I had been trying to use rest api for getting Configurable Products (Child products) using the rest API - https:url//rest/V1/configurable-products/sku/children

But, I am getting this framework error - "Method's return type must be specified using @return annotation. See Magento\Catalog\Model\ResourceModel\Product\Collection\Interceptor::load()"

"trace": "#0 /var/www/html/vendor/magento/framework/Reflection/TypeProcessor.php(291): Magento\Framework\Reflection\TypeProcessor->getMethodReturnAnnotation(Object(Laminas\Code\Reflection\MethodReflection))\n#1 /var/www/html/vendor/magento/framework/Reflection/MethodsMap.php(180): Magento\Framework\Reflection\TypeProcessor->getGetterReturnType(Object(Laminas\Code\Reflection\MethodReflection))\n#2 /var/www/html/vendor/magento/framework/Reflection/MethodsMap.php(115): Magento\Framework\Reflection\MethodsMap->getMethodMapViaReflection('Magento\\Catalog...')\n#3 /var/www/html/vendor/magento/framework/Reflection/DataObjectProcessor.php(83): Magento\Framework\Reflection\MethodsMap->getMethodsMap('Magento\\Catalog...')\n#4 /var/www/html/vendor/magento/framework/Reflection/CustomAttributesProcessor.php(76): Magento\Framework\Reflection\DataObjectProcessor->buildOutputDataArray(Object(Magento\Catalog\Model\ResourceModel\Product\Collection\Interceptor), 'Magento\\Catalog...')\n#5 /var/www/html/vendor/magento/framework/Reflection/CustomAttributesProcessor.php(53): Magento\Framework\Reflection\CustomAttributesProcessor->convertCustomAttribute(Object(Magento\Framework\Api\AttributeValue), '\\Magento\\Catalo...')\n#6 /var/www/html/generated/code/Magento/Framework/Reflection/CustomAttributesProcessor/Proxy.php(95): Magento\Framework\Reflection\CustomAttributesProcessor->buildOutputDataArray(Object(Magento\Catalog\Model\Product\Interceptor), '\\Magento\\Catalo...')\n#7 /var/www/html/vendor/magento/framework/Reflection/DataObjectProcessor.php(107): Magento\Framework\Reflection\CustomAttributesProcessor\Proxy->buildOutputDataArray(Object(Magento\Catalog\Model\Product\Interceptor), '\\Magento\\Catalo...')\n#8 /var/www/html/vendor/magento/framework/Webapi/ServiceOutputProcessor.php(118): Magento\Framework\Reflection\DataObjectProcessor->buildOutputDataArray(Object(Magento\Catalog\Model\Product\Interceptor), '\\Magento\\Catalo...')\n#9 /var/www/html/vendor/magento/framework/Webapi/ServiceOutputProcessor.php(78): Magento\Framework\Webapi\ServiceOutputProcessor->convertValue(Array, '\\Magento\\Catalo...')\n#10 /var/www/html/vendor/magento/module-webapi/Controller/Rest/SynchronousRequestProcessor.php(97): Magento\Framework\Webapi\ServiceOutputProcessor->process(Array, 'Magento\\Configu...', 'getChildren')\n#11 /var/www/html/vendor/magento/module-webapi/Controller/Rest.php(188): Magento\Webapi\Controller\Rest\SynchronousRequestProcessor->process(Object(Magento\Framework\Webapi\Rest\Request\Proxy))\n#12 /var/www/html/vendor/magento/framework/Interception/Interceptor.php(58): Magento\Webapi\Controller\Rest->dispatch(Object(Magento\Framework\App\Request\Http))\n#13 /var/www/html/vendor/magento/framework/Interception/Interceptor.php(138): Magento\Webapi\Controller\Rest\Interceptor->___callParent('dispatch', Array)\n#14 /var/www/html/vendor/magento/framework/Interception/Interceptor.php(153): Magento\Webapi\Controller\Rest\Interceptor->Magento\Framework\Interception\{closure}(Object(Magento\Framework\App\Request\Http))\n#15 /var/www/html/generated/code/Magento/Webapi/Controller/Rest/Interceptor.php(23): Magento\Webapi\Controller\Rest\Interceptor->___callPlugins('dispatch', Array, Array)\n#16 /var/www/html/vendor/magento/framework/App/Http.php(116): Magento\Webapi\Controller\Rest\Interceptor->dispatch(Object(Magento\Framework\App\Request\Http))\n#17 /var/www/html/vendor/magento/framework/App/Bootstrap.php(264): Magento\Framework\App\Http->launch()\n#18 /var/www/html/pub/index.php(33): Magento\Framework\App\Bootstrap->run(Object(Magento\Framework\App\Http\Interceptor))\n#19 {main}" }

Upon Investigation, I found that - In vendor\magento\module-configurable-product\Model\LinkManagement.php has function "public function getChildren($sku)". When I change the following line (104) -
$this->dataObjectHelper->populateWithArray($productDataObject, $attributes, \Magento\Catalog\Api\Data\ProductInterface::class);

$this->dataObjectHelper->populateWithArray($productDataObject, [], \Magento\Catalog\Api\Data\ProductInterface::class);

[ { "sku": null, "status": 1, "product_links": [], "tier_prices": [] }, { "sku": null, "status": 1, "product_links": [], "tier_prices": [] }, { "sku": null, "status": 1, "product_links": [], "tier_prices": [] }, ... ]

