Symfony version(s) affected: symfony/framework-bundle 4.1.8+

Description
I'm working on a command that use metadata for adding style to workflow dumps.

The configuration is:

framework:
    workflows:
        pull_request:
            # …
            transitions:
                submit:
                    from: start
                    to: travis
                    metadata:
                        title: transition submit title
                        style:
                            label: 'My custom label'
                            arrow_color: '#0088FF'
                            label_color: 'Red'
                # …

And I get metadata with $this->workflowMetadata->getMetadata('style', $transition): https://github.com/alexislefebvre/SymfonyWorkflowStyleBundle/blob/ce5d5923cedd2a3b41e51386faf56a9888880739/src/Symfony/Component/Workflow/Dumper/PlantUmlDumper.php#L191

It worked one week ago but it is broken today: no data is returned.

I identified that it comes from symfony/framework-bundle, it breaks if I install v4.1.8 or v4.2.0.

How to reproduce
Clone https://github.com/alexislefebvre/SymfonyWorkflowStyleBundle, install dependencies and run tests:

git clone git@github.com:alexislefebvre/SymfonyWorkflowStyleBundle.git
cd SymfonyWorkflowStyleBundle/
composer install -vvv --profile --no-progress
php ./vendor/bin/phpunit

Tests pass.

Now remove conflict from composer.json, update dependencies and run tests again: Tests will fail because data in metadata is not available, so the PUML lacks the expected style.

Possible Solution

The problem is probably in one of these commits: symfony/framework-bundle@v4.1.7...v4.1.8

Only 2 commits were related to Workflow: symfony/framework-bundle@0647c5a (PR) and symfony/framework-bundle@1c1f86b (PR)

Additional context

We can see logs on Travis CI:

• job from 7 days ago: https://travis-ci.org/alexislefebvre/SymfonyWorkflowStyleBundle/jobs/459487618 →test passed
• job from today: https://travis-ci.org/alexislefebvre/SymfonyWorkflowStyleBundle/jobs/462429106 →test failed

The base code of my bundle has not been changed between these 2 jobs (¹), the only difference is that Symfony 4.1.8 and 4.2 have been released and these versions were installed today.

(¹) I only changed the configuration of failing jobs on Travis CI