I don't understand it completely, but it seems like you're using an EntityType while you should be using a collection type of sorts?

I added two tests here #23930

AFAIK the initial & expected data for EntityType with multiple = true should be an ArrayCollection instance.

Even though, an array is allowed, it shouldn't be recommended right now, because the core MergeCollectionListener doesn't care about the data type of the normalized data:

Hence $event->getForm()->getNormData() and $event->getData() won't have the same data type and the ArrayCollection type is loses if non "empty" data is provided by default.

Later, you'll needs take care about ambiguous data type resultant.

However, I think passing an array should be allowed too and the data type resultant should be consistent with the default data type. I can provide a solution for it, if it is what we want.

This is where that's not true - when an empty array is provided as default data:

then the result will be an empty ArrayCollection() instead of array().

Status: Confirmed

The solution to be consistent with default data type provided:

- if (!$dataToMergeInto) {
+ if (null === $dataToMergeInto) {

and the resulting data type should be consistent:

• If an array was given => an array is retrieved.
• If an ArrayCollection was given => an ArrayCollection is retrieved.

@stoccc could you try it?

@yceruto OK, it works. If I give an array, I always get an array; if I give an ArrayCollection, I always get an ArrayCollection

@stoccc If you prefer, you can provide the fix and update your PR, or let me know to submit a new one :)

@yceruto ok, I committed your changes

@yceruto I created new PR #23980 against 2.7. It seems that in php 5.3 tests pass, while in php 7 and 7.1 they don't pass. I can't figure out why. In my installation with 2.8 on php 7.0.10 I don't have problems. :(

I have same problem with Symfony 3.3.6 (PHP 5.6)