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/langchain_community/embeddings/vertexai.py

@@ -29,21 +29,28 @@ class VertexAIEmbeddings(_VertexAICommon, Embeddings):
     def validate_environment(cls, values: Dict) -> Dict:
         """Validates that the python package exists in environment."""
         cls._try_init_vertexai(values)
+        if values["model_name"] == "textembedding-gecko-default":
+            logger.warning(
+                "Model_name will become a required arg for VertexAIEmbeddings "
+                "starting from Feb-01-2024. Currently the default is set to "
+                "textembedding-gecko@001"
+            )
+            values["model_name"] = "textembedding-gecko@001"
         try:
             from vertexai.language_models import TextEmbeddingModel
-
-            values["client"] = TextEmbeddingModel.from_pretrained(values["model_name"])
         except ImportError:
             raise_vertex_import_error()
+        values["client"] = TextEmbeddingModel.from_pretrained(values["model_name"])
         return values
 
     def __init__(
         self,
+        # the default value would be removed after Feb-01-2024
+        model_name: str = "textembedding-gecko-default",
         project: Optional[str] = None,
         location: str = "us-central1",
         request_parallelism: int = 5,
         max_retries: int = 6,
-        model_name: str = "textembedding-gecko",
         credentials: Optional[Any] = None,
         **kwargs: Any,
     ):