[DependencyInjection] Clarify the #[Target] attribute

[HypeMC]

The #[Target] attribute seems to be a constant source of confusion for developers, as evident by:

• Cannot autowire service (...) when using #[Target] attribute in Symfony 6.3 symfony#50541
• [DependencyInjection] Target parameter attribute does not work for Services symfony#51565
• [DependencyInjection] Attribute #[Target()] does not work symfony#54578

Also, the example given is either unclear or just wrong. Hopefully, this helps clarify things.

[javaDeveloperKid]

Good clarification. I've never understood how this attribute works 😄 I had two interpretations but both wrong.

Btw. I think this should also be clarified in the source code above $name constructor parameter doc block and class doc block (the latter is a little better but still can be improved). https://github.com/symfony/symfony/blob/7.1/src/Symfony/Component/DependencyInjection/Attribute/Target.php

[OskarStark]

@nicolas-grekas a final review from your side would be helpful, thanks

[nicolas-grekas]

LGTM but maybe we should tell about the debug:autowiring command, which does report the target name since symfony/symfony#50718?

[HypeMC]

@nicolas-grekas Good idea, I've created a followup PR since this one targets 5.4, and the feature was introduced in 6.4.

[javiereguiluz]

@HypeMC thanks for this contribution and sorry it took us so long to merge it.

[javiereguiluz]

@HypeMC I upmerged this in 6.4, 7.0, 7.1 and 7.2 branches.

I'm not sure I did everything right, because in 6.4 we show both upperTransformer and shoutyTransformer. I don't know if both are correct or the "shouty" thing is a leftover from 5.4 branch and 6.4 branch was wrong before merging this PR.

If you can, please review it. See ad1e3b2

[HypeMC]

@javiereguiluz Yep, everything looks ok, I see you've also merged the follow up PR.