Fix live multi-turn: pass the resolved drug, stop did-you-mean garbage

apps/ai-service/tests/test_rerank_overview.py

@@ -0,0 +1,92 @@
+"""A free-form question about a resolved drug must not dump the whole monograph
+at the model. When a reranker is configured, the overview is reordered by
+relevance and trimmed to top-k; a bare drug name still returns everything.
+"""
+from __future__ import annotations
+
+from rag.models import EvidenceDecision, RetrievalDocument, SearchHit, SourceRef
+from rag.ports import RerankUnavailable
+from rag.service import EvidencePolicy, RetrievalService
+
+
+def _hit(i: int) -> SearchHit:
+    doc = RetrievalDocument(
+        doc_id=f"d{i}",
+        drug_id="paracetamol",
+        kind="prose",
+        text=f"section {i} text",
+        section_key=f"sec_{i}",
+        source_refs=(
+            SourceRef(physical_page=100 + i, precision="exact", printed_page=i),
+        ),
+    )
+    return SearchHit(document=doc, score=1.0)
+
+
+class _Retriever:
+    def __init__(self, n: int) -> None:
+        self._hits = [_hit(i) for i in range(n)]
+
+    def find_by_drug(self, drug_id: str) -> list[SearchHit]:
+        return list(self._hits)
+
+    def search(self, query: str, drug_id: str, limit: int) -> list[SearchHit]:  # noqa: ARG002
+        return []
+
+
+class _ParentStore:
+    def get(self, parent_id: str):  # noqa: ARG002
+        return None
+
+
+class _Reranker:
+    def __init__(self, order: list[int], fail: bool = False) -> None:
+        self._order = order
+        self._fail = fail
+        self.calls: list[str] = []
+
+    def rerank(self, query: str, documents: list[str], top_n=None):  # noqa: ARG002
+        self.calls.append(query)
+        if self._fail:
+            raise RerankUnavailable("provider down")
+        return self._order
+
+
+def _service(reranker=None, top_k=3) -> RetrievalService:
+    return RetrievalService(
+        _Retriever(8),
+        _ParentStore(),
+        EvidencePolicy(rerank_top_k=top_k),
+        section_resolver=None,
+        reranker=reranker,
+    )
+
+
+def test_a_question_reranks_the_overview_and_keeps_top_k():
+    reranker = _Reranker(order=[7, 6, 5, 4, 3, 2, 1, 0])
+    result = _service(reranker, top_k=3).retrieve(
+        "sốt cao uống được không", "paracetamol"
+    )
+
+    assert result.decision == EvidenceDecision.ANSWERABLE
+    assert reranker.calls, "reranker should run on a free-form question"
+    assert len(result.evidence) == 3
+    assert [e.matched_doc_id for e in result.evidence] == ["d7", "d6", "d5"]
+
+
+def test_a_bare_drug_name_returns_the_whole_monograph_unreranked():
+    reranker = _Reranker(order=[0])
+    result = _service(reranker).retrieve("PARACETAMOL", "paracetamol")
+
+    assert reranker.calls == [], "a bare name must not be reranked/trimmed"
+    assert len(result.evidence) == 8
+
+
+def test_rerank_outage_keeps_the_original_order():
+    reranker = _Reranker(order=[], fail=True)
+    result = _service(reranker).retrieve("sốt cao uống được không", "paracetamol")
+
+    # Fail-open: the answer survives, in book order, when rerank is unreachable.
+    assert result.decision == EvidenceDecision.ANSWERABLE
+    assert len(result.evidence) == 8
+    assert [e.matched_doc_id for e in result.evidence][:2] == ["d0", "d1"]