fix(langchain): catch gRPC errors in keyword_search, add missing methods to README

- keyword_search() now returns [] instead of raising when server returns
  UNIMPLEMENTED (older server versions without TextSearch endpoint)
- Add regression test for the raising-client case
- Add keyword_search, similarity_search, and structured_schema to API table
  in langchain-coordinode README

Author: polaz

langchain-coordinode/README.md

@@ -120,7 +120,10 @@ graph = CoordinodeGraph("localhost:7080", timeout=60.0)
 | `query(query, params)` | Execute Cypher, returns `List[Dict[str, Any]]` |
 | `refresh_schema()` | Reload node/relationship schema from database |
 | `add_graph_documents(docs)` | Batch MERGE nodes + relationships from `GraphDocument` list |
+| `keyword_search(query, k, label, fuzzy, language)` | Full-text BM25 search — returns `[{"id", "score", "snippet"}, …]` |
+| `similarity_search(query_vector, k, label, property)` | Vector nearest-neighbour search — returns `[{"id", "node", "distance"}, …]` |
 | `schema` | Schema string for LLM context |
+| `structured_schema` | Structured schema dict for programmatic access |
 
 ## Related Packages
 

langchain-coordinode/langchain_coordinode/graph.py

@@ -307,13 +307,22 @@ def keyword_search(
             # Injected clients (e.g. bare coordinode-embedded LocalClient) may
             # not implement text_search — return empty rather than AttributeError.
             return []
-        results = self._client.text_search(
-            label,
-            query,
-            limit=k,
-            fuzzy=fuzzy,
-            language=language,
-        )
+        try:
+            results = self._client.text_search(
+                label,
+                query,
+                limit=k,
+                fuzzy=fuzzy,
+                language=language,
+            )
+        except Exception:
+            # Server may return UNIMPLEMENTED (feature not yet available in the
+            # deployed version) or NOT_FOUND (no text index for *label*).
+            # We catch broad Exception (rather than grpc.RpcError specifically)
+            # because langchain-coordinode does not take a hard grpc dependency.
+            # The exception is logged at DEBUG so it remains observable.
+            logger.debug("text_search() failed — returning empty list", exc_info=True)
+            return []
         # Use "id" (not "node_id") for consistency with similarity_search() return
         # format, so callers can write generic code over both methods.
         return [{"id": r.node_id, "score": r.score, "snippet": r.snippet} for r in results]

tests/unit/test_langchain_graph.py

@@ -65,6 +65,20 @@ def close(self) -> None:
         return None
 
 
+class _ClientWithRaisingTextSearch:
+    """Fake client whose text_search raises (e.g. gRPC UNIMPLEMENTED)."""
+
+    def cypher(self, query: str, params: dict | None = None) -> list[dict]:
+        return []
+
+    def text_search(self, label: str, query: str, **kwargs: Any) -> list[Any]:
+        raise RuntimeError("StatusCode.UNIMPLEMENTED")
+
+    def close(self) -> None:
+        # No-op: keeps interface parity with real CoordinodeClient.
+        return None
+
+
 # ── Tests: keyword_search ─────────────────────────────────────────────────────
 
 
@@ -150,3 +164,12 @@ def test_empty_snippet_preserved(self) -> None:
         out = graph.keyword_search("test")
 
         assert out[0]["snippet"] == ""
+
+    def test_returns_empty_when_text_search_raises(self) -> None:
+        """Returns [] when text_search raises (e.g. gRPC UNIMPLEMENTED from older server)."""
+        client = _ClientWithRaisingTextSearch()
+        graph = CoordinodeGraph(client=client)
+
+        out = graph.keyword_search("query")
+
+        assert out == []