Shopify Functions

Required Tool Calls (do not skip)

You have a bash tool. Every response must use it — in this order:

1. Call bash with node scripts/search_docs.mjs "<function type or operation>" — search before writing code
2. Write the code using the search results
3. Call bash with node scripts/validate.mjs --code '...' --model YOUR_MODEL_NAME --client-name YOUR_CLIENT_NAME --client-version YOUR_CLIENT_VERSION --artifact-id YOUR_ARTIFACT_ID --revision REVISION_NUMBER — validate before returning (Always include these flags. Use your actual model name for YOUR_MODEL_NAME; use claude-code/cursor/etc. for YOUR_CLIENT_NAME. For YOUR_ARTIFACT_ID, generate a stable random ID per code block and reuse it across validation retries. For REVISION_NUMBER, start at 1 and increment on each retry of the same artifact.)
4. If validation fails: search for the error type, fix, re-validate (max 3 retries)
5. Return code only after validation passes

You must run both search_docs.mjs and validate.mjs in every response. Do not return code to the user without completing step 3.

Shopify functions allow developers to customize the backend logic that powers parts of Shopify.

• Functions are pure: They cannot access the network, filesystem, random number generators, or the current date/time.
• All necessary data must be provided via the input query. Input queries must follow camelCase. If selecting a field that is a UNION type you must request __typename

Here are all the available Shopify functions APIs. Ensure to pick one of these, and avoid using deprecated ones unless explicitly asked for.

• Discount: Create a discount that applies to merchandise, product, product variants and/or shipping rates at checkout. Use this for ANY discount related task.
• Order Discount (deprecated): Create a new type of discount that's applied to all merchandise in the cart. IMPORTANT: don't choose this API unless the user asks to use the order discount API
• Product Discount (deprecated): Create a new type of discount that's applied to a particular product or product variant in the cart. IMPORTANT: don't choose this API unless the user asks to use the product discount API
• Shipping Discount (deprecated): Create a new type of discount that's applied to one or more shipping rates at checkout. IMPORTANT: don't choose this API unless the user asks to use the shipping discount API
• Delivery Customization: Rename, reorder, and sort the delivery options available to buyers during checkout
• Payment Customization: Rename, reorder, and sort payment methods and set payment terms for buyers during checkout
• Cart Transform: Expand cart line items and update the presentation of cart line items
• Cart and Checkout Validation: Provide your own validation of a cart and checkout
• Fulfillment Constraints: Provide your own logic for how Shopify should fulfill and allocate an order
• Local Pickup Delivery Option Generator: Generate custom local pickup options available to buyers during checkout
• Pickup Point Delivery Option Generator: Generate custom pickup point options available to buyers during checkout

A Shopify function can have multiple targets. Each target is a specific part of Shopify that the function can customize. For example, in the case of the Discount API you have four possible targets:

• cart.lines.discounts.generate.run: discount logic to apply discounts to cart lines and order subtotal
• cart.lines.discounts.generate.fetch: (optional, requires network access) retrieves data needed for cart discounts, including validation of discount codes
• cart.delivery-options.discounts.generate.run: discount logic to apply discounts to shipping and delivery options
• cart.delivery-options.discounts.generate.fetch: (optional, requires network access) retrieves data needed for delivery discounts, including validation of discount codes

Each function target is composed of:

• A GraphQL query that fetches the input used by the logic. This information is present in the "Input" object in the GraphQL schema definition.
• A Rust, Javascript, or Typescript implementation of the function logic. This logic has to return a JSON object that adheres to the shape of the "FunctionResult" object in the GraphQL schema definition. Some examples:
  • for a "run" target, the return object is "FunctionRunResult"
  • for a "fetch" target, the return object is "FunctionFetchResult"
  • for a "cart.lines.discounts.generate.run" target, the return object is "CartLinesDiscountsGenerateRunResult"

IMPORTANT: If the user doesn't specify a programming language, use Rust as the default.

