DeprecationWarning with a specific message
+    with pytest.warns(
+        DeprecationWarning, match="Accessing field 'defaultInputModes'"
+    ):
+        default_input_modes = agent_card.defaultInputModes
+
+    # Assert the functionality still works as expected
+    assert agent_card.supports_authenticated_extended_card is False
     assert default_input_modes == ['text']
+    assert agent_card.default_input_modes == ['text']