Fix Config subclass attribute discovery and caching

NEXT_CHANGELOG.md

@@ -11,6 +11,7 @@
 ### Bug Fixes
 
 * FilesExt no longer retries on 500 (Internal Server Error) responses. These errors now fail immediately or fallback to alternative upload methods as appropriate.
+* Fixed `Config` subclass attribute discovery and caching so inherited `ConfigAttribute` fields resolve correctly (addresses [#1069](https://github.com/databricks/databricks-sdk-py/issues/1069), [#1258](https://github.com/databricks/databricks-sdk-py/pull/1258)).
 
 ### Documentation
 

databricks/sdk/config.py

@@ -596,21 +596,29 @@ def clock(self) -> Clock:
     @classmethod
     def attributes(cls) -> Iterable[ConfigAttribute]:
         """Returns a list of Databricks SDK configuration metadata"""
-        if hasattr(cls, "_attributes"):
+        if "_attributes" in cls.__dict__:
             return cls._attributes
         if sys.version_info[1] >= 10:
             import inspect
 
-            anno = inspect.get_annotations(cls)
+            get_annotations = inspect.get_annotations
         else:
             # Python 3.7 compatibility: getting type hints require extra hop, as described in
             # "Accessing The Annotations Dict Of An Object In Python 3.9 And Older" section of
             # https://docs.python.org/3/howto/annotations.html
-            anno = cls.__dict__["__annotations__"]
-        attrs = []
-        for name, v in cls.__dict__.items():
-            if type(v) != ConfigAttribute:
+            get_annotations = lambda class_obj: class_obj.__dict__.get("__annotations__", {})
+        anno = {}
+        attrs_by_name = {}
+        for class_obj in reversed(cls.mro()):
+            if class_obj is object:
                 continue
+            anno.update(get_annotations(class_obj))
+            for name, v in class_obj.__dict__.items():
+                if type(v) != ConfigAttribute:
+                    continue
+                attrs_by_name[name] = v
+        attrs = []
+        for name, v in attrs_by_name.items():
             v.name = name
             v.transform = v._custom_transform if v._custom_transform else anno.get(name, str)
             attrs.append(v)

tests/test_core.py

@@ -276,6 +276,19 @@ def __init__(self):
         DatabricksConfig()
 
 
+def test_config_subclass_inherits_attributes(monkeypatch):
+    # Force a fresh attribute resolution path on the subclass.
+    monkeypatch.delattr(Config, "_attributes", raising=False)
+
+    class DatabricksConfig(Config):
+        pass
+
+    cfg = DatabricksConfig(host="https://abc123.azuredatabricks.net", token="x")
+
+    assert cfg.host == "https://abc123.azuredatabricks.net"
+    assert cfg.token == "x"
+
+
 def test_config_parsing_non_string_env_vars(monkeypatch):
     monkeypatch.setenv("DATABRICKS_DEBUG_TRUNCATE_BYTES", "100")
     c = Config(host="http://localhost", credentials_strategy=noop_credentials)