Build the delivery options function

In this tutorial, you’ll learn how to do the following tasks:

• Generate starter code for Shopify Functions.
• Use GraphQL to define the input of your function.
• Deploy functions to the Shopify platform.
• Review logs for your function.

• You've created a Partner account.
• You've created a development store.

• You've created an app that uses Shopify CLI 3.49.5 or higher. If you previously installed Shopify CLI, then make sure that you're using the latest version.

  If you plan to create a UI for your extension, then start with the Remix app template.

• You've installed Node.js 16 or higher.

• You've installed your app on the development store.

The following requirements are specific to Rust-based development with Shopify Functions.

• You've installed Rust.

  On Windows, Rust requires the Microsoft C++ Build Tools. Make sure to select the Desktop development with C++ workload when installing the tools.

• You've installed cargo-wasi:

• Delivery customization functions are only applicable to shipping options and aren't compatible with local delivery, local pickup, or pickup points.
• Any changes that you make with Functions aren't applied to Shop Pay checkout.

If you want to quickly get started, then you can get the sample code by completing the following steps. This tutorial describes the sample code step by step.

1. Clone the delivery customizations sample app:

2. Enter a name for your app project.

3. Navigate to your app directory:

4. Link your app configuration:

5. Start a local server for your app:

6. With the server running, open the Preview URL in the terminal output.

   When you open the URL, you're prompted to install the app on your development store.

7. Click Install app to install the app on the store.

8. Create and test your delivery customization.

To create your delivery customization function, you can use Shopify CLI to generate a starter function, specify the inputs for your function using an input query, and implement your function logic using JavaScript or Rust.

1. Navigate to your app directory:

2. Run the following command to create a new delivery customization extension:

3. Choose the language that you want to use. For this tutorial, you should select either Rust or JavaScript.

   If you expect to be working with large payloads of data, Rust is recommended.

4. Navigate to extensions/delivery-customization:

5. Replace the contents of src/run.graphql file with the following code.

   run.graphql defines the input for the function. You need the cart delivery groups, with the delivery state/province code and available delivery options.

   The query differs slightly in Rust and JavaScript due to code generation requirements.

6. If you're using JavaScript, then run the following command to regenerate types based on your input query:

7. Replace the src/run.rs or src/run.js file with the following code.

   This function logic appends a message to all delivery options if the shipping address state or province code is NC. You can adjust this to the state or province of your choice.

To test your function, you need to make it available to your development store.

1. If you're developing a function in a language other than JavaScript or TypeScript, ensure you have configured build.watch in your function extension configuration.

2. Navigate back to your app root:

3. Use the Shopify CLI dev command to start app preview:

   You can keep the preview running as you work on your function. When you make changes to a watched file, Shopify CLI rebuilds your function and updates the function extension's drafts, so you can immediately test your changes.

4. Follow the CLI prompts to preview your app, and install it on your development store.

To activate your function, you must create a delivery customization on the store where you installed your app. You can do this using the deliveryCustomizationCreate GraphQL mutation.

In subsequent tutorials, you'll use metafields on this delivery customization to configure your function, and create a user interface so merchants can configure the function themselves.

1. Install the Shopify GraphiQL app on your store. If you've already installed GraphiQL, then you should do so again to select the necessary access scopes for delivery customizations.

2. In the GraphiQL app, in the API Version field, select the 2023-07 version.

3. Find the ID of your function by executing the following query:

   The result contains a node with your function's ID:

4. Execute the following mutation and replace YOUR_FUNCTION_ID_HERE with the ID of your function:

   You should receive a GraphQL response that includes the ID of the created delivery customization. If the response includes any messages under userErrors, then review the errors, check that your mutation and functionId are correct, and try the request again.

1. From the Shopify admin, go to Settings > Shipping and delivery.

2. Check the Delivery customizations section. You should find the Add message to delivery options for state/province delivery customization that you created with GraphiQL.

3. Open your development store, build a cart, and proceed to checkout.

4. Enter a delivery address that doesn't use the specified state/province code. You shouldn't see any additional messaging on the delivery options.

5. Change your shipping address to use your chosen state/province code. Your delivery options should now have the additional messaging.

6. To debug your function, or view its output, you can review its logs in your Partner Dashboard.

   1. Log in to your Partner Dashboard and navigate to Apps > {your app} > Extensions > delivery-customization.
   2. Click on any function run to view its input, output, and any logs written to STDERR.

• Add configuration to your delivery customization using metafields.