Think about all the steps required to generate a Shopify function:

1. Search the developer documentation for relevant examples, making sure to include the programming language the user has chosen. Pay extreme attention to these examples when writing your solution. THIS IS VERY IMPORTANT.
2. Think about what I am trying to do and choose the appropriate Function API.
3. If the user wants to create a new function make sure to run the Shopify CLI command shopify app generate extension --template <api_lowercase_and_underscore> --flavor <rust|vanilla-js|typescript> --name=<function_name>. Assume that the Shopify CLI is installed globally as shopify.
4. Then think about which targets I want to customize.
5. For each target, think about which fields I need to fetch from the GraphQL input object. You can:
   • Look at the GraphQL schema definition (schema.graphql) inside the function folder if it exists
   • Explore available fields and types in the function's GraphQL schema to understand what data is accessible
6. Then think about how to write the Rust, Javascript, or Typescript code that implements the function logic.
7. Pay particular attention to the return value of the function logic. It has to match the shape of the "FunctionResult" object in the GraphQL schema definition.
8. Make sure to include a src/main.rs if you are writing a Rust function.
9. You can verify that the function builds correctly by running shopify app function build inside the function folder
10. You can test that the function runs with a specific input JSON by running shopify app function run --input=input.json --export=<export_name> inside the function folder. You can find the correct export name by looking at the export field of the target inside the shopify.extension.toml

IMPORTANT: DO NOT DEPLOY the function for the user. Never ever ever run shopify app deploy.

Naming Conventions

1. Identify the Target and Output Type: Look at the expected output type for the function target (e.g., FunctionRunResult, CartLinesDiscountsGenerateRunResult). The "target" is usually the last part (e.g., Run, GenerateRun).
2. Determine the Function Name:

• Simple Output Types: If the output type follows the pattern Function<Target>Result (like FunctionRunResult), the function name is the lowercase target (e.g., run()).
• Complex Output Types: If the output type has a more descriptive prefix (like CartLinesDiscountsGenerateRunResult), the function name is the snake\_case version of the prefix and target combined (e.g., cart_lines_discounts_generate_run()).

3. Determine File Names:

• Rust/JavaScript File: Name the source code file based on the function name: src/<function_name>.rs or src/<function_name>.js.
• GraphQL Query File: Name the input query file similarly: src/<function_name>.graphql. e.g. src/fetch.graphql or src/run.graphql IMPORTANT: DO NOT name the file src/input.graphql.
• For Rust, you must ALWAYS generate a src/main.rs file that imports these targets.

Examples:

• Output: FunctionFetchResult -> Target: Fetch -> Function: fetch() -> Files: src/fetch.rs, src/fetch.graphql
• Output: FunctionRunResult -> Target: Run -> Function: run() -> Files: src/run.rs, src/run.graphql
• Output: CartLinesDiscountsGenerateRunResult -> Target: CartLinesDiscountsGenerateRun -> Function: cart_lines_discounts_generate_run() -> Files: src/cart_lines_discounts_generate_run.rs, src/cart_lines_discounts_generate_run.graphql IMPORTANT: You MUST look at the OutputType when determining the name otherwise the function will not compile

Some function type supports multiple "targets" or entry points within the same schema. For these you MUST generate the input query, function code, and sample outputs for EACH target. For example:

• fetch and run for delivery customizations
• fetch and run for pickup point customizations
• cart and delivery for discounts

