fix: add default credential for azure (#7095) (#7891)

* fix: add default credential for azure (#7095)

* fix: fix linting error

* fix: remove redundant test

* test: skip redundant test

---------

Co-authored-by: you-n-g <you-n-g@users.noreply.github.com>

litellm/secret_managers/get_azure_ad_token_provider.py

@@ -1,5 +1,7 @@
 import os
-from typing import Callable
+from typing import Callable, Union
+
+from litellm._logging import verbose_logger
 
 
 def get_azure_ad_token_provider() -> Callable[[], str]:
@@ -14,18 +16,29 @@ def get_azure_ad_token_provider() -> Callable[[], str]:
     Returns:
         Callable that returns a temporary authentication token.
     """
-    from azure.identity import ClientSecretCredential, get_bearer_token_provider
+    from azure.identity import (
+        ClientSecretCredential,
+        DefaultAzureCredential,
+        get_bearer_token_provider,
+    )
 
     try:
-        credential = ClientSecretCredential(
+        credential: Union[ClientSecretCredential, DefaultAzureCredential] = (
+            ClientSecretCredential(
                 client_id=os.environ["AZURE_CLIENT_ID"],
                 client_secret=os.environ["AZURE_CLIENT_SECRET"],
                 tenant_id=os.environ["AZURE_TENANT_ID"],
             )
+        )
     except KeyError as e:
-        raise ValueError(
-            "Missing environment variable required by Azure AD workflow."
-        ) from e
+        verbose_logger.exception(
+            "Missing environment variable required by Azure AD workflow. "
+            "DefaultAzureCredential will be used"
+            " {}".format(str(e))
+        )
+        credential = DefaultAzureCredential()
+    except Exception:
+        raise
 
     return get_bearer_token_provider(
         credential,

tests/local_testing/test_router_client_init.py

@@ -84,6 +84,9 @@ async def test_router_init():
     )
 
 
+@pytest.mark.skip(
+    reason="This test is not relevant to the current codebase. The default Azure AD workflow is used."
+)
 @patch("litellm.secret_managers.get_azure_ad_token_provider.os")
 def test_router_init_with_neither_api_key_nor_azure_service_principal_with_secret(
     mocked_os_lib: MagicMock,