[LiveComponent] (Dynamic Form) Default values disappear for dynamically added fields

[momocode-de]

I have a LiveComponent for a form. This form has dependent fields which have been implemented with the dynamic-forms bundle. I have a situation where I have select fields that are only added when certain other fields have been filled in. These select fields should have a preselected value. To do this, I set the value in the corresponding fields in the object for the initial form values. The problem is that these values disappear when the fields are added and therefore no value is preselected in the fields. There is already an issue for this in the dynamic-forms bundle. I have now debugged it and found out what the problem is. This is due to the $clearMissing parameter of the Symfony\Component\Form::submit function. This parameter is true by default. The function is called here without the 2nd parameter. If I set the 2nd parameter to false, the problem is solved. I could create a PR for it now, but unfortunately I can't assess whether this would have unwanted side effects. Can anyone say? Is it ok to set the $clearMissing parameter to false in the ComponentWithFormTrait on submit?

[smnandre]

Hi @momocode-de, thank you for this very detailed report 🙇

I'd say, let's open this PR and we will iterate on it and see what effects it could have :)

[Huluti]

For me it's an important problem in Symfony UX because for a simple use-case like this with SymfonyCasts/dynamic-forms, you can't select a default value for the dependant field. Here for the month selector I would like to have the current month selected (December) instead of the first option (January).

[smnandre]

@Huluti There is an open PR, if you can have a look and discuss alternatives