script.liquid

{% if event.preview %}
  {% capture product_json %}
    {
      "handle": "stylish-shirt-503",
      "variants": [
        {
          "sku": "503-L-B",
          "option1": "L",
          "option2": "Black",
          "admin_graphql_api_id": "gid://shopify/ProductVariant/1234567890"
        },
        {
          "sku": "503-XL-G",
          "option1": "XL",
          "option2": "Heather Grey",
          "admin_graphql_api_id": "gid://shopify/ProductVariant/2345678901"
      {% if options.skip_variants_that_already_have_skus__boolean %}
        },
        {
          "option1": "XXL",
          "option2": "Red",
          "admin_graphql_api_id": "gid://shopify/ProductVariant/3456789012"
      {% endif %}
        }
      ],
      "options": [
        {
          "name": "Size"
        },
        {
          "name": "Color"
        }
      ]
    }
  {% endcapture %}

  {% assign product = product_json | parse_json %}
{% endif %}

{% assign allowed_characters = "ABCDEFGHIJKLMNOPQRSTUVWXYZ0123456789" %}

{% assign sku_base = product.handle | split: "-" | last | upcase %}

{% for variant in product.variants %}
  {% if options.skip_variants_that_already_have_skus__boolean and variant.sku != blank %}
    {% log message: "variant already has a sku; skipping", original_sku: variant.sku %}
    {% continue %}
  {% endif %}

  {% assign variant_sku_generated = sku_base %}

  {% assign variant_options = array %}
  {% assign variant_options[0] = variant.option1 %}
  {% assign variant_options[1] = variant.option2 %}
  {% assign variant_options[2] = variant.option3 %}

  {% assign variant_option_names = product.options | map: "name" %}

  {% for variant_option in variant_options %}
    {% if variant_option == blank %}
      {% continue %}
    {% endif %}

    {% if options.product_options_to_keep_unabbreviated__array contains variant_option_names[forloop.index0] %}
      {% assign variant_sku_generated = variant_sku_generated | append: "-" | append: variant_option %}
    {% else %}
      {% assign variant_option_abbreviation = "" %}
      {% assign variant_option_characters = variant_option | split: "" %}
      {% for variant_option_character in variant_option_characters %}
        {% if allowed_characters contains variant_option_character %}
          {% assign variant_option_abbreviation = variant_option_abbreviation | append: variant_option_character %}
        {% endif %}
      {% endfor %}

      {% if variant_option_abbreviation == blank %}
        {% assign variant_option_abbreviation = variant_option_characters[0] | upcase %}
      {% endif %}

      {% assign variant_sku_generated = variant_sku_generated | append: "-" | append: variant_option_abbreviation %}
    {% endif %}
  {% endfor %}

  {% if variant_sku_generated != variant.sku %}
    {% log message: "updating sku", original_sku: variant.sku, generated_sku: variant_sku_generated %}

    {% comment %}
      -- update skus on inventory items, as this is no longer supported on variants as of 2024-07 API
    {% endcomment %}

    {% action "shopify" %}
      mutation {
        inventoryItemUpdate(
          id: {{ variant.inventory_item.admin_graphql_api_id | json }}
          input: {
            sku: {{ variant_sku_generated | json }}
          }
        ) {
          inventoryItem {
            variant {
              id
              displayName
              sku
            }
          }
          userErrors {
            field
            message
          }
        }
      }
    {% endaction %}
  {% endif %}
{% endfor %}