仅当选择了除一个属性之外的所有属性时，才能检查产品变型的可用性，而不能在此之前检查。
所有必要的数据都显示在产品页面上，因此您可以使用jQuery脚本来处理它。
在变体表单中，data-product_variations属性包含一个数组，其中包含产品变体的所有详细信息（变体ID、库存状态、所使用的属性等）。
然后，您可以在所选属性和可能的产品变化之间进行比较。
这个想法是这样的：
1.检查产品页面上是否有多个属性（下拉列表）
1.如果已选择除一个属性之外的所有属性（下拉列表），则获取选定选项的属性slug和属性值
1.它将它们与每个单一变体使用的属性进行比较，如果所选属性相同，则获取要选择的最后一个属性的库存状态
1.将文本 “Out of stock” 添加到产品变体没有库存的每个选项中。为此，它将使用woocommerce_update_variation_values事件，该事件在通过 AJAX 更新选项后触发（否则更改将被覆盖）
以下代码将适用于变量产品页面中的2个或更多属性（下拉列表）。

// add the text "Out of stock" to each option of the last unselected attribute dropdown
add_action( 'wp_footer', 'add_out_of_stock_text_to_the_last_unselected_attribute_dropdown' );
function add_out_of_stock_text_to_the_last_unselected_attribute_dropdown() {

    ?>
    <script type="text/javascript">

    // initializes a global variable that will contain the attribute values to be updated ("Out of stock")
    let globalAttributesToUpdate;

    jQuery(function($){

        // check if only one attribute is missing to be selected
        function isLastAttribute(){
            // if there is only one dropdown it returns false
            if ( $('form.variations_form select').length == 1 ) {
                return false;
            }
            // counts all selected attributes (excluding "Choose an option")
            let count = 0;
            $('form.variations_form select').each(function(){
                if ( $(this).find(':selected').val() ) {
                    count++;
                }
            });
            // if an attribute has not yet been selected, it returns true
            if ( $('form.variations_form select').length - count == 1 ) {
                return true;
            } else {
                return false;
            }
        }

        $('form.variations_form select').change(function() {
            if ( isLastAttribute() ) {
                // clear the global variable every time
                globalAttributesToUpdate = [];
                let attrToFind = {}; // contains an object with slug and value of the selected attributes
                let attrToSet; // contains the slug of the attribute not yet selected
                $('form.variations_form select').each(function(index,object){
                    if ( $(this).find(":selected").val() ) {
                        attrToFind[$(this).data('attribute_name')] = $(this).find(":selected").val();
                    } else {
                        attrToSet = $(this).data('attribute_name');
                    }
                });
                // gets the value of the "data-product_variations" attribute of the variations form
                let variationData = $('form.variations_form').data("product_variations");
                $(variationData).each(function(index,object) {
                    let attrVariation = object.attributes;
                    let attrVariationLenght = Object.keys(attrVariation).length;
                    let found = 0;
                    let toSet;
                    let valueToSet;
                    // check all possible combinations of attributes (for single variation)
                    // based on the selected attributes
                    $.each( attrVariation, function( attr, value ) {
                        if ( attr in attrToFind && attrToFind[attr] == value ) {
                            found++;
                        } else {
                            // if the variation is out of stock it gets slug and value to add the text "Out of stock"
                            if ( object.is_in_stock == false ) {
                                toSet = attr;
                                valueToSet = value;
                            }
                        }
                    });
                    // if only one attribute is missing
                    if ( attrVariationLenght - found == 1 ) {
                        if ( toSet == attrToSet ) {
                            let obj = {};
                            obj[toSet] = valueToSet;
                            globalAttributesToUpdate.push(obj);
                        }
                    }
                });
            }
        });

        // inserts the text "Out of stock" after updating the variations
        // based on the "globalAttributesToUpdate" global variable
        $('body').on('woocommerce_update_variation_values', function(){
            if ( globalAttributesToUpdate !== undefined && globalAttributesToUpdate.length ) {
                $.each( globalAttributesToUpdate, function( key, attribute ) {
                    $.each( attribute, function( attrName, attrValue ) {
                        $('select[name='+attrName+'] > option[value="'+attrValue+'"]').append( " (Out of stock)" );
                    });
                });
            }
        });
    });
    </script>
    <?php

}

• 该代码已经过测试，可以正常工作。请将其添加到活动主题的functions.php.*
  结果

相关答案

• How to add variation stock status to Woocommerce product variation dropdown
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add_filter('woocommerce_variation_option_name', 'display_price_in_variation_option_name');
function display_price_in_variation_option_name($term)
{
    global $wpdb, $product;
    $result = $wpdb->get_col("SELECT slug FROM {$wpdb->prefix}terms WHERE name = '$term'");
    $term_slug = (!empty($result)) ? $result[0] : $term;
    $query = "SELECT postmeta.post_id AS product_id
                FROM {$wpdb->prefix}postmeta AS postmeta
                    LEFT JOIN {$wpdb->prefix}posts AS products ON ( products.ID = postmeta.post_id )
                WHERE postmeta.meta_key LIKE 'attribute_%'
                    AND postmeta.meta_value = '$term_slug'
                    AND products.post_parent = $product->id";
    $variation_id = $wpdb->get_col($query);
    $parent = wp_get_post_parent_id($variation_id[0]);
    if ($parent > 0) {
        $_product = new WC_Product_Variation($variation_id[0]);
        $_currency = get_woocommerce_currency_symbol();
        $stock = $_product->is_in_stock() ? 'instock' : 'out of stock';
        return $term . ' (' . $_product->get_price()  . ' ' . $_currency . ')  -  ' . $stock;
    }
    return $term;
}