feat: Add user_id property to ReadonlyContext

[ammmr]

related: #2876

Reason for this change:

Currently, there is no direct way to access the user_id from within agent contexts, plugins, or callbacks. This limitation prevents several important use cases:

1. User-specific logging and tracing: When debugging or monitoring agent behavior, it's crucial to associate actions with specific users for better observability.
2. User-scoped operations: Plugins and callbacks often need to perform user-specific operations, such as accessing user-specific resources or applying user-level configurations.
3. Session management: The user_id is a key component of session identification, but it's not accessible through the ReadonlyContext interface, requiring workarounds to access it.

Changes made:

• Added a user_id property to the ReadonlyContext class in src/google/adk/agents/readonly_context.py
• The property exposes the user_id from the underlying invocation context as a readonly field

Impact:

This change will:

• Enable plugins and callbacks to access the current user's ID directly through the context
• Improve logging and tracing capabilities by allowing user-specific tracking
• Simplify code that needs to perform user-scoped operations without requiring access to internal implementation details
• Maintain backward compatibility as this is an additive change

Before:

• No direct way to access user_id from ReadonlyContext

After:

@property
def user_id(self) -> str:
    """The id of the user. READONLY field."""
    return self._invocation_context.user_id

This is a non-breaking change that adds a new readonly property to the existing ReadonlyContext interface.

[gemini-code-assist]

Summary of Changes

Hello @ammmr, 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 ReadonlyContext by adding a user_id property. This provides a direct and standardized way for agents, plugins, and callbacks to access the current user's identifier, which is crucial for implementing user-specific functionalities, improving logging, and streamlining session management. The change is additive and maintains backward compatibility.

Highlights

• Direct User ID Access: Introduces a user_id property to the ReadonlyContext class, enabling direct access to the user's ID from within agent contexts, plugins, and callbacks. This addresses current limitations where user_id was not easily accessible.
• Enhanced Observability and User-Scoped Operations: This change facilitates user-specific logging, tracing, and operations, improving debugging and monitoring capabilities. It also simplifies the implementation of features requiring user-level configurations or resources.
• Non-Breaking and Backward Compatible: The addition of the user_id property is an additive change, ensuring backward compatibility and a smooth integration without impacting existing functionalities.

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[adk-bot]

Response from ADK Triaging Agent

Hello @ammmr, thank you for creating this PR!

To help us review this PR, could you please create and associate a GitHub issue with this PR?

Also, could you please add a testing plan section to your PR description to talk about how you will test this change?

This information will help reviewers to review your PR more efficiently. Thanks!

[gemini-code-assist]

Code Review

This pull request introduces a user_id property to the ReadonlyContext, which is a valuable addition for user-specific logging and operations. The change is well-motivated and includes a corresponding unit test. My review includes a suggestion to enhance the robustness of this new property by handling cases where a user_id might not be present, which is a common scenario in user-based systems. By typing the return value as Optional[str] and expanding the test coverage, we can ensure the new API is more resilient and prevent potential runtime errors.

[Jacksunwei]

Hi @ammmr , could you resolve the conflict for this PR?

[ammmr]

@Jacksunwei

thank you for the review!
I've resolved the conflicts in this PR.

ff421df

[hangfei]

thanks. We are merging this. No further changers are required.

[adk-bot]

Thank you @ammmr for your contribution! 🎉

Your changes have been successfully imported and merged via Copybara in commit a3b4ec6.

Closing this PR as the changes are now in the main branch.