Google GenAI SDK instrumentation fails to populate "finish_reasons" in the span

[michaelsafyan]

Describe your environment

Reproduces in any environment.

What happened?

The "gen_ai.response.finish_reasons" attribute is present in the span, but is empty. The "gen_ai.choice" event that is emitted shows clearly that there was a "finish_reason" present.

For example, the "finish_reason" in the "gen_ai.choice" event is "STOP", but the "gen_ai.response.finish_reasons" span attribute is [].

Steps to Reproduce

Simply execute the instrumentation such as using the example.

Expected Result

Finish reason on the span should match what was recorded in the choice event.

Actual Result

Always empty.

Additional context

I have an in-flight pull request to fix. (Please assign issue to me).

Recording the bug report, though, to provide clearer rationale for the change.

Would you like to implement a fix?

Yes

[michaelsafyan]

Pull request here:

• Ensure that the Google GenAI SDK instrumentation correctly populates "finish_reasons" on the span. #3417