Problem/Motivation
Drupal 9 will release with either Symfony 4 or Symfony 5.
In order to be able to do that, we should make Drupal 8 as compatible with Symfony 4 as possible:
1. Remove all use of deprecated Symfony 3 and Symfony 4 APIs.
2. Eventually allow Drupal 8 to be installed with Symfony 4 via composer, although packaging would stick to Symfony 3.
Proposed resolution
This issue is mostly a testing issue, patches to be committed should be split out and posted as child issues of #2937984: [META] Symfony 4.0 compatibility
Remaining tasks
User interface changes
API changes
Data model changes
Release notes snippet
Original report by @martin107
I want to pull and few threads together into an action.
The correctness of this has really bugged me in the few months since I read it....... in a good way.
https://www.drupal.org/project/drupal/issues/2937984#comment-12570221
Have an issue with a patch that updates to Symfony 4 so we can see if it passes or not.
And more publicly there have been blog post about the same idea
https://www.thirdandgrove.com/long-road-drupal-9
https://dri.es/when-should-we-release-drupal-9
The posts I summaries as
"Given the hard 2021 deadline and the desire to give contrib a year to adjust we better pick up our collective skirts and get a move on."
Please also note that a second correct perspective is to say
We have identified technical debut and parcelled it up into the form of entries in the DeprecationListenerTrait and are slowly clearing things up.
But my response is still to think ...
That is a nice, but with such a large code base there will be some green bug eyed monsters just in the cracks
We can act now with such a simple simple pipe cleaning exercise exercise.
So my first idiot style move is to change all symfony-X version numbers to "*" as see what breaks
