fix: NvidiaRanker reordered the top_k fallback to happen after validation

integrations/nvidia/src/haystack_integrations/components/rankers/nvidia/ranker.py

@@ -3,18 +3,15 @@
 # SPDX-License-Identifier: Apache-2.0
 
 import os
-import warnings
 from dataclasses import replace
 from typing import Any
 
-from haystack import Document, component, default_from_dict, default_to_dict, logging
+from haystack import Document, component, default_from_dict, default_to_dict
 from haystack.utils import Secret, deserialize_secrets_inplace
 
 from haystack_integrations.components.rankers.nvidia.truncate import RankerTruncateMode
 from haystack_integrations.utils.nvidia import DEFAULT_API_URL, Client, NimBackend, is_hosted, url_validation
 
-logger = logging.getLogger(__name__)
-
 
 @component
 class NvidiaRanker:
@@ -84,6 +81,8 @@ def __init__(
         :param timeout:
             Timeout for request calls, if not set it is inferred from the `NVIDIA_TIMEOUT` environment variable
             or set to 60 by default.
+
+        :raises ValueError: If `top_k` is not > 0.
         """
         if model is not None and not isinstance(model, str):
             msg = "Ranker expects the `model` parameter to be a string."
@@ -96,6 +95,9 @@ def __init__(
         if not isinstance(top_k, int):
             msg = "Ranker expects the `top_k` parameter to be an integer."
             raise TypeError(msg)
+        if top_k <= 0:
+            msg = f"top_k must be > 0, but got {top_k}"
+            raise ValueError(msg)
 
         # todo: detect default in non-hosted case (when api_url is provided)
         self.truncate = truncate
@@ -202,6 +204,7 @@ def run(self, query: str, documents: list[Document], top_k: int | None = None) -
         :param top_k: The number of documents to return.
 
         :raises TypeError: If the arguments are of the wrong type.
+        :raises ValueError: If `top_k` is not > 0.
 
         :returns: A dictionary containing the ranked documents.
         """
@@ -224,11 +227,10 @@ def run(self, query: str, documents: list[Document], top_k: int | None = None) -
         if len(documents) == 0:
             return {"documents": []}
 
+        if top_k is not None and top_k <= 0:
+            msg = f"top_k must be > 0, but got {top_k}"
+            raise ValueError(msg)
         top_k = top_k if top_k is not None else self.top_k
-        if top_k < 1:
-            logger.warning("top_k should be at least 1, returning nothing")
-            warnings.warn("top_k should be at least 1, returning nothing", stacklevel=2)
-            return {"documents": []}
 
         assert self.backend is not None
 

integrations/nvidia/tests/test_ranker.py

@@ -221,20 +221,27 @@ def test_nim_integration(self):
         assert len(response) == 2
         assert {response[0].content, response[1].content} == {documents[0].content, documents[1].content}
 
-    def test_top_k_warn(self, monkeypatch) -> None:
+    @pytest.mark.parametrize("top_k", [0, -1])
+    def test_top_k_init_invalid(self, monkeypatch, top_k: int) -> None:
         monkeypatch.setenv("NVIDIA_API_KEY", "fake-api-key")
+        with pytest.raises(ValueError, match=rf"top_k must be > 0, but got {top_k}"):
+            NvidiaRanker(top_k=top_k)
 
-        client = NvidiaRanker(top_k=0)
+    @pytest.mark.parametrize("top_k", [0, -1])
+    def test_top_k_run_invalid(self, monkeypatch, top_k: int) -> None:
+        monkeypatch.setenv("NVIDIA_API_KEY", "fake-api-key")
+        client = NvidiaRanker()
         client.warm_up()
-        with pytest.warns(UserWarning) as record0:
-            client.run("query", [Document(content="doc")])
-        assert "top_k should be at least 1" in str(record0[0].message)
+        with pytest.raises(ValueError, match=rf"top_k must be > 0, but got {top_k}"):
+            client.run("query", [Document(content="doc")], top_k=top_k)
 
-        client = NvidiaRanker(top_k=1)
+    def test_top_k_zero_at_run_does_not_fall_back_to_instance_top_k(self, monkeypatch) -> None:
+        # a runtime top_k=0 must raise, not silently fall back to the instance top_k
+        monkeypatch.setenv("NVIDIA_API_KEY", "fake-api-key")
+        client = NvidiaRanker(top_k=5)
         client.warm_up()
-        with pytest.warns(UserWarning) as record1:
+        with pytest.raises(ValueError, match=r"top_k must be > 0, but got 0"):
             client.run("query", [Document(content="doc")], top_k=0)
-        assert "top_k should be at least 1" in str(record1[0].message)
 
     def test_model_typeerror(self) -> None:
         with pytest.raises(TypeError) as e: