Suppress PasswordDeleteError in ChainerBackend.delete_password

commit_msg.txt

@@ -0,0 +1,14 @@
+Suppress PasswordDeleteError in ChainerBackend.delete_password
+
+When deleting a password through ChainerBackend, if the
+highest-priority backend raises PasswordDeleteError (because it
+doesn't hold that particular password), the chainer now catches
+the error and continues to the next backend instead of
+propagating immediately.
+
+This matches the existing pattern for NotImplementedError and
+fixes the case where a password exists in a lower-priority
+backend but cannot be deleted because a higher-priority backend
+fails first.
+
+Fixes #697

keyring/backends/chainer.py

@@ -5,6 +5,7 @@
 
 from .. import backend
 from ..compat import properties
+from ..errors import PasswordDeleteError
 from . import fail
 
 
@@ -61,7 +62,7 @@ def delete_password(self, service, username):
         for keyring in self.backends:
             try:
                 return keyring.delete_password(service, username)
-            except NotImplementedError:
+            except (NotImplementedError, PasswordDeleteError):
                 pass
 
     def get_credential(self, service, username):

tests/backends/test_chainer.py

@@ -2,6 +2,7 @@
 
 import keyring.backends.chainer
 from keyring import backend
+from keyring.errors import PasswordDeleteError
 
 
 @pytest.fixture
@@ -16,6 +17,9 @@ def get_password(self, system, user):
             def set_password(self, system, user, password):
                 pass
 
+            def delete_password(self, system, user):
+                pass
+
         class Keyring2(backend.KeyringBackend):
             priority = 2
 
@@ -25,6 +29,9 @@ def get_password(self, system, user):
             def set_password(self, system, user, password):
                 raise NotImplementedError()
 
+            def delete_password(self, system, user):
+                raise PasswordDeleteError("Password not found")
+
         return Keyring1(), Keyring2()
 
     monkeypatch.setattr('keyring.backend.get_all_keyring', get_two)
@@ -45,3 +52,13 @@ def test_chainer_defers_to_fail(self, monkeypatch):
         assert keyring.backend.by_priority(
             keyring.backends.chainer.ChainerBackend
         ) < keyring.backend.by_priority(keyring.backends.fail.Keyring)
+
+    def test_chainer_delete_skips_missing(self, two_keyrings):
+        """
+        When a higher-priority backend raises PasswordDeleteError,
+        the chainer should fall through to the next backend.
+        """
+        chainer = keyring.backends.chainer.ChainerBackend()
+        # Should not raise even though Keyring2 (higher priority)
+        # raises PasswordDeleteError
+        chainer.delete_password('alpha', 'bravo')