Handle add to cart of simple configurable products

Introduce possibility to handle adding to cart of configurable products
on setups when swatches module is not enabled

Author: IvanChepurnyi

lib/generate/collector/checkout.js

@@ -39,18 +39,37 @@ const checkout = async (
 
     // Select option for every swatch if there are any.
     await page.evaluate(() => {
-        Array.from(
-            document.querySelectorAll(
-                '.product-options-wrapper .swatch-attribute'
-            )
-        ).forEach((swatch) => {
+        const swatches = document.querySelectorAll(
+            '.product-options-wrapper .swatch-attribute'
+        );
+        Array.from(swatches).forEach((swatch) => {
             const swatchOption = swatch.querySelector(
                 '.swatch-option:not([disabled])'
             );
             swatch.querySelector('.swatch-input').value =
                 swatchOption.getAttribute('option-id') ||
                 swatchOption.getAttribute('data-option-id');
         });
+
+        if (swatches.length) {
+            return;
+        }
+
+        Array.from(
+            document.querySelectorAll(
+                '.product-options-wrapper .super-attribute-select'
+            )
+        ).forEach((select) => {
+            select.value = Array.from(select.options).reduce(
+                (selectedValue, option) => {
+                    return (
+                        selectedValue ||
+                        (option.value ? option.value : selectedValue)
+                    );
+                },
+                null
+            );
+        });
     });
 
     await Promise.all([