KG-159: Make parts field nullable because Gemini sometimes doesn't return it

[Ololoshechkin]

Motivation and Context

Breaking Changes

---

Type of the changes

• New feature (non-breaking change which adds functionality)
• Bug fix (non-breaking change which fixes an issue)
• Breaking change (fix or feature that would cause existing functionality to change)
• Documentation update
• Tests improvement
• Refactoring

Checklist

• The pull request has a description of the proposed change
• I read the Contributing Guidelines before opening the pull request
• The pull request uses develop as the base branch
• Tests for the changes have been added
• All new and existing tests passed

Additional steps for pull requests adding a new feature

• An issue describing the proposed change exists
• The pull request includes a link to the issue
• The change was discussed and approved in the issue
• Docs have been added / updated

[aozherelyeva]

Amazing, thank you!

[github-actions]

Qodana for JVM

591 new problems were found

Inspection name	Severity	Problems
Check Kotlin and Java source code coverage	🔶 Warning	554
Missing KDoc for public API declaration	🔶 Warning	30
Vulnerable imported dependency	🔶 Warning	6
String concatenation that can be converted to string template	◽️ Notice	1

@@ Code coverage @@
+ 70% total lines covered
9325 lines analyzed, 6579 lines covered
# Calculated according to the filters of your coverage tool

☁️ View the detailed Qodana report

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[antoniibelyshev]

Thank you! I would suggest dropping a warning message in case of an empty parts (and empty content too).

AFAIU, missing parts field is not a good sign: for example, it could result in an empty list of responses, which is not a supposed behavior.

[Ololoshechkin]

@antoniibelyshev thanks! I'll add a warning.
Indeed, it's not a supposed behavior, but apparently, that's what Gemini Flash 2.5 and Pro 2.5 do from time to time (and not on all accounts). There's a thread about that -- https://discuss.ai.google.dev/t/gemini-2-5-pro-with-empty-response-text/81175/219 -- the first problem happened in April, and the last question was from 4 hour ago -- and still not fixed.

So, on our end we can only support this and put a warning