Currently, there is no way of knowing whether a user intends to login with anonymous login (less likely) or whether they forget to add other required credential fields (more likely). For the clarity on error messages, and also for us to better work with this stuff I think it would be nice to add a new config option to adlfs and gcsfs (and then s3fs) regarding explicit authorization for anonymous login, called allow_anonymous_login.

We could interpret in 2 different ways, when considering a case where allow_anonymous_login is given with 2 other options account_name (mandatory), account_key (can be used with account_name to create a different authentication method);

• We could check whether there is anything available besides anonymous login, and prioritize it. If there is nothing, fallback to anonymous login
• We could disregard any other login information if the allow_anonymous_login is set to true so that it would give ability to the users to temporarily check whether their remote accepts/works with anonymous login (if that might be a use case, though I dont think so)

CC: @shcheklein @efiop @jorgeorpinel