EDIT: 'keep_as_list' also breaks embedded forms that contain unmapped file upload inputs. Model-, norm- and viewData return empty string/null instead of an UploadedFile object.

Hello. I also encountered unexpected behavior of the new option:
symfony/form/Extension/Core/EventListener/ResizeFormListener.php:159 removes $form and then re-adds it, but does not re-populate the data. So the data that was submitted inside the collection is lost when rendering the submitted form

Happened on the same just now with CollectionType with 'delete_empty' => true, 'keep_as_list' => true,.

If form submission is successful, then data on the entity is updated properly with a list.

However if submission fails and submitted data has an empty input you will end up with all empty inputs for the collection in the updated form.

Can anyone of create a small example application that allows to reproduce the behaviour you observe?

Can anyone of create a small example application that allows to reproduce the behaviour you observe?

Will have to think about that.

Right now it seems adding $form->setData($data); at the end of onSubmit() after $event->setData($data); in ResizeFormListener.php fixes it.

Can anyone of create a small example application that allows to reproduce the behaviour you observe?

https://github.com/whataboutpereira/symfony-form-keep-as-list-issue

Latest commit built on the symfony skeleton app.

If you enter anything in the three collection fields, the data is wiped in the refreshed form when keep_as_list in on.

The aforementioned adding $form->setData($data); at the end of onSubmit() after $event->setData($data); in ResizeFormListener.php fixes it.

Now that I look at it more closely, $form->setData($data) should be at the end of the $this->keepAsList block.

Or even set the data right when adding new children.

Unfortunately I'm not knowledgeable enough as to which is the best path. :)

                $form->add($index, $this->type, array_replace([
                    'property_path' => '[' . $index . ']',
+                    'data' => $child->getData(),
                ], $this->options));

Now I see both $form->setData($data) and 'data' => $child->getData() are wrong, because submitted data will be overwritten with initial data set with 'data' in options. This fares better:

            foreach ($formReindex as $index => $child) {
                $form->add($index, $this->type, array_replace([
                    'property_path' => '[' . $index . ']',
                ],
-                $this->options));
+                $this->options, ['data' => $child->getData()]));
            }

Description

When mapping a CollectionType ('allow_delete' => true) to an entity property of type ArrayCollection, the following exception is thrown when setting the new 'keep_as_list' option true:

array_values(): Argument #1 ($array) must be of type array, Doctrine\ORM\PersistentCollection given

I now saw this one as well when working with an ArrayCollection.

The tests in src\Symfony\Component\Form\Tests\Extension\Validator\Type\FormTypeValidatorExtensionTest.php seem to operate against an array of objects, it doesn't test authors as ArrayCollection so doesn't catch this issue.

So there seem to be at least two separate issues with keep_as_list:

1. keep_as_list gives an exception when the collection is an ArrayCollection.
2. Elements in a plain array lose their values when re-displaying the form with submitted data.

More info here

I've just encountered a related problem with the keep_as_list option of CollectionType.
When there are constraints on fields (in the form, not in the model) in the embedded form in a CollectionType, those constraints are simply ignored. They don't even bubble at the root of the form.

If I switch the keep_as_list to false, the constraints are working like before.

Seems to me this useful features is not fully functional. As someone mentioned above, I'm accustomed to reindex myself so a fix is not critical.

Sorry I wish I could provide a link to my project but sorry, it's currently private on github because it's a mess

PS : I don't use an ArrayCollection nor Doctrine, it's just a plain normal PHP array