fix: only first artifact delta from multiple tool calls is being kept

[mgmcintyre]

Fixes #493

Problem

Artifact deltas were ignored when aggregating the results of multiple tool calls in mergeParallelFunctionResponseEvents, with the first non-nil ArtifactDelta winning and others discarded.

Fix

Artifact deltas are now merged using "highest-version-wins". Test cases have been added to TestMergeEventActions mirroring the coverage for state delta merging.

The current implementation in adk-python uses "last-write-wins", however "highest-version-wins" preserves more information.

Related

#449 which fixed a similar issue with state deltas.

[gemini-code-assist]

Summary of Changes

Hello @mgmcintyre, 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 resolves a critical issue where artifact deltas from parallel function responses were not being properly aggregated, resulting in incomplete data. By implementing a 'highest-version-wins' merge strategy, the system now correctly combines artifact deltas, ensuring that all relevant versioned information is preserved across multiple tool calls. This enhancement improves the robustness and data consistency of the system's event action processing.

Highlights

• Artifact Delta Merging Fix: Previously, when multiple tool calls returned artifact deltas, only the first non-nil ArtifactDelta was retained, leading to potential data loss. This PR introduces a fix to correctly merge these deltas.
• Highest-Version-Wins Strategy: The merging logic for artifact deltas now employs a 'highest-version-wins' strategy. This ensures that for any conflicting artifact entries, the one with the highest version number is preserved, maximizing data integrity.
• Comprehensive Test Coverage: New test cases have been added to TestMergeEventActions to thoroughly validate the ArtifactDelta merging functionality, mirroring the existing coverage for state delta merging and covering various merge scenarios.

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[gemini-code-assist]

Code Review

This pull request fixes a bug where artifact deltas from multiple parallel tool calls were not merged correctly, with only the first one being kept. The fix introduces a new function mergeArtifactDeltas to merge these deltas using a 'highest-version-wins' strategy, which is a good approach. The changes are well-tested with new unit tests covering various scenarios. I've found one potential issue in the new merge logic related to handling new keys with negative version numbers, and I've provided a suggestion to make it more robust.

[mgmcintyre]

/gemini review

[gemini-code-assist]

Code Review

This pull request correctly addresses a bug where artifact deltas from multiple tool calls were not being merged, causing data loss. The fix introduces a mergeArtifactDeltas function that implements a "highest-version-wins" strategy, which is a robust approach for this scenario. The new logic is well-supported by a comprehensive set of new unit tests that cover various merging cases, including overlapping and non-overlapping keys. The implementation is sound and consistent with the existing codebase. I have one minor suggestion to improve the conciseness of the new helper function.

[mgmcintyre]

/gemini review

[gemini-code-assist]

Code Review

This pull request addresses a bug where artifact deltas from multiple tool calls were not being aggregated correctly, with only the first one being preserved. The fix introduces a mergeArtifactDeltas function that merges these deltas using a 'highest-version-wins' strategy, which is a sensible approach to preserve the most recent information. The changes are well-tested with a comprehensive set of new test cases covering various merge scenarios, including overlapping and non-overlapping keys, and edge cases like nil deltas. The implementation is clean and effectively resolves the issue. Overall, this is a solid contribution that improves the correctness of parallel tool call handling.