fix: pass tool error to after_tool_callback

[dpasiukevich]

After functool prototype was updated to have error: func(arg) (resp, err). Now user error can be in res, err := callTool(...) and we'd need to pass this error to after_tool_callback.

Also fixes: https://github.com/google/adk-go/issues/278 (as now it will pass err.Error() from user funcs/callbacks to LLM).

[gemini-code-assist[bot]]

Summary of Changes

Hello @dpasiukevich, I'm Gemini Code Assist[^1]! 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 refines the error handling and callback mechanism within the callTool function, particularly focusing on how errors are propagated to and processed by AfterToolCallbacks. The changes ensure that any error occurring during tool execution or BeforeToolCallback is explicitly made available to AfterToolCallbacks, enabling more flexible and robust error management. This also streamlines error reporting by directly returning errors from callbacks and resolves a known issue related to passing user function errors to the LLM.

Highlights

• Enhanced Error Propagation: Errors originating from tool execution or BeforeToolCallback are now consistently passed to AfterToolCallback for centralized handling, allowing for more robust error management.
• Simplified Error Return: Error wrapping with fmt.Errorf has been removed in several places within callback invocation, allowing raw errors to be returned directly and streamlining error reporting.
• Improved AfterToolCallback Behavior: The invokeAfterToolCallbacks function now correctly returns the original tool result and error if no callback modifies them, ensuring expected fallback behavior.
• Comprehensive Testing: New unit tests have been added to validate the updated error handling and callback logic, covering various success and failure scenarios, including how callbacks handle or return errors.
• Issue Resolution: This change addresses issue https://github.com/google/adk-go/issues/278 by ensuring user function/callback errors are properly passed to the LLM.

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 :thumbsup: and :thumbsdown: 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.

[^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.