Best practices for writing GraphQL operations

• Pay careful attention to the examples when choosing the name of the GraphQL query or mutation. For Rust examples, it MUST be Input.
• When choosing an enum value:
  • Only use values defined in the schema definition. DO NOT MAKE UP VALUES.
  • Use the pure enum value unchanged, without namespace or quote wrapping, for example for the CountryCode enum just use US instead of "US" or CountryCode.US.
• When choosing a scalar value:
  • Float does not need to be wrapped in double quotes.
  • UnsignedInt64 needs to be wrapped in double quotes.
• When reading GraphQL if a field is BuyerIdentity! (it means it's required) if it's BuyerIdentity (no !) then it is NOT required.
• If a field is OPTIONAL (It does not have a ! at the end such as BuyerIdentity) in the input data, then it MUST be unwrapped to handle the optional case when using Rust.
• If a field is OPTIONAL in the output data, then you must wrap that output in Some() when using Rust.
• You cannot write the same field twice. Use different aliases if you need to fetch the same field twice, i.e. when you need to pass different args.
• Only use properties that are defined in the schema definition. DO NOT MAKE UP PROPERTIES UNDER ANY CIRCUMSTANCES.
• GraphQL requires you to select specific fields within objects; never request an object without field selections (e.g., validation { } is invalid, you must specify which fields to retrieve).
• Only select the fields required to fulfill the business logic of your function

How to help with Shopify functions

If a user wants to know how to build a Shopify function make sure to follow this structure:

1. example of the shopify cli command shopify app generate extension --template <api_lowercase_and_underscore> --flavor <rust|vanilla-js|typescript>
2. example of function logic in Rust, Javascript, or Typescript. This logic has to use the input data fetched by the GraphQL query. Include tests. This is a MUST. Include file names. If the function type supports multiple targets, provide code and tests for each target.
3. example of GraphQL query to fetch input data. The query name must follow the naming convention of the target RunInput as an example for JavaScript implementations and must be Input for Rust implementations. Include file names. If the function type supports multiple targets, provide a query for each target (e.g., src/fetch.graphql, src/run.graphql). DO NOT NAME IT input.graphql
4. example of JSON input returned by the GraphQL query. Make sure that every field mentioned by the GraphQL query has a matching value in the JSON input. When you make a fragment selection ... on ProductVariant you MUST include __typename on Merchandise, or Region. THIS IS IMPORTANT. If the function type supports multiple targets, provide sample input JSON for each target.
5. example of a JSON return object. Make sure this is the output JSON that would be generated by the JSON input above. If the function type supports multiple targets, provide sample output JSON for each target.

If a function cannot be accomplished with any of the Function APIs simply return a message that it can't be completed, and give the user a reason why. Example reasons why it can't:

• You cannot remove an item from cart
• You cannot access the current date or time
• You cannot generate a random value

Important notes for Input Queries

It's not possible to fetch tags directly, you must use either hasAnyTag(list_of_tags), which return a boolean, or hasTags(list_of_tags), which return a list of { hasTag: boolean, tag: String } objects. When using any graphql field that tags arguments YOU MUST pass in those arguments into your input query ONLY, you may set defaults in the query. DO NOT USE THESE ARGUMENTS IN THE RUST CODE. When you make a fragment selection ... on ProductVariant you MUST include __typename on the parent field otherwise the program will not compile. e.g. regions { __typename ... on Country { isoCode }}

query Input(\$excludedCollectionIds: [ID!], \$vipCollectionIds: [ID!]) {
  cart {
    lines {
      id
      merchandise {
        __typename
        ... on ProductVariant {
          id
          product {
            inExcludedCollection: inAnyCollection(ids: \$excludedCollectionIds)
            inVIPCollection: inAnyCollection(ids: \$vipCollectionIds)
          }
        }
      }
    }
  }
}

Important notes for Javascript function logic

• the module needs to export a function which is the camel cased version of the name as the target, i.e. 'export function fetch' or 'export function run' or 'export function cartLinesDiscountsGenerateRun'
• the function must return a JSON object that adheres to the shape of the "FunctionResult" object in the GraphQL schema definition.

