Upgraded Symfony 4.4 to 5.4

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I’ve upgraded my website to Symfony 5.4 from 4.4. I’ve continued on without Symfony Flex, as I had when updating from 3.4 to 4.4. The procedure was fairly similar to that, fixing any Symfony 4 deprecations and then updating the composer version constraints, fixing anything broken after that. I also switched from requiring the symfony/symfony repo to requiring individual components. It went fairly smoothly, aside from needing to fix a few things after the composer update.

Symfony components

I switched from depending on symfony/symfony to depending on the individual components I need. Symfony recommends this now and it can save significantly on composer install / update times. As such, it can help with the upgrade process in general. The only weird thing with this was that, since I was no longer specifying some sub-dependencies, they were going up to 5.x before I had upgraded to it, showing some irrelevant deprecation warnings.

To determine what dependencies to put in place of the mono-repo, I looked at the 4.4 composer.json file, particularly at these sections:

  • require
  • require-dev
  • autoload-dev

The composer changes I needed can roughly be seen in this commit. In require, the main ones I needed to add were:

  • "symfony/framework-bundle": "^4.4"
  • "symfony/console": "^4.4"
  • "symfony/security-bundle": "^4.4"
  • "symfony/twig-bundle": "^4.4"

I also needed to add a conflict section like:

"conflict": {
    "symfony/symfony": "*"
}

to force it to replace symfony/symfony in the vendor folder.

If using symfony/var-dumper, the autoload-dev file path for it must be changed to "vendor/symfony/var-dumper/Resources/functions/dump.php".

I had to add some others over time, but those were the main ones my simple site needed immediately.

Onwards and upwards

Moving to 5.4 was roughly as simple as in Symfony’s upgrade docs (excluding section 3, which is flex related), basically fixing deprecations and then changing the versions in composer.json. I did have to fix a few issues afterward though. The deprecations will show in Symfony’s web profiler using symfony/web-profiler-bundle and in PHPUnit tests with symfony/phpunit-bridge. They may also show in the PHP or Apache error log if settings allow it.

As I said above, since switching to independent Symfony components, some of the dependencies that were not specified directly ended up going to 5.x versions before I switched my project. This resulted in some deprecations that were within Symfony / third-party code that I could do nothing about. So I fixed all the deprecations in my own code, and when I did the upgrade, the others were fixed by the upgraded third-party versions.

Some of the deprecations I had to fix were:

  • Symfony\Component\Debug\Exception\FlattenException was switched to Symfony\Component\ErrorHandler\Exception\FlattenException, changed in my use statements
  • Symfony\Component\HttpKernel\Event\FilterResponseEvent was switched to Symfony\Component\HttpKernel\Event\ResponseEvent, used as the typehint for an onKernelResponse() event I had
  • kernel.root_dir was removed, so I used a PHP constant in my bootstrap file and then set the parameter kernel.root_dir: !php/const TJM\SyWeb\APP_DIR in my config.yml so I wouldn’t have to change it elsewhere
  • in my dev routing, where I had a route to make viewing errors easier, I changed resource: "@TwigBundle/Resources/config/routing/errors.xml" to resource: "@FrameworkBundle/Resources/config/routing/errors.xml"
  • added return 0; to execute() methods of commands
  • new Process() became Process::fromShellCommandline()
  • custom error controller config was moved from twig to framework config, eg: 
    framework:
+  error_controller: 'PublicApp\Controller\MetaController::exceptionAction'
twig:
-  exception_controller: 'PublicApp\Controller\MetaController::exceptionAction'
+  exception_controller: null
  • some methods required specifying return types

To do the actual upgrade, in composer.json, I changed all of the "^4" or "^4.4" for the symfony namespaced packages to "^5.4", changed the twig/twig version to "2.13|^3.0.4", and then did composer update. It worked fine for me.

I’m glad that the upgrade went so smoothly and I have the newer features and longer maintained dependencies. It might be more work to upgrade a more complex application than my simple website. Most third-party packages are not as good about giving deprecations for everything and following semver as the Symfony project. But it should be doable just working through each issue, one at a time.