fix: update variable fields (#4022)

src/backend/base/langflow/services/variable/service.py

@@ -127,13 +127,15 @@ class DatabaseVariableService(VariableService, Service):
     ):
         query = select(Variable).where(Variable.id == variable_id, Variable.user_id == user_id)
         db_variable = session.exec(query).one()
+        db_variable.updated_at = datetime.now(timezone.utc)
+
+        variable.value = variable.value or ""
+        encrypted = auth_utils.encrypt_api_key(variable.value, settings_service=self.settings_service)
+        variable.value = encrypted
 
         variable_data = variable.model_dump(exclude_unset=True)
         for key, value in variable_data.items():
             setattr(db_variable, key, value)
-        db_variable.updated_at = datetime.now(timezone.utc)
-        encrypted = auth_utils.encrypt_api_key(db_variable.value, settings_service=self.settings_service)
-        variable.value = encrypted
 
         session.add(db_variable)
         session.commit()

src/backend/tests/unit/services/variable/test_service.py

@@ -155,11 +155,12 @@ def test_update_variable__ValueError(service, session):
 
 def test_update_variable_fields(service, session):
     user_id = uuid4()
+    new_name = new_value = "donkey"
     variable = service.create_variable(user_id, "old_name", "old_value", session=session)
     saved = variable.model_dump()
     variable = VariableUpdate(**saved)
-    variable.name = "new_name"
-    variable.value = "new_value"
+    variable.name = new_name
+    variable.value = new_value
     variable.default_fields = ["new_field"]
 
     result = service.update_variable_fields(
@@ -169,6 +170,8 @@ def test_update_variable_fields(service, session):
         session=session,
     )
 
+    assert result.name == new_name
+    assert result.value != new_value
     assert saved.get("id") == result.id
     assert saved.get("user_id") == result.user_id
     assert saved.get("name") != result.name