[Bug]: Object of type Role is not JSON serializable because of Enum typing of Message.Role instead of StrEnum

[thijs-hakkenberg]

What happened?

Because the Role used in Message is an enum, a strongly typed implementation like this:

from a2a.types import Message, MessageSendParams, Task

    async def send_message(self, text: str, context_id: str = None) -> Task:
        """Send a message using A2A v10 protocol"""

        context_id = context_id or str(uuid4())
        message_id = str(uuid4())

        message = Message(
            messageId=message_id,
            contextId=context_id,
            role=Role.user,
            parts=[Part(root=TextPart(text=text))],
        )

        params = MessageSendParams(message=message)

        payload = {
            "jsonrpc": "2.0",
            "id": 1,
            "method": "message/send",
            "params": params.model_dump(),
        }
        print(payload)

        response = post(self.base_url, json=payload)
        return response.json()

will fail as enum cannot be serialized (throws: TypeError: Object of type Role is not JSON serializable)

By changing a2a.types

from enum import Enum

class Role(Enum):
    """
    Message sender's role
    """

    agent = 'agent'
    user = 'user'

into

from enum import StrEnum


class Role(StrEnum):
    """
    Message sender's role
    """

    agent = 'agent'
    user = 'user'

the role can be serialized to JSON with model_dump() as Pydantic can treat it as a string. As i cannot create branches I can’t create a PR. Would strongly suggest this approach for other string based enums as well.

Workaround would be to create an anti-corruption serialization function for MessageSendParams serialization

Relevant log output

 TypeError: Object of type Role is not JSON serializable

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[kthota-g]

This is being addressed part of #134

Until the change is available in the SDK, using params.model_dump(mode='json') will serialize to JSON types.