Upgrading to Newer Releases
Flask itself is changing like any software is changing over time. Most of the changes are the nice kind, the kind where you don't have th change anything in your code to profit from a new release.
However every once in a while there are changes that do require some changes in your code or there are changes that make it possible for you to improve your own code quality by taking advantage of new features in Flask.
This section of the documentation enumerates all the changes in Flask from release to release and how you can change your code to have a painless updating experience.
Flask 0.5 introduces configuration support and logging as well as categories for flashing messages. All these are features that are 100% backwards compatible but you might want to take advantage of them.
The configuration support makes it easier to write any kind of application that requires some sort of configuration. (Which most likely is the case for any application out there).
If you previously had code like this:
app.debug = DEBUG app.secret_key = SECRET_KEY
You no longer have to do that, instead you can just load a configuration into the config object. How this works is outlined in :ref:`config`.
Flask now configures a logger for you with some basic and useful defaults. If you run your application in production and want to profit from automatic error logging, you might be interested in attaching a proper log handler. Also you can start logging warnings and errors into the logger when appropriately. For more information on that, read :ref:`application-errors`.
Categories for Flash Messages
Flash messages can now have categories attached. This makes it possible to render errors, warnings or regular messages differently for example. This is an opt-in feature because it requires some rethinking in the code.
Read all about that in the :ref:`message-flashing-pattern` pattern.