[LiveComponent] Fix ComponentWithFormTrait::extractFormValues() with edge cases

[smnandre]

Q	A
Bug fix?	yes
New feature?	no
Issues	Fix #2487
License	MIT

#2403 fixed an old bug to simulate browser behaviour when a select field has no option selected, no placeholder, and is required (it then uses the first option)
#2425 and #2426 fixed the way we handled empty strings as placeholders

In #2487 @maciazek explained us how a custom type with a "choices" option became unusable since the last changes.

Also.. while I was reading all this I realized we returned wrong values here when "option groups" were used.. leading to other problems.

I updated the code of extractFormValues() method to:

• check if most of the caracteristic keys added in ChoiceType::buildView were defined in the $view->vars, to ensure we are dealing with a <select> field built by a ChoiceType
• fetch recursively the value of the first displayed option (even with groups)

[maciazek]

I can confirm that this patch resolved my specific case with custom form type and "choices" option. Thank you.

[norkunas]

Something is more going on here.
I was getting An exception has been thrown during the rendering of a template ("Warning: Undefined array key "expanded""). and so I've tried this patch, then started to get:
An exception has been thrown during the rendering of a template ("Warning: Undefined array key """).

While #2490 works for me

[maciazek]

Something is more going on here. I was getting An exception has been thrown during the rendering of a template ("Warning: Undefined array key "expanded""). and so I've tried this patch, then started to get: An exception has been thrown during the rendering of a template ("Warning: Undefined array key """).

While #2490 works for me

I think it could happen when form has some ChoiceType field, which has 'choices' set as empty array. In that case
https://github.com/smnandre/ux/blob/cd353fc7a0689b9cee5da252f977acb420176d96/src/LiveComponent/src/ComponentWithFormTrait.php#L269
returns true, and then the error itself comes from:
https://github.com/smnandre/ux/blob/cd353fc7a0689b9cee5da252f977acb420176d96/src/LiveComponent/src/ComponentWithFormTrait.php#L284

Seems that some additional check is needed (if 'choices' is array and if it is not empty?)

[smnandre]

Entirely my fault here.

As you can see here i checked for the "choices" existence.
https://github.com/smnandre/ux/blob/cd353fc7a0689b9cee5da252f977acb420176d96/src/LiveComponent/src/ComponentWithFormTrait.php#L275C33-L275C34

I decided later on to "optimize" and moved the check first, adding an isset in the operation when the key was not defined.... and losing then my original goal: ensure there is one value.

[smnandre]

This should work better now. Thank you very much to both of you.