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Fix Deprecation Warnings from Bundles

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Once you're on 2.8, there's a new game: find and fix deprecation notices. But there's a catch! You won't hit all of your code paths at runtime. Some code paths are only executed when the cache is being built. To hit those, start by clearing the cache:

rm -rf var/cache/*

Refresh the page and click into the deprecated calls on the Web Debug Toolbar.

Deprecations come from Outside Bundles

Ok, here's the really tricky thing about deprecation notices: many of them are not your fault. Yep, a lot of notices come from all of those lazy third-party bundles you're using in your project. So to start, let's find out what outside bundles are causing problems... before we worry about fixing our stuff.

The first deprecation - about not quoting @ symbols in YAML is our fault.

Not quoting a scalar starting with '@' is deprecated since Symfony 2.8

But it's not easy to see: you need to study the stack trace. This ultimately starts with AppKernel::registerContainerConfiguration() where our configuration files are loaded.

The second is complaining about bad configuration in security.yml: that's also our fault, and we'll fix it in a minute.

But look at the third warning:

The Symfony\Component\DependencyInjection\Reference::isStrict method is deprecated since version 2.8

Look closely at the LoggerChannelPass: that's coming from MonologBundle. That's the first outside bundle that needs to be updated.

Below that, the knp_pagination Twig extension problem is obviously coming from KnpPaginatorBundle.

But before you upgrade those, go back and refresh again. This time the page pulls from the cache, and that can sometimes cause different deprecation notices to show up. A-ha!

The class "Symfony\Bundle\AsseticBundle\Config\AsseticResource" is performing resource checking through ResourceInterface::isFresh(), which is deprecated since 2.8

This deprecation warning comes from AsseticBundle: that's our third troublesome library.

Updating Bundles with Deprecations

Update these by running composer update followed by their names. Copy them from composer.json:

composer update knplabs/knp-paginator-bundle symfony/assetic-bundle symfony/monolog-bundle --with-dependencies

Notice I'm not tweaking their version constraints in composer.json. Maybe I will need to do this, but I'll take the lazy route first and hope that upgrading these to the newest version allowed by their existing constraints will be enough.

Let's see what happens!

Cool! This downloaded some patch version updates, which may have solved our problem... or maybe it didn't. Clear the cache and go refresh:

rm -rf var/cache/*

Click into the deprecations. Now the notices are down to 5 and they're coming from our code. Problem solved! But wait, refresh again. Huh, now there are 32 notices: the ones from AsseticBundle are back! The new version of AsseticBundle did not fix that problem.

The Bundle isn't Symfony 3 Ready!?

Google for AsseticBundle and go to its Github Page. The first thing to look for is a release that has Symfony 3 support. Huh, there is one that claims support: version 2.7.1. And that is the version of the library we just downloaded. Usually, this means you're fine... but clearly it's not fine: we're still getting deprecated notices! What's going on AsseticBundle!

In fact, at the time of recording, this bundle claims Symfony 3 support, but it doesn't quite have it: there's one pull request that still needs to be merged. By the time you're watching this, it'll hopefully be merged and you'll happily get the 2.7.2 version.

But I'm glad this happened: it uncovers the most difficult part of upgrading to Symfony 3. If you use a lot of outside bundles, they might not all be ready immediately when Symfony 3 is released. In fact, some might not be updated a month later. Your job is to check the repository, see if there is a Symfony 3-compatible release, and open up a friendly issue if there isn't.

For right now, until this is merged, there's nothing we can do. So let's ignore these deprecations and fix everything else.