Use a descriptor to optionally store to Keyring

CURA-7180 keyring storage

cura/OAuth2/KeyringAttribute.py

@@ -0,0 +1,40 @@
+# Copyright (c) 2021 Ultimaker B.V.
+# Cura is released under the terms of the LGPLv3 or higher.
+from typing import Optional, Type
+
+import keyring
+
+from UM.Logger import Logger
+
+
+class KeyringAttribute:
+    """
+    Descriptor for attributes that need to be stored in the keyring. With Fallback behaviour to the preference cfg file
+    """
+    def __get__(self, instance: Type["BaseModel"], owner: type) -> str:
+        if self._store_secure:
+            return keyring.get_password("cura", self._keyring_name)
+        else:
+            return getattr(instance, self._name)
+
+    def __set__(self, instance: Type["BaseModel"], value: str):
+        if self._store_secure:
+            setattr(instance, self._name, None)
+            try:
+                keyring.set_password("cura", self._keyring_name, value)
+            except keyring.errors.PasswordSetError:
+                self._store_secure = False
+                setattr(instance, self._name, value)
+                Logger.logException("w", "Keyring access denied")
+        else:
+            setattr(instance, self._name, value)
+
+    def __set_name__(self, owner: type, name: str):
+        self._name = "_{}".format(name)
+        self._keyring_name = name
+        self._store_secure = False
+        try:
+            self._store_secure = keyring.backend.KeyringBackend.viable
+        except keyring.errors.KeyringError:
+            Logger.logException("w", "Could not use keyring")
+        setattr(owner, self._name, None)