community[patch]: changed default for VertexAIEmbeddings (#14614)

Replace this entire comment with:
- **Description:** @kurtisvg has raised a point that it's a good idea to
have a fixed version for embeddings (since otherwise a user might run a
query with one version vs a vectorstore where another version was used).
In order to avoid breaking changes, I'd suggest to give users a warning,
and make a `model_name` a required argument in 1.5 months.

libs/community/tests/integration_tests/embeddings/test_vertexai.py

@@ -5,6 +5,8 @@ pip install google-cloud-aiplatform>=1.35.0
 Your end-user credentials would be used to make the calls (make sure you've run
 `gcloud auth login` first).
 """
+import pytest
+
 from langchain_community.embeddings import VertexAIEmbeddings
 
 
@@ -15,6 +17,7 @@ def test_embedding_documents() -> None:
     assert len(output) == 1
     assert len(output[0]) == 768
     assert model.model_name == model.client._model_id
+    assert model.model_name == "textembedding-gecko@001"
 
 
 def test_embedding_query() -> None:
@@ -50,3 +53,15 @@ def test_paginated_texts() -> None:
     assert len(output) == 8
     assert len(output[0]) == 768
     assert model.model_name == model.client._model_id
+
+
+def test_warning(caplog: pytest.LogCaptureFixture) -> None:
+    _ = VertexAIEmbeddings()
+    assert len(caplog.records) == 1
+    record = caplog.records[0]
+    assert record.levelname == "WARNING"
+    expected_message = (
+        "Model_name will become a required arg for VertexAIEmbeddings starting from "
+        "Feb-01-2024. Currently the default is set to textembedding-gecko@001"
+    )
+    assert record.message == expected_message