feat: implement bidi actions and flows

[pavelgj]

RFC: #4210

Checklist (if applicable):

• PR title is following https://www.conventionalcommits.org/en/v1.0.0/
• Tested (manually, unit tested, etc.)
• Docs updated (updated docs or a docs bug required)

[gemini-code-assist]

Summary of Changes

Hello @pavelgj, 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 significantly enhances the framework by introducing comprehensive support for bi-directional actions and flows. This new capability allows for interactive, real-time communication patterns, such as chat-like interfaces, where both the client and the server-side action/flow can send and receive data asynchronously. The changes involve extending core interfaces, adding new functions for defining these bi-directional components, and ensuring robust input and initialization data validation, all backed by new test suites.

Highlights

• Bi-directional Action and Flow Support: Introduced new interfaces and functions (BidiStreamingResponse, streamBidi, defineBidiAction, bidiAction, defineBidiFlow, bidiFlow) to enable bi-directional streaming for actions and flows.
• Enhanced Type Safety and Configuration: Updated ActionRunOptions, ActionFnArg, Action, Flow, and FlowConfig with generic types for input streams and initialization data (I, Init), and added initSchema for configuration.
• Input and Initialization Data Validation: Implemented schema validation for both streaming input (inputStream) and initial configuration data (init) within bi-directional actions and flows.
• New Test Coverage: Added dedicated test files (bidi-action_test.ts, bidi-flow_test.ts) to thoroughly validate the new bi-directional streaming capabilities, including push/pull mechanisms, classic run compatibility, and data validation.

🧠 New Feature in Public Preview: You can now enable Memory to help Gemini Code Assist learn from your team's feedback. This makes future code reviews more consistent and personalized to your project's style. Click here to enable Memory in your admin console.

Using Gemini Code Assist

The full guide for Gemini Code Assist can be found on our documentation page, here are some quick tips.

Invoking Gemini

You can request assistance from Gemini at any point by creating a comment using either /gemini <command> or @gemini-code-assist <command>. Below is a summary of the supported commands on the current page.

Feature	Command	Description
Code Review	/gemini review	Performs a code review for the current pull request in its current state.
Pull Request Summary	/gemini summary	Provides a summary of the current pull request in its current state.
Comment	@gemini-code-assist	Responds in comments when explicitly tagged, both in pull request comments and review comments.
Help	/gemini help	Displays a list of available commands.

Customization

To customize Gemini Code Assist for GitHub experience, repository maintainers can create a configuration file and/or provide a custom code review style guide (such as PEP-8 for Python) by creating and adding files to a .gemini/ folder in the base of the repository. Detailed instructions can be found here.

Limitations & Feedback

Gemini Code Assist may make mistakes. Please leave feedback on any instances where its feedback is incorrect or counter productive. You can react with 👍 and 👎 on @gemini-code-assist comments. If you're interested in giving your feedback about your experience with Gemini Code Assist for Github and other Google products, sign up here.

You can also get AI-powered code generation, chat, as well as code reviews directly in the IDE at no cost with the Gemini Code Assist IDE Extension.

Footnotes

1. Review the Privacy Notices, Generative AI Prohibited Use Policy, Terms of Service, and learn how to configure Gemini Code Assist in GitHub here. Gemini can make mistakes, so double check it and use code with caution. ↩

[gemini-code-assist]

Code Review

This pull request introduces a significant and well-implemented feature: support for bidirectional streaming in actions and flows. The changes correctly extend core interfaces like Action, ActionRunOptions, and ActionFnArg to handle streaming inputs and initialization data. The new factory functions bidiAction and bidiFlow are consistent with existing patterns, and the feature is supported by a comprehensive new test suite.

My review focuses on improving type safety by correcting several incomplete or incorrect type assertions in the new implementation. These adjustments will enhance code robustness and maintainability. I've also noted a minor, potentially out-of-scope change in registry.ts and a small typing improvement for a new helper function. Overall, this is a solid contribution.