Adds ADK EventActions to A2A response

[hoonji]

Link to Issue or Description of Change

1. Link to an existing issue (if applicable):

• Closes: Add EventActions to ADK->A2A conversion #3630

Solution:
Adds Event.actions to A2A event metadata during ADK -> A2A event conversion (to allow A2A event consumers to access important info like state_delta, artifact delta, etc)

Testing Plan

pytest ./tests/unittests passes

[gemini-code-assist]

Summary of Changes

Hello @hoonji, I'm Gemini Code Assist¹! I'm currently reviewing this pull request and will post my feedback shortly. In the meantime, here's a summary to help you and other reviewers quickly get up to speed!

This pull request enhances the ADK to A2A event conversion by incorporating the Event.actions attribute into the A2A event metadata. This ensures that crucial action-related data, like state and artifact deltas, is consistently available to downstream A2A event consumers, thereby enriching the event data and supporting more comprehensive processing.

Highlights

• ADK Event Actions: The pull request adds Event.actions to the A2A event metadata during the ADK to A2A event conversion process.
• Data Accessibility: This change enables A2A event consumers to access important information such as state_delta and artifact_delta from the converted events.
• Unit Test Updates: Corresponding unit tests have been updated to reflect the inclusion of actions in the event metadata and to properly mock its behavior.

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[gemini-code-assist]

Code Review

This pull request correctly adds the Event.actions field to the A2A event metadata, ensuring that action-related information is passed along during event conversion. The changes are straightforward and include corresponding unit tests to verify the new behavior.

My review includes two main points for consideration. First, I've noted a pre-existing inconsistency with type hints related to metadata serialization, which this PR's test changes make more apparent. Second, I've pointed out that due to the current data model, empty EventActions objects will always be included in the metadata, which is inefficient. I've suggested that these be addressed in follow-up work to improve code clarity and efficiency.

[gemini-code-assist]

The actions field on an Event object is initialized with default_factory=EventActions, so event.actions will never be None. As a result, it will always be serialized and included in the metadata, even if it's an empty object representing no actions. This adds unnecessary data to every A2A event.

To make this more efficient, the actions field should only be included when it contains meaningful data. The ideal solution would be to change the definition in src/google/adk/events/event.py to actions: Optional[EventActions] = None. This would allow the existing if field_value is not None: check to correctly filter out cases where no actions are present. Since that change is outside this PR's scope, this is a good candidate for a follow-up task.

[gemini-code-assist]

This test assertion highlights a pre-existing inconsistency in event_converter.py. The _get_context_metadata function is type-hinted to return Dict[str, str], but this test correctly asserts that the value for the actions key is a dictionary, not a string.

While the A2A server expects Dict[str, Any] for metadata and this will work at runtime, the incorrect type hints are misleading and harm code maintainability.

To resolve this, the type hints in event_converter.py should be updated in a follow-up:

• _get_context_metadata's return type should be Dict[str, Any].
• _serialize_metadata_value's name, docstring, and return type hint should be changed to reflect that it can return non-string values (e.g., return type Any).

[ryanaiagent]

Hi @DeanChensj , can you please review this.