allow AIMessage.content=None for tool calls

libs/ai-endpoints/langchain_nvidia_ai_endpoints/chat_models.py

@@ -378,7 +378,9 @@ def _get_payload(
                 messages.append(dict(role="user", content=msg))
             elif isinstance(msg, dict):
                 if msg.get("content", None) is None:
-                    raise ValueError(f"Message {msg} has no content")
+                    # content=None is valid for assistant messages (tool calling)
+                    if not msg.get("role") == "assistant":
+                        raise ValueError(f"Message {msg} has no content.")
                 messages.append(msg)
             else:
                 raise ValueError(f"Unknown message received: {msg} of type {type(msg)}")

libs/ai-endpoints/tests/unit_tests/test_messages.py

@@ -0,0 +1,36 @@
+import requests_mock
+from langchain_core.messages import AIMessage
+
+from langchain_nvidia_ai_endpoints import ChatNVIDIA
+
+
+def test_invoke_aimessage_content_none(requests_mock: requests_mock.Mocker) -> None:
+    requests_mock.post(
+        "https://integrate.api.nvidia.com/v1/chat/completions",
+        json={
+            "id": "mock-id",
+            "created": 1234567890,
+            "object": "chat.completion",
+            "model": "mock-model",
+            "choices": [
+                {
+                    "index": 0,
+                    "message": {"role": "assistant", "content": "WORKED"},
+                }
+            ],
+        },
+    )
+
+    empty_aimessage = AIMessage(content="EMPTY")
+    empty_aimessage.content = None  # type: ignore
+
+    llm = ChatNVIDIA()
+    response = llm.invoke([empty_aimessage])
+    request = requests_mock.request_history[0]
+    assert request.method == "POST"
+    assert request.url == "https://integrate.api.nvidia.com/v1/chat/completions"
+    message = request.json()["messages"][0]
+    assert "content" in message and message["content"] != "EMPTY"
+    assert "content" in message and message["content"] is None
+    assert isinstance(response, AIMessage)
+    assert response.content == "WORKED"