fix: avoid writing None AWS region to environment

src/cohere/manually_maintained/cohere_aws/client.py

@@ -3,18 +3,19 @@
 import tarfile
 import tempfile
 import time
+import typing
 from typing import Any, Dict, List, Optional, Union
 
+from ..lazy_aws_deps import lazy_boto3, lazy_botocore, lazy_sagemaker
+from .chat import Chat, StreamingChat
 from .classification import Classification, Classifications
 from .embeddings import Embeddings
 from .error import CohereError
 from .generation import Generations, StreamingGenerations
-from .chat import Chat, StreamingChat
+from .mode import Mode
 from .rerank import Reranking
 from .summary import Summary
-from .mode import Mode
-import typing
-from ..lazy_aws_deps import lazy_boto3, lazy_botocore, lazy_sagemaker
+
 
 class Client:
     def __init__(
@@ -27,7 +28,7 @@ def __init__(
         `aws configure set region us-west-2` or override it with `region_name` parameter.
         """
         self.mode = mode
-        if os.environ.get('AWS_DEFAULT_REGION') is None:
+        if os.environ.get('AWS_DEFAULT_REGION') is None and aws_region is not None:
             os.environ['AWS_DEFAULT_REGION'] = aws_region
 
         if self.mode == Mode.SAGEMAKER:

tests/test_aws_client_unit.py

@@ -128,6 +128,22 @@ def test_default_mode_is_sagemaker(self) -> None:
         sig = inspect.signature(Client.__init__)
         self.assertEqual(sig.parameters["mode"].default, Mode.SAGEMAKER)
 
+    def test_missing_region_does_not_write_none_to_environment(self) -> None:
+        """No aws_region + unset AWS_DEFAULT_REGION should not crash before boto3 resolves defaults."""
+        mock_boto3 = MagicMock()
+        mock_sagemaker = MagicMock()
+
+        with patch("cohere.manually_maintained.cohere_aws.client.lazy_boto3", return_value=mock_boto3), \
+             patch("cohere.manually_maintained.cohere_aws.client.lazy_sagemaker", return_value=mock_sagemaker), \
+             patch.dict(os.environ, {}, clear=True):
+
+            from cohere.manually_maintained.cohere_aws.client import Client
+
+            Client()
+
+            self.assertNotIn("AWS_DEFAULT_REGION", os.environ)
+            self.assertEqual(mock_boto3.client.call_args_list[0].kwargs["region_name"], None)
+
 
 class TestEmbedV4Params(unittest.TestCase):
     """Fix 3: embed() should accept output_dimension and embedding_types,