This PR was merged into the 3.1-dev branch. Discussion ---------- [FrameworkBundle][Serializer] Fix a deprecation triggered by the ClassMetadataFactory | Q | A | ------------- | --- | Branch? | master | Bug fix? | yes | New feature? | no | BC breaks? | no | Deprecations? | yes | Tests pass? | yes | Fixed tickets | | License | MIT Without apparent reasons, [FOSRestBundle's tests fail](https://travis-ci.org/FriendsOfSymfony/FOSRestBundle/jobs/124384888) since #18561. ``` Passing a Doctrine Cache instance as 2nd parameter of the "Symfony\Component\Serializer\Mapping\Factory\ClassMetadataFactory" constructor is deprecated. This parameter will be removed in Symfony 4.0. Use the "Symfony\Component\Serializer\Mapping\Factory\CacheClassMetadataFactory" class instead: 6x 1x in ErrorWithTemplatingFormatTest::testSerializeExceptionHtml from FOS\RestBundle\Tests\Functional 1x in SerializerErrorTest::testSerializeExceptionJson from FOS\RestBundle\Tests\Functional 1x in SerializerErrorTest::testSerializeExceptionJsonWithoutDebug from FOS\RestBundle\Tests\Functional 1x in SerializerErrorTest::testSerializeExceptionXml from FOS\RestBundle\Tests\Functional 1x in SerializerErrorTest::testSerializeInvalidFormJson from FOS\RestBundle\Tests\Functional 1x in SerializerErrorTest::testSerializeInvalidFormXml from FOS\RestBundle\Tests\Functional ``` We don't use cache in our tests but some of them are not in ``debug`` mode (will change soon) so the cache is automatically used. This PR fixes this deprecation by detecting if the cache used by the serializer is psr6 compliant or not (if it is, then it replaces the default metadata factory by an instance of the new class ``CacheClassMetadataFactory``, otherwise the second parameter of the ``ClassMetadataFactory`` is used). Commits ------- 15579d5 [FrameworkBundle] Deprecate framework.serializer.cache eccbffb [Serializer] Improve a deprecation message 96e418a Revert "[FrameworkBundle] Fallback to default cache system in production for serializer"

Uh oh!