Symfony 2.8: ResourceInterface::isFresh() is deprecated since 2.8

Question

After upgrading to Symfony to 2.8, I found a lot of deprecation warning:

The class "Symfony\Bundle\AsseticBundle\Config\AsseticResource" is performing resource checking through ResourceInterface::isFresh(), which is deprecated since 2.8 and will be removed in 3.0 (54 times)

Stack (from Symfony profiler)

BCResourceInterfaceChecker::isFresh() (called from bootstrap.php.cache at line 3061)
ResourceCheckerConfigCache::isFresh() (called from ResourceCheckerConfigCacheFactory.php at line 45)
ResourceCheckerConfigCacheFactory::cache() (called from classes.php at line 1328)
Router::getMatcher() (called from classes.php at line 1288)
Router::match() (called from classes.php at line 7170)
Router::match() (called from classes.php at line 2086)
RouterListener::onKernelRequest()
call_user_func() (called from WrappedListener.php at line 61)
WrappedListener::__invoke()
call_user_func() (called from classes.php at line 1853)
EventDispatcher::doDispatch() (called from classes.php at line 1771)
EventDispatcher::dispatch() (called from TraceableEventDispatcher.php at line 132)
TraceableEventDispatcher::dispatch() (called from bootstrap.php.cache at line 3178)
HttpKernel::handleRaw() (called from bootstrap.php.cache at line 3151)
HttpKernel::handle() (called from bootstrap.php.cache at line 3302)
ContainerAwareHttpKernel::handle() (called from bootstrap.php.cache at line 2498)
Kernel::handle() (called from app_dev.php at line 29)

for upgrade I have used:

composer.phar update symfony/symfony --with-dependencies

this is my composer.json

{
    "name": "framework/symfony",
    "license": "proprietary",
    "type": "project",
    "autoload": {
        "psr-4": {
            "": "src/"
        }
    },
    "require": {
        "php": ">=5.3.9",
        "symfony/symfony": "2.8.*",
        "doctrine/orm": "^2.4.8",
        "doctrine/doctrine-bundle": "~1.4",
        "symfony/assetic-bundle": "~2.3",
        "symfony/swiftmailer-bundle": "~2.3",
        "symfony/monolog-bundle": "~2.4",
        "sensio/distribution-bundle": "~4.0",
        "sensio/framework-extra-bundle": "^3.0.2",
        "incenteev/composer-parameter-handler": "~2.0"
    },
    "require-dev": {
        "sensio/generator-bundle": "~2.3"
    },
    "scripts": {
        "post-install-cmd": [
            "Incenteev\\ParameterHandler\\ScriptHandler::buildParameters",
            "Sensio\\Bundle\\DistributionBundle\\Composer\\ScriptHandler::buildBootstrap",
            "Sensio\\Bundle\\DistributionBundle\\Composer\\ScriptHandler::clearCache",
            "Sensio\\Bundle\\DistributionBundle\\Composer\\ScriptHandler::installAssets",
            "Sensio\\Bundle\\DistributionBundle\\Composer\\ScriptHandler::installRequirementsFile",
            "Sensio\\Bundle\\DistributionBundle\\Composer\\ScriptHandler::prepareDeploymentTarget"
        ],
        "post-update-cmd": [
            "Incenteev\\ParameterHandler\\ScriptHandler::buildParameters",
            "Sensio\\Bundle\\DistributionBundle\\Composer\\ScriptHandler::buildBootstrap",
            "Sensio\\Bundle\\DistributionBundle\\Composer\\ScriptHandler::clearCache",
            "Sensio\\Bundle\\DistributionBundle\\Composer\\ScriptHandler::installAssets",
            "Sensio\\Bundle\\DistributionBundle\\Composer\\ScriptHandler::installRequirementsFile",
            "Sensio\\Bundle\\DistributionBundle\\Composer\\ScriptHandler::prepareDeploymentTarget"
        ]
    },
    "config": {
        "bin-dir": "bin"
    },
    "extra": {
        "symfony-app-dir": "app",
        "symfony-web-dir": "web",
        "symfony-assets-install": "relative",
        "incenteev-parameters": {
            "file": "app/config/parameters.yml"
        }
    }
}

how do solve this deprecation warning?

Answer 1

Some googling found this: https://knpuniversity.com/screencast/symfony3-upgrade/fix-deprecations-in-bundles

They link to the Assetic GitHub page which claims that 2.7.1 is ready for Symfony 3. But clearly it isn't. It's that easy. Assetic just isn't symfony 3 ready so it generates a lot deprecation notices in 2.8. The merge request to fix this hasn't been merged yet.