[LiveCollection] LiveCollectionType may reuse removed Doctrine entity when adding a new item due to index reuse

[JacquesMougin]

Description

I'm encountering an issue when using LiveComponent + LiveCollectionType with a Doctrine Collection.

The problem seems related to how $formValues indexes are handled when removing and adding items.

Context

Symfony UX LiveComponent version: 2.31
Symfony version: 7.4.1
Doctrine/ORM version: 3.5.7
PHP version: 8.4

I'm using:

• Symfony UX LiveComponent
• LiveCollectionType
• A Doctrine collection inside a form.

Current behaviour

Suppose the collection initially contains 3 elements.

Indexes in $formValues are:

0, 1, 2

If I remove the last element using the remove action from LiveCollectionTrait, index 2 is removed and the array keys become:

0, 1

Then, when adding a new element via the add action, the following code is executed in LiveCollectionTrait -> addCollectionItem (line 36) :

$index = [] !== $data ? max(array_keys($data)) + 1 : 0;

In this case:

max index = 1
new index = 2

So the new item is inserted at index 2.

The issue

Because index 2 previously existed and was mapped to a Doctrine entity, the newly added entry ends up being mapped back to the previously removed entity instead of creating a new one.

This leads to unexpected behavior where:

• the removed entity appears again
• a new object is not actually created

Expected behaviour

When adding a new element after a removal, a new entry should always be created, without reusing a previously removed reference.

Possible cause

The issue seems to be that the index used in $formValues is derived from the current max key, which may correspond to a previously removed entry.

This becomes problematic when working with Doctrine collections and form data mapping.

Possible solution ideas

The workaround I've found is :

#[LiveProp]
public int $maxInitialKey = 0;

#[PostMount]
public function postMount(): void
{
    $this->maxInitialKey = max($this->entity->collection->getKeys());
}

#[LiveAction]
public function addCollectionItem(PropertyAccessorInterface $propertyAccessor, #[LiveArg] string $name): void
{
    $key = $this->maxInitialKey + 1;
    if (array_key_exists($key, $this->formValues['collection'])) {
        $key = max(array_keys($this->formValues['collection'])) + 1;
    }

    $this->formValues['collection'][$key] = [];
}

Question

Is this the expected behavior of LiveCollectionType, or could this be considered a bug when working with Doctrine collections?