[Form] Example of customizing EnumType labels

[robinbrisa]

Default behavior when creating a EnumType form element is that the choice labels displayed to the user are the enum names.

This PR adds an example of how to use a function inside an enum to return labels and how to bind this function to the form element.

[xabbuh]

Adding this method to the enum class starts mixing data and presentation which I would not advise. Let's configure the choice label using a closure instead (see comment below).

[xabbuh]

Suggested change

	return $choice->label();
	return match ($choice) {
	TextAlign::Left => 'text_align.left.label',
	TextAlign::Center => 'text_align.center.label',
	TextAlign::Right => 'text_align.right.label',
	};

[robinbrisa]

This would work if you only needed to display the labels in your form, but if you also need them to appear anywhere else in your application I think adding a method in the enum class is a better solution. I don't think adding presentation methods in enum classes is a bad practice.

[xabbuh]

If I had different places where I needed the label, I would go with a separate class that maps enum instances to labels to be honest.

[robinbrisa]

That might be a way to do it but maybe a bit overkill. Even the PHP documentation suggests adding a label method in enum classes in their examples : https://www.php.net/manual/fr/language.enumerations.examples.php

[javiereguiluz]

I don't know what to say here. I think both of you gave good reasons to do opposite things.

Let's ask @wouterj and @OskarStark. Thanks!

[wouterj]

I agree with @xabbuh here. I understand your point, @robinbrisa, and it is also proven by the official PHP docs.

However, I would say that an enum can ship a generic presentation layer. The labels provided in this example indirectly couple the Enum's presentation layer to the Symfony Translation component - without it, the labels render worse human readable than their default string representation from the BackedEnum.
In that case, I would favor to keep the enum decoupled from Symfony Translation and handle the presentation in the layer that is responsible for mapping between Symfony Translation and the Enum, which is this function :)

[HeahDude]

Another way to see it would be to have MyEnum::getLabel() and/or MyEnum::getTranslationKey() to make it more reusable with respect for different layers.
However for the docs I agree this callable is a good way to go.

[wouterj]

Suggested change

	])
	]);

[javiereguiluz]

Robin, thanks and congrats on your first Symfony Docs contribution 🎉

@xabbuh @wouterj @HeahDude thanks for the review. I did the requested changes while merging (see c4de976)