ollama: add validate_model_on_init, catch more errors (#31784)

* Ensure access to local model during `ChatOllama` instantiation
(#27720). This adds a new param `validate_model_on_init` (default:
`true`)
* Catch a few more errors from the Ollama client to assist users

libs/partners/ollama/tests/unit_tests/test_chat_models.py

@@ -4,6 +4,7 @@ import json
 from collections.abc import Generator
 from contextlib import contextmanager
 from typing import Any
+from unittest.mock import patch
 
 import pytest
 from httpx import Client, Request, Response
@@ -12,6 +13,8 @@ from langchain_tests.unit_tests import ChatModelUnitTests
 
 from langchain_ollama.chat_models import ChatOllama, _parse_arguments_from_tool_call
 
+MODEL_NAME = "llama3.1"
+
 
 class TestChatOllama(ChatModelUnitTests):
     @property
@@ -49,7 +52,7 @@ def test_arbitrary_roles_accepted_in_chatmessages(
 
     llm = ChatOllama(
         base_url="http://whocares:11434",
-        model="granite3.2",
+        model=MODEL_NAME,
         verbose=True,
         format=None,
     )
@@ -64,3 +67,20 @@ def test_arbitrary_roles_accepted_in_chatmessages(
     ]
 
     llm.invoke(messages)
+
+
+@patch("langchain_ollama.chat_models.validate_model")
+def test_validate_model_on_init(mock_validate_model: Any) -> None:
+    """Test that the model is validated on initialization when requested."""
+    # Test that validate_model is called when validate_model_on_init=True
+    ChatOllama(model=MODEL_NAME, validate_model_on_init=True)
+    mock_validate_model.assert_called_once()
+    mock_validate_model.reset_mock()
+
+    # Test that validate_model is NOT called when validate_model_on_init=False
+    ChatOllama(model=MODEL_NAME, validate_model_on_init=False)
+    mock_validate_model.assert_not_called()
+
+    # Test that validate_model is NOT called by default
+    ChatOllama(model=MODEL_NAME)
+    mock_validate_model.assert_not_called()

libs/partners/ollama/tests/unit_tests/test_embeddings.py

@@ -1,8 +1,30 @@
 """Test embedding model integration."""
 
+from typing import Any
+from unittest.mock import patch
+
 from langchain_ollama.embeddings import OllamaEmbeddings
 
+MODEL_NAME = "llama3.1"
+
 
 def test_initialization() -> None:
     """Test embedding model initialization."""
     OllamaEmbeddings(model="llama3", keep_alive=1)
+
+
+@patch("langchain_ollama.embeddings.validate_model")
+def test_validate_model_on_init(mock_validate_model: Any) -> None:
+    """Test that the model is validated on initialization when requested."""
+    # Test that validate_model is called when validate_model_on_init=True
+    OllamaEmbeddings(model=MODEL_NAME, validate_model_on_init=True)
+    mock_validate_model.assert_called_once()
+    mock_validate_model.reset_mock()
+
+    # Test that validate_model is NOT called when validate_model_on_init=False
+    OllamaEmbeddings(model=MODEL_NAME, validate_model_on_init=False)
+    mock_validate_model.assert_not_called()
+
+    # Test that validate_model is NOT called by default
+    OllamaEmbeddings(model=MODEL_NAME)
+    mock_validate_model.assert_not_called()

libs/partners/ollama/tests/unit_tests/test_llms.py

@@ -1,7 +1,12 @@
 """Test Ollama Chat API wrapper."""
 
+from typing import Any
+from unittest.mock import patch
+
 from langchain_ollama import OllamaLLM
 
+MODEL_NAME = "llama3.1"
+
 
 def test_initialization() -> None:
     """Test integration initialization."""
@@ -26,3 +31,20 @@ def test_model_params() -> None:
         "ls_model_name": "llama3",
         "ls_max_tokens": 3,
     }
+
+
+@patch("langchain_ollama.llms.validate_model")
+def test_validate_model_on_init(mock_validate_model: Any) -> None:
+    """Test that the model is validated on initialization when requested."""
+    # Test that validate_model is called when validate_model_on_init=True
+    OllamaLLM(model=MODEL_NAME, validate_model_on_init=True)
+    mock_validate_model.assert_called_once()
+    mock_validate_model.reset_mock()
+
+    # Test that validate_model is NOT called when validate_model_on_init=False
+    OllamaLLM(model=MODEL_NAME, validate_model_on_init=False)
+    mock_validate_model.assert_not_called()
+
+    # Test that validate_model is NOT called by default
+    OllamaLLM(model=MODEL_NAME)
+    mock_validate_model.assert_not_called()