Deprecate setting a password for an empty username.

Ref #668

keyring/backend.py

@@ -10,6 +10,7 @@
 import operator
 import os
 import typing
+import warnings
 
 from jaraco.functools import once
 
@@ -100,10 +101,24 @@ def get_password(self, service: str, username: str) -> str | None:
         """Get password of the username for the service"""
         return None
 
+    def _validate_username(self, username: str) -> None:
+        """
+        Ensure the username is not empty.
+        """
+        if not username:
+            warnings.warn(
+                "Empty usernames are deprecated. See #668",
+                DeprecationWarning,
+                stacklevel=3,
+            )
+            # raise ValueError("Username cannot be empty")
+
     @abc.abstractmethod
     def set_password(self, service: str, username: str, password: str) -> None:
         """Set password for the username of the service.
 
+        Implementations should call ``._validate_username``.
+
         If the backend cannot store passwords, raise
         PasswordSetError.
         """

keyring/backends/SecretService.py

@@ -84,6 +84,7 @@ def get_password(self, service, username):
 
     def set_password(self, service, username, password):
         """Set password for the username of the service"""
+        self._validate_username(username)
         collection = self.get_preferred_collection()
         attributes = self._query(service, username, application=self.appid)
         label = f"Password for '{username}' on '{service}'"

keyring/backends/Windows.py

@@ -113,6 +113,7 @@ def _get_password(self, target):
         return DecodingCredential(res)
 
     def set_password(self, service, username, password):
+        self._validate_username(username)
         existing_pw = self._get_password(service)
         if existing_pw:
             # resave the existing password using a compound target

keyring/backends/kwallet.py

@@ -139,6 +139,7 @@ def set_password(self, service, username, password):
         if not self.connected(service):
             # the user pressed "cancel" when prompted to unlock their keyring.
             raise PasswordSetError("Cancelled by user")
+        self._validate_username(username)
         self.iface.writePassword(self.handle, service, username, password, self.appid)
 
     def delete_password(self, service, username):

keyring/backends/libsecret.py

@@ -82,6 +82,7 @@ def get_password(self, service, username):
 
     def set_password(self, service, username, password):
         """Set password for the username of the service"""
+        self._validate_username(username)
         attributes = self._query(service, username, application=self.appid)
         label = f"Password for '{username}' on '{service}'"
         try:

keyring/backends/macOS/__init__.py

@@ -42,6 +42,7 @@ def priority(cls):
 
     @warn_keychain
     def set_password(self, service, username, password):
+        self._validate_username(username)
         if username is None:
             username = ''
 

keyring/backends/null.py

@@ -17,4 +17,7 @@ def priority(cls) -> float:
     def get_password(self, service, username, password=None):
         pass
 
-    set_password = delete_password = get_password  # type: ignore
+    delete_password = get_password  # type: ignore
+
+    def set_password(self, service, username, password):
+        self._validate_username(username)

keyring/testing/backend.py

@@ -165,7 +165,8 @@ def test_credential(self):
 
     @pytest.mark.xfail("platform.system() == 'Windows'", reason="#668")
     def test_empty_username(self):
-        self.set_password('service1', '', 'password1')
+        with pytest.deprecated_call():
+            self.set_password('service1', '', 'password1')
         assert self.keyring.get_password('service1', '') == 'password1'
 
     def test_set_properties(self, monkeypatch):