I had been trying to use rest api for getting Configurable Products (Child products) using the rest API - https:url//rest/V1/configurable-products/sku/children

But, I am getting this framework error - "Method's return type must be specified using @return annotation. See Magento\Catalog\Model\ResourceModel\Product\Collection\Interceptor::load()"

"trace": "#0 /var/www/html/vendor/magento/framework/Reflection/TypeProcessor.php(291): Magento\Framework\Reflection\TypeProcessor->getMethodReturnAnnotation(Object(Laminas\Code\Reflection\MethodReflection))\n#1 /var/www/html/vendor/magento/framework/Reflection/MethodsMap.php(180): Magento\Framework\Reflection\TypeProcessor->getGetterReturnType(Object(Laminas\Code\Reflection\MethodReflection))\n#2 /var/www/html/vendor/magento/framework/Reflection/MethodsMap.php(115): Magento\Framework\Reflection\MethodsMap->getMethodMapViaReflection('Magento\\Catalog...')\n#3 /var/www/html/vendor/magento/framework/Reflection/DataObjectProcessor.php(83): Magento\Framework\Reflection\MethodsMap->getMethodsMap('Magento\\Catalog...')\n#4 /var/www/html/vendor/magento/framework/Reflection/CustomAttributesProcessor.php(76): Magento\Framework\Reflection\DataObjectProcessor->buildOutputDataArray(Object(Magento\Catalog\Model\ResourceModel\Product\Collection\Interceptor), 'Magento\\Catalog...')\n#5 /var/www/html/vendor/magento/framework/Reflection/CustomAttributesProcessor.php(53): Magento\Framework\Reflection\CustomAttributesProcessor->convertCustomAttribute(Object(Magento\Framework\Api\AttributeValue), '\\Magento\\Catalo...')\n#6 /var/www/html/generated/code/Magento/Framework/Reflection/CustomAttributesProcessor/Proxy.php(95): Magento\Framework\Reflection\CustomAttributesProcessor->buildOutputDataArray(Object(Magento\Catalog\Model\Product\Interceptor), '\\Magento\\Catalo...')\n#7 /var/www/html/vendor/magento/framework/Reflection/DataObjectProcessor.php(107): Magento\Framework\Reflection\CustomAttributesProcessor\Proxy->buildOutputDataArray(Object(Magento\Catalog\Model\Product\Interceptor), '\\Magento\\Catalo...')\n#8 /var/www/html/vendor/magento/framework/Webapi/ServiceOutputProcessor.php(118): Magento\Framework\Reflection\DataObjectProcessor->buildOutputDataArray(Object(Magento\Catalog\Model\Product\Interceptor), '\\Magento\\Catalo...')\n#9 /var/www/html/vendor/magento/framework/Webapi/ServiceOutputProcessor.php(78): Magento\Framework\Webapi\ServiceOutputProcessor->convertValue(Array, '\\Magento\\Catalo...')\n#10 /var/www/html/vendor/magento/module-webapi/Controller/Rest/SynchronousRequestProcessor.php(97): Magento\Framework\Webapi\ServiceOutputProcessor->process(Array, 'Magento\\Configu...', 'getChildren')\n#11 /var/www/html/vendor/magento/module-webapi/Controller/Rest.php(188): Magento\Webapi\Controller\Rest\SynchronousRequestProcessor->process(Object(Magento\Framework\Webapi\Rest\Request\Proxy))\n#12 /var/www/html/vendor/magento/framework/Interception/Interceptor.php(58): Magento\Webapi\Controller\Rest->dispatch(Object(Magento\Framework\App\Request\Http))\n#13 /var/www/html/vendor/magento/framework/Interception/Interceptor.php(138): Magento\Webapi\Controller\Rest\Interceptor->___callParent('dispatch', Array)\n#14 /var/www/html/vendor/magento/framework/Interception/Interceptor.php(153): Magento\Webapi\Controller\Rest\Interceptor->Magento\Framework\Interception\{closure}(Object(Magento\Framework\App\Request\Http))\n#15 /var/www/html/generated/code/Magento/Webapi/Controller/Rest/Interceptor.php(23): Magento\Webapi\Controller\Rest\Interceptor->___callPlugins('dispatch', Array, Array)\n#16 /var/www/html/vendor/magento/framework/App/Http.php(116): Magento\Webapi\Controller\Rest\Interceptor->dispatch(Object(Magento\Framework\App\Request\Http))\n#17 /var/www/html/vendor/magento/framework/App/Bootstrap.php(264): Magento\Framework\App\Http->launch()\n#18 /var/www/html/pub/index.php(33): Magento\Framework\App\Bootstrap->run(Object(Magento\Framework\App\Http\Interceptor))\n#19 {main}" }

Upon Investigation, I found that - In vendor\magento\module-configurable-product\Model\LinkManagement.php has the function "public function getChildren($sku)". When I change the following line (104) -
$this->dataObjectHelper->populateWithArray($productDataObject, $attributes, \Magento\Catalog\Api\Data\ProductInterface::class);

$this->dataObjectHelper->populateWithArray($productDataObject,
[], \Magento\Catalog\Api\Data\ProductInterface::class);

[
    {
        "sku": null,
        "status": 1,
        "product_links": [],
        "tier_prices": []
    },
    {
        "sku": null,
        "status": 1,
        "product_links": [],
        "tier_prices": []
    },
    {
        "sku": null,
        "status": 1,
        "product_links": [],
        "tier_prices": []
    },
    ...
]