pcruvinel/shopify-development

Shopify Development Skill

Use this skill when the user asks about:

• Building Shopify apps or extensions
• Creating checkout/admin/POS UI customizations
• Developing themes with Liquid templating
• Integrating with Shopify GraphQL or REST APIs
• Implementing webhooks or billing
• Working with metafields or Shopify Functions

---

ROUTING: What to Build

IF user wants to integrate external services OR build merchant tools OR charge for features: → Build an App (see references/app-development.md)

IF user wants to customize checkout OR add admin UI OR create POS actions OR implement discount rules: → Build an Extension (see references/extensions.md)

IF user wants to customize storefront design OR modify product/collection pages: → Build a Theme (see references/themes.md)

IF user needs both backend logic AND storefront UI: → Build App + Theme Extension combination

---

Shopify CLI Commands

Install CLI:

npm install -g @shopify/cli@latest

Create and run app:

shopify app init          # Create new app
shopify app dev           # Start dev server with tunnel
shopify app deploy        # Build and upload to Shopify

Generate extension:

shopify app generate extension --type checkout_ui_extension
shopify app generate extension --type admin_action
shopify app generate extension --type admin_block
shopify app generate extension --type pos_ui_extension
shopify app generate extension --type function

Theme development:

shopify theme init        # Create new theme
shopify theme dev         # Start local preview at localhost:9292
shopify theme pull --live # Pull live theme
shopify theme push --development  # Push to dev theme

---

Access Scopes

Configure in shopify.app.toml:

[access_scopes]
scopes = "read_products,write_products,read_orders,write_orders,read_customers"

Common scopes:

• read_products, write_products - Product catalog access
• read_orders, write_orders - Order management
• read_customers, write_customers - Customer data
• read_inventory, write_inventory - Stock levels
• read_fulfillments, write_fulfillments - Order fulfillment

---

GraphQL Patterns (Validated against API 2026-01)

Query Products

query GetProducts($first: Int!, $query: String) {
  products(first: $first, query: $query) {
    edges {
      node {
        id
        title
        handle
        status
        variants(first: 5) {
          edges {
            node {
              id
              price
              inventoryQuantity
            }
          }
        }
      }
    }
    pageInfo {
      hasNextPage
      endCursor
    }
  }
}

Query Orders

query GetOrders($first: Int!) {
  orders(first: $first) {
    edges {
      node {
        id
        name
        createdAt
        displayFinancialStatus
        totalPriceSet {
          shopMoney {
            amount
            currencyCode
          }
        }
      }
    }
  }
}

Set Metafields

mutation SetMetafields($metafields: [MetafieldsSetInput!]!) {
  metafieldsSet(metafields: $metafields) {
    metafields {
      id
      namespace
      key
      value
    }
    userErrors {
      field
      message
    }
  }
}

Variables example:

{
  "metafields": [
    {
      "ownerId": "gid://shopify/Product/123",
      "namespace": "custom",
      "key": "care_instructions",
      "value": "Handle with care",
      "type": "single_line_text_field"
    }
  ]
}

---

Checkout Extension Example

import {
  reactExtension,
  BlockStack,
  TextField,
  Checkbox,
  useApplyAttributeChange,
} from "@shopify/ui-extensions-react/checkout";

export default reactExtension("purchase.checkout.block.render", () => (
  <GiftMessage />
));

function GiftMessage() {
  const [isGift, setIsGift] = useState(false);
  const [message, setMessage] = useState("");
  const applyAttributeChange = useApplyAttributeChange();

  useEffect(() => {
    if (isGift && message) {
      applyAttributeChange({
        type: "updateAttribute",
        key: "gift_message",
        value: message,
      });
    }
  }, [isGift, message]);

  return (
    <BlockStack spacing="loose">
      <Checkbox checked={isGift} onChange={setIsGift}>
        This is a gift
      </Checkbox>
      {isGift && (
        <TextField
          label="Gift Message"
          value={message}
          onChange={setMessage}
          multiline={3}
        />
      )}
    </BlockStack>
  );
}

---

Liquid Template Example

{% comment %} Product Card Snippet {% endcomment %}
<div class="product-card">
  <a href="{{ product.url }}">
    {% if product.featured_image %}
      <img
        src="{{ product.featured_image | img_url: 'medium' }}"
        alt="{{ product.title | escape }}"
        loading="lazy"
      >
    {% endif %}
    <h3>{{ product.title }}</h3>
    <p class="price">{{ product.price | money }}</p>
    {% if product.compare_at_price > product.price %}
      <p class="sale-badge">Sale</p>
    {% endif %}
  </a>
</div>

---

Webhook Configuration

In shopify.app.toml:

[webhooks]
api_version = "2026-01"

[[webhooks.subscriptions]]
topics = ["orders/create", "orders/updated"]
uri = "/webhooks/orders"

[[webhooks.subscriptions]]
topics = ["products/update"]
uri = "/webhooks/products"

# GDPR mandatory webhooks (required for app approval)
[webhooks.privacy_compliance]
customer_data_request_url = "/webhooks/gdpr/data-request"
customer_deletion_url = "/webhooks/gdpr/customer-deletion"
shop_deletion_url = "/webhooks/gdpr/shop-deletion"

---

Best Practices

API Usage

• Use GraphQL over REST for new development
• Request only fields you need (reduces query cost)
• Implement cursor-based pagination with pageInfo.endCursor
• Use bulk operations for processing more than 250 items
• Handle rate limits with exponential backoff

Security

• Store API credentials in environment variables
• Always verify webhook HMAC signatures before processing
• Validate OAuth state parameter to prevent CSRF
• Request minimal access scopes
• Use session tokens for embedded apps

Performance

• Cache API responses when data doesn't change frequently
• Use lazy loading in extensions
• Optimize images in themes using img_url filter
• Monitor GraphQL query costs via response headers

---

Troubleshooting

IF you see rate limit errors: → Implement exponential backoff retry logic → Switch to bulk operations for large datasets → Monitor X-Shopify-Shop-Api-Call-Limit header

IF authentication fails: → Verify the access token is still valid → Check that all required scopes were granted → Ensure OAuth flow completed successfully

IF extension is not appearing: → Verify the extension target is correct → Check that extension is published via shopify app deploy → Confirm the app is installed on the test store

IF webhook is not receiving events: → Verify the webhook URL is publicly accessible → Check HMAC signature validation logic → Review webhook logs in Partner Dashboard

IF GraphQL query fails: → Validate query against schema (use GraphiQL explorer) → Check for deprecated fields in error message → Verify you have required access scopes

---

Reference Files

For detailed implementation guides, read these files:

• references/app-development.md - OAuth authentication flow, GraphQL mutations for products/orders/billing, webhook handlers, billing API integration
• references/extensions.md - Checkout UI components, Admin UI extensions, POS extensions, Shopify Functions for discounts/payment/delivery
• references/themes.md - Liquid syntax reference, theme directory structure, sections and snippets, common patterns

---

Scripts

• scripts/shopify_init.py - Interactive project scaffolding. Run: python scripts/shopify_init.py
• scripts/shopify_graphql.py - GraphQL utilities with query templates, pagination, rate limiting. Import: from shopify_graphql import ShopifyGraphQL

---

Official Documentation Links

• Shopify Developer Docs: https://shopify.dev/docs
• GraphQL Admin API Reference: https://shopify.dev/docs/api/admin-graphql
• Shopify CLI Reference: https://shopify.dev/docs/api/shopify-cli
• Polaris Design System: https://polaris.shopify.com

API Version: 2026-01 (quarterly releases, 12-month deprecation window)