fix: prevent panic when loadartifactstool used without artifact service

[ShammiAnand]

Fixes #283

Root Cause

internalArtifacts wrapper created with nil embedded Artifacts field. Calling List(), Load(), or Save() on nil receiver caused segfault.

Changes

• internal/toolinternal/context.go: Added nil checks to List/Load/Save methods, only create wrapper if service configured
• tool/loadartifactstool/load_artifacts_tool_test.go: Test for error when service missing
• internal/toolinternal/context_test.go: Tests for nil-safe methods

Result

Before: panic: runtime error: invalid memory address or nil pointer dereference
After: ERROR: failed to list artifacts: artifact service not configured

[gemini-code-assist]

Summary of Changes

Hello @ShammiAnand, 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 the loadartifactstool could lead to a runtime panic if it attempted to operate without a configured artifact service. The changes introduce robust checks and conditional logic to ensure that any operations on a missing service now result in a clear error message, significantly improving the stability and predictability of the tool's behavior.

Highlights

• Panic Prevention: Implemented nil checks within the internalArtifacts wrapper's List, Load, and Save methods to prevent runtime panics when the underlying artifact service is not configured.
• Conditional Initialization: Modified the NewToolContext function to conditionally initialize the internalArtifacts wrapper only if an artifact service is present, avoiding the creation of a wrapper with a nil embedded Artifacts field.
• Enhanced Test Coverage: Added new unit tests (TestInternalArtifacts_NilSafe and TestLoadArtifactsTool_ProcessRequest_NoArtifactService) to specifically verify the graceful error handling and nil-safe behavior when the artifact service is unavailable.

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[gemini-code-assist]

Code Review

This pull request effectively resolves a panic that occurred when the artifact service was not configured by introducing nil checks and conditionally creating the artifact wrapper. The inclusion of tests to cover this fix is a great addition. I've provided a couple of suggestions to further enhance the code by improving maintainability, reducing duplication, and adhering to Go's error handling best practices.

[ShammiAnand]

@baptmont can you please review this?

[verdverm]

I would think it should be possible to catch this sooner, like when the agent is configured or starts up... run a few sanity checks

Right now this feels more like a bandaid, catching at the point of failure artifact.Load/Save/List. Better than it is today, but not really solving the issue of misconfiguration until I actually try to use the artifact service

[ShammiAnand]

@verdverm

Added runner-level validation in runner.New() that:

• Walks entire agent tree checking for load_artifacts tool
• Returns error immediately if tool present but ArtifactService not configured
• Validates during runner creation (proactive) vs at tool invocation (reactive)

Before: Error at runtime when tool called
panic: runtime error: invalid memory address or nil pointer dereference

After: Error at runner creation
Failed to create runner: agent "artifact_tester" uses load_artifacts tool but ArtifactService not configured in runner

[ShammiAnand]

@verdverm can we merge it?

[verdverm]

@ShammiAnand I have no control over that, just an ADK user

[verdverm]

@ShammiAnand well, this is less likely to be merged with ~1.5M LOC being contributed

what is going on with dd35910