Address the comment of @martindurant

In case the user is not None and no password has been provided, we will
default back to the original behavior

fsspec/implementations/webhdfs.py

@@ -109,13 +109,18 @@ def __init__(
                 )
             self.pars["delegation"] = token
         self.user = user
+
         if password is not None:
             if self.user is None:
                 raise ValueError(
                     "If passing a password, the user must also be"
                     "set in order to set up the basic-auth"
                 )
             self.password = password
+        else:
+            if user is not None:
+                self.pars["user.name"] = user
+
         if proxy_to is not None:
             self.pars["doas"] = proxy_to
         if kerberos and user is not None: