[issue-458] Log if the user passes a NoneType access token

src/databricks/sql/__init__.py

@@ -10,7 +10,7 @@
 
 import re
 
-from typing import TYPE_CHECKING
+from typing import TYPE_CHECKING, Optional, Union
 
 if TYPE_CHECKING:
     # Use this import purely for type annotations, a la https://mypy.readthedocs.io/en/latest/runtime_troubles.html#import-cycles
@@ -84,7 +84,32 @@ def TimestampFromTicks(ticks):
     return Timestamp(*time.localtime(ticks)[:6])
 
 
-def connect(server_hostname, http_path, access_token=None, **kwargs) -> "Connection":
+def singleton(class_):
+    instances = {}
+
+    def getinstance(*args, **kwargs):
+        if class_ not in instances:
+            instances[class_] = class_(*args, **kwargs)
+        return instances[class_]
+
+    return getinstance
+
+
+@singleton
+class DefaultNone(object):
+    """Used to represent a default value of None so that this code can distinguish between
+    the user passing None versus a default value of None being used.
+    """
+
+    pass
+
+
+def connect(
+    server_hostname,
+    http_path,
+    access_token: Optional[Union[str, DefaultNone]] = DefaultNone,
+    **kwargs
+) -> "Connection":
     from .client import Connection
 
     return Connection(server_hostname, http_path, access_token, **kwargs)

src/databricks/sql/client.py

@@ -12,7 +12,7 @@
 import decimal
 from uuid import UUID
 
-from databricks.sql import __version__
+from databricks.sql import __version__, DefaultNone
 from databricks.sql import *
 from databricks.sql.exc import (
     OperationalError,
@@ -63,7 +63,7 @@ def __init__(
         self,
         server_hostname: str,
         http_path: str,
-        access_token: Optional[str] = None,
+        access_token: Optional[Union[str, DefaultNone]] = None,
         http_headers: Optional[List[Tuple[str, str]]] = None,
         session_configuration: Optional[Dict[str, Any]] = None,
         catalog: Optional[str] = None,
@@ -204,7 +204,13 @@ def read(self) -> Optional[OAuthToken]:
         # use_cloud_fetch
         # Enable use of cloud fetch to extract large query results in parallel via cloud storage
 
-        if access_token:
+        if access_token is DefaultNone:
+            access_token = None
+        elif access_token is None:
+            logger.info(
+                "Connection access_token was passed a None value. U2M OAuth will be attempted"
+            )
+        else:
             access_token_kv = {"access_token": access_token}
             kwargs = {**kwargs, **access_token_kv}