fix: NvidiaRanker reordered the top_k fallback to happen after validation

[davidsbatista]

Related Issues

• fixes https://github.com/deepset-ai/haystack-private/issues/506

Proposed Changes:

• Added missing init-time top_k <= 0 validation.
• Breaking Change: runtime top_k <= 0 now raises ValueError instead of logging a warning and returning [].

How did you test it?

• Replaced test_top_k_warn, now raises before reaching the pytest.warns block) with:
  • test_top_k_init_invalid, test_top_k_run_invalid (both parametrized over [0, -1])
  • test_top_k_zero_at_run_does_not_fall_back_to_instance_top_k.

Checklist

• I have read the contributors guidelines and the code of conduct
• I have updated the related issue with new insights and changes
• I added unit tests and updated the docstrings
• I've used one of the conventional commit types for my PR title: fix:, feat:, build:, chore:, ci:, docs:, style:, refactor:, perf:, test:.

[github-actions]

Coverage report (nvidia)

Click to see where and how coverage changed

File	Statements	Missing	Coverage	Coverage (new stmts)	Lines missing
integrations/nvidia/src/haystack_integrations/components/rankers/nvidia
ranker.py
Project Total

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