[Laravel] Unexpected non-iterable value for to-many relation due to snake_case attribute name

[cay89]

API Platform version(s) affected: 4.1.18

Description
After upgrading from version 4.1.3 to 4.1.18, a Unexpected non-iterable value for to-many relation. error occurs when calling a GetCollection endpoint.

Here is the relevant model:

#[
    ApiResource(
        uriTemplate: '/list/types',
        operations: [
            new GetCollection(
                name: 'list-types',
                parameters: [
                    new QueryParameter(
                        key: 'filter[id]',
                        filter: EqualsFilter::class,
                        property: 'id',
                    ),
                    new QueryParameter(
                        key: 'filter[key]',
                        filter: EqualsFilter::class,
                        property: 'key',
                    ),
                    new QueryParameter(
                        key: 'filter[status]',
                        filter: EqualsFilter::class,
                        property: 'status',
                    ),
                    new QueryParameter(key: 'sort', filter: SortFilter::class),
                ],
            ),
        ],
    ),
]
class ListType extends AbstractModel
{
    protected $fillable = ['key', 'status'];

    protected function casts(): array
    {
        return [
            'key' => ListTypeKey::class,
            'status' => ListTypeStatus::class,
        ];
    }

    /**
     * @return HasMany<ListItem, $this>
     */
    public function listItems(): HasMany
    {
        return $this->hasMany(ListItem::class, 'type_key', 'key');
    }
}

The exception is thrown in \ApiPlatform\Serializer\AbstractItemNormalizer::getAttributeValue():

$attributeValue = $this->propertyAccessor->getValue($object, $attribute);

if (!is_iterable($attributeValue)) {
    throw new UnexpectedValueException('Unexpected non-iterable value for to-many relation.');
}

In this case, $attribute is list_items, but the actual relation on the model is listItems, so $attributeValue ends up being null, triggering the exception.

This issue did not occur in version 4.1.3 — it started happening after upgrading to 4.1.18, so something must have changed in the serialization or name conversion logic since then.

[stale]

This issue has been automatically marked as stale because it has not had recent activity. It will be closed if no further activity occurs. Thank you for your contributions.

[PicassoHouessou]

I am having the same with BelongsToMany

#[ApiProperty(serialize: new Groups(['product_association:read', 'product_association:write']), property: 'associatedProducts')]

public function associatedProducts(): BelongsToMany
{
    return $this->belongsToMany(Product::class,'product_association_products','association_id','owner_id');
}