Exception #0 (Exception): Warning: Array to string conversion in /var/www/html/vendor/magento/module-swatches/Helper/Data.php on line 200

[lumnn]

Preconditions

Magento Version : Magento 2.4.7-p4

ElasticSuite Version : 2.11.13

Environment : both

Third party modules :

Steps to reproduce

1. Add color swatch and enable filtering
2. Have some products with custom images for swatches, and some without swatch variant image
3. Filter by few colours

Expected result

1. Filtering works

Actual result

Exception #0 (Exception): Warning: Array to string conversion in /var/www/html/vendor/magento/module-swatches/Helper/Data.php on line 200
<pre>#1 array_diff_assoc() called at [vendor/magento/module-swatches/Helper/Data.php:200]
#2 Magento\Swatches\Helper\Data->loadFirstVariation() called at [vendor/magento/module-swatches/Helper/Data.php:232]
#3 Magento\Swatches\Helper\Data->loadFirstVariationWithImage() called at [vendor/smile/elasticsuite/src/module-elasticsuite-swatches/Model/Plugin/ProductImage.php:101]
#4 Smile\ElasticsuiteSwatches\Model\Plugin\ProductImage->loadSimpleVariation() called at [vendor/smile/elasticsuite/src/module-elasticsuite-swatches/Model/Plugin/ProductImage.php:47]
#5 Smile\ElasticsuiteSwatches\Model\Plugin\ProductImage->beforeGetImage() called at [vendor/magento/framework/Interception/Interceptor.php:121]
#6 Magento\Catalog\Block\Product\ListProduct\Interceptor->Magento\Framework\Interception\{closure}() called at [vendor/magento/framework/Interception/Interceptor.php:153]
#7 Magento\Catalog\Block\Product\ListProduct\Interceptor->___callPlugins() called at [generated/code/Magento/Catalog/Block/Product/ListProduct/Interceptor.php:329]

I've looked into where array comes to in first place and I've found that in src/vendor/smile/elasticsuite/src/module-elasticsuite-swatches/Model/Plugin/ProductImage.php:79 there is condition that adds option ids to array, which becomes a bit of a mixture of labels and ids.

Below screenshot of 2 debugging dump lines added after line 80

$filterArray[$code][] = $this->swatchHelperData->getOptionIds($attribute, $value);
dump($filterArray);
dump($this->swatchHelperData->getOptionIds($attribute, $value));

[vahonc]

We have several issues with this problem, that's why I tried to investigate it more deeply and want to share my thoughts.

The original Magento\Swatches\Model\Plugin\ProductImage plugin determines the correct simple product image for configurable products on category pages, based on the current layered navigation filters (e.g., color swatches).

The Smile_ElasticsuiteSwatches historically extended this plugin and modified its getFilterArray() method to include both swatch labels and option IDs when constructing the $filterArray parameter used to load simple variations.

Example of the previous (problematic) behavior:

$filterArray = [
    'colour' => [
        'Classic Navy',
        'Red',
        'Sandstone Mottle',
        [12582, 10896, 12616]
    ]
];

This was originally implemented to improve compatibility with older Magento versions, where request parameters contained swatch labels rather than numeric option IDs.

Problem:
In modern Magento 2.4+ releases, filter parameters already contain numeric option IDs. Therefore extended logic of our plugin introduces mixed data types (strings + arrays of ints) into $filterArray.

When passed into Magento\Swatches\Helper\Data::loadFirstVariationWithImage(), this inconsistent structure eventually reaches loadFirstVariation(), where the following core logic is executed:

$attributesData = array_diff_assoc($superAttributes, $attributes);

Because $superAttributes contains nested arrays instead of scalar values, PHP triggers a warning: Array to string conversion in module-swatches/Helper/Data.php:200 and breaks the product image resolution process in some cases.

Fix:
The solution is to replace (or merge), rather than append, the result of getOptionIds(...) into $filterArray. This ensures that $filterArray always contains flat arrays of scalar values (option IDs only):

$filterArray = [
   'colour' => [12582, 10896, 12616]
];

This fully restores compatibility with Magento's native swatch helper methods and eliminates the "Array to string conversion" warning.

Summary:
We have two clean paths forward:

Option 1:
Remove the deprecated plugin, cause:

• Magento core handles swatch image resolution well in 2.4.6+.
• So it looks like ElasticSuite no longer needs this custom logic.
• This is the safest long-term move.

Option 2:
Keep the plugin, but patch getFilterArray(). If we still need ElasticSuite’s behavior for layered filters + swatch image loading or backward compatibility with legacy ElasticSuite versions.

@rbayet, what do you think about that?

BR,
Vadym

[rbayet]

Hello @vahonc,

I'll have to digest this one on a day with dual monitors available, to compare both plugins both pre and post 2.4.x.

Regards,

[cptX]

Guys just installed 2.4.8-p3 and my site crashed, cannot access the admin panel because of this issue!! It's a production site, what can I do as a fast solution??? Spent 8 hours already and finally arrived here which I hope is the source of the problem!

[cptX]

I solved the problem temporarily by replacing the loadSimpleVariation function in vendor/smile/elasticsuite/src/module-elasticsuite-swatches/Model/Plugin/ProductImage.php with this

private function loadSimpleVariation(Product $parentProduct, array $filterArray)
{
    $childProduct = null;

    try {
        // Try to load a child variation using the provided filters
        $childProduct = $this->swatchHelperData->loadVariationByFallback($parentProduct, $filterArray);

        // If a variation is found but has no valid image, try to find one that does
        if ($childProduct && (!$childProduct->getImage() || $childProduct->getImage() === 'no_selection')) {
            $childProductWithImage = $this->swatchHelperData->loadFirstVariationWithImage($parentProduct, $filterArray);
            if ($childProductWithImage && $childProductWithImage->getImage() && $childProductWithImage->getImage() !== 'no_selection') {
                $childProduct = $childProductWithImage;
            }
        }
    } catch (\Throwable $e) {
        // Log any unexpected issue (e.g., malformed array, type errors)

    }

    // Fallback to parent product if no valid child was found
    if (!$childProduct instanceof Product) {
        $childProduct = $parentProduct;
    }

    return $childProduct;
}

Please suggest or prepare a more permanent solution!

For reference I give here the link for a similar issue that may has the same root cause #2619