[Resource] Fix ObjectToIdentifierTransformer bad implementation

[Zales0123]

Q	A
Bug fix?	yes
New feature?	no
BC breaks?	no
Deprecations?	no
Fixed tickets	#2979
License	MIT
Doc PR

While fixing #2979 I realized, that ObjectToIdentifierTransformer has inversely implemented methods! It caused mentioned bug, but also some others. There is open PR for this issue (#3085) with implemented custom transformer, but I think it will be not necessary after accepting this one ;)

[michalmarcinkowski]

@Zales0123 what about Behat scenario for this bug?

[Zales0123]

@michalmarcinkowski I can of course write scenario like this:

Scenario: Returning to shipping method page
    Given I go to the checkout start page
      And I fill in the shipping address to United States
      And I press "Continue"
     When I select the "FedEx" radio button
      And I press "Continue"
      And I click "Back"
     Then I should see "FedEx"

but it looks quite artificial. Do we need this only because some bug with some class has occurred? I'm really asking, not judging, sincerely :)

[michalmarcinkowski]

Could we remove this https://github.com/Sylius/Sylius/blob/master/src/Sylius/Bundle/SettingsBundle/Transformer/ObjectToIdentifierTransformer.php transformer then?

[michalmarcinkowski]

@Zales0123 answering to your question. I think we need a debate about the economy of tests and what we should test using Behat. The test suites are really big right now and I'm not sure what to do with them. On one hand we need tests for such basic, but crucial operations like moving back and forth on the checkout on the other hand we can't test every possible UI interaction with Behat, because it will lead to tests execution for days instead of minutes/hours 😄

[Zales0123]

It's more than satisfying answer 👍 Ok, so for now, I'll add this scenario, to be 100% sure that this nasty bug will not happen anymore.
If it's about deleting ObjectToIdentifierTransformer from SettingsBundle, I'm not certain. Yes, it provides identical logic as this fixed transformer from ResourceBundle, but it is not used as form transformer (notice, it's not even in Form-around namespace), implements specific ParameterTransformerInterface, which is used by SettingsBuilder and is generally totally different type of object.

[pjedrzejewski]

Thank you Mateusz! 👍