Add warning when auth_level is used.

This parameter is no longer documented, but is probably still in use
by some codebases. It does not do anything and never has. This warning
paves the way for removing it in a future version.

Author: inklesspen

endpoints/api_config.py

@@ -152,6 +152,9 @@ def _Enum(docstring, *names):
 
 AUTH_LEVEL = _Enum(_AUTH_LEVEL_DOCSTRING, 'REQUIRED', 'OPTIONAL',
                    'OPTIONAL_CONTINUE', 'NONE')
+_AUTH_LEVEL_WARNING = ("Due to a design error, auth_level has never actually been functional. "
+                       "It will likely be removed and replaced by a functioning alternative "
+                       "in a future version of the framework. Please stop using auth_level now.")
 
 
 def _GetFieldAttributes(field):
@@ -808,6 +811,8 @@ def api_class(self, resource_name=None, path=None, audiences=None,
     Returns:
       A decorator function to decorate a class that implements an API.
     """
+    if auth_level is not None:
+      _logger.warn(_AUTH_LEVEL_WARNING)
 
     def apiserving_api_decorator(api_class):
       """Decorator for ProtoRPC class that configures Google's API server.
@@ -1046,6 +1051,8 @@ class Books(remote.Service):
   Returns:
     Class decorated with api_info attribute, an instance of ApiInfo.
   """
+  if auth_level is not None:
+    _logger.warn(_AUTH_LEVEL_WARNING)
 
   return _ApiDecorator(name, version, description=description,
                        hostname=hostname, audiences=audiences, scopes=scopes,
@@ -1275,6 +1282,8 @@ def greeting_insert(request):
     TypeError: if the request_type or response_type parameters are not
       proper subclasses of messages.Message.
   """
+  if auth_level is not None:
+    _logger.warn(_AUTH_LEVEL_WARNING)
 
   # Default HTTP method if one is not specified.
   DEFAULT_HTTP_METHOD = 'POST'