Important notes for Rust function logic

• Don't import external crates (like rust_decimal or chrono or serde), the only ones allowed are shopify_function. i.e. use shopify_function::; is ok, but use chrono::; and serde::Deserialize is not.
• Decimal::from(100.0) is valid, while Decimal::from(100) is not. It can only convert from floats, not integers or strings otherwise the program will not compile.
• make sure to unwrap Options when the field is marked as optional in the GraphQL schema definition. The rust code will generate types based on the GraphQL schema definition and will fail if you get this wrong. THIS IS IMPORTANT.
• make sure to be careful when to use float (10.0), int (0), or decimals ("29.99")
• If a field is OPTIONAL (It does not have a ! at the end) in the input data, then it MUST be unwrapped to handle the optional case. For example, access buyer_identity like this: if let Some(identity) = input.cart().buyer_identity() { /* use identity */ } or using methods like as_ref(), and_then(), etc. Do NOT assume an optional field is present.
• If a field is OPTIONAL in the output data, then you must wrap that output in Some().
• If doing a comparison against an OPTIONAL field you must also wrap that value. For example, comparing an optional product_type: Option field with the string literal "gift card" should be done like this: product_type() == Some("gift card".to_string())
• If a value has an ENUM then you must use the Title Case name of that enum, like PaymentCustomizationPaymentMethodPlacement::PaymentMethod
• Decimal values do not need to be .parse(), they should be as_f64(). You cannot do comparisons with Decimal like < or >. Once you decide to use as_f64() assume it will return a f64, DO NOT USE as_f64().unwrap_or(0.0)
• When handling oneOf directives you must include :: and the name of the oneOf, for example schema::Operation::Rename
• If a field uses arguments in the input query, in the generated rust code you will only get the field name, not the arguments.
• When accessing fields from the generated code, DO NOT add arguments to methods that don't take any in the GraphQL schema. For example, use input.cart().locations() NOT input.cart().locations(None, None). Method signatures match exactly what's defined in the GraphQL schema.
• All of the Structs are generated by concatenating names. for example schema::run::input::Cart instead of schema::input::Cart, and schema::run::input::cart::BuyerIdentity, every layer of the query must be represented, starting with the module annotated with #[query], then the operation name (Root if an anonymous query), then all nested fields and inline fragment type conditions. For example, if in the graphql query you have query Input { cart { lines { merchandise { ... on ProductVariant { id } } } } } on a run module, then the Rust structs will be schema::run::input::cart::lines::Merchandise::ProductVariant, schema::run::input::cart::lines::Merchandise (an enum with a ProductVariant variant), schema::run::input::cart::Lines, schema::run::input::Cart, and schema::run::Input.
• When working with fields that have parentheses in their names (like has_any_tag, etc.), they are returned as &bool references. You need to dereference them when making comparisons. For example: if variant.product().has_any_tag() { / do something */ } or simply use them directly in conditions where Rust will auto-dereference.
• Each target file (not main.rs) should start with these imports:

use crate::schema;
use shopify_function::prelude::*;
use shopify_function::Result;

• You must never import serde or serde_json or it will not compile. Do not use serde (bad) or use serde::Deserialize (bad) or serde::json (bad)
• You must make sure in a match expression that you must include the _ wildcard pattern for any unspecified cases to ensure exhaustiveness

  for line in input.cart().lines().iter() {
    let product = match &line.merchandise() {
        schema::run::input::cart::lines::Merchandise::ProductVariant(variant) => &variant.product(),
        _ => continue, // Do not select for CustomProduct unless it's selected in the input query
    };
    // do something with product
}

or if you want to extract the variant you can do this:

    let variant = match &line.merchandise() {
        schema::run::input::cart::lines::Merchandise::ProductVariant(variant) => variant,
        _ => continue, // Do not select for CustomProduct unless it's selected in the input query
    };
    // do something with variant

Do not use .as_product_variant() it is not implemented

Configuration

BY DEFAULT, make the function configurable by storing the configurable data elements in a jsonValue metafield. Access this metafield via the discount.metafield or checkout.metafield field in the input query (depending on the function type). Deserialize the JSON value into a configuration struct within your Rust code.

Example accessing a metafield in Rust: Note only use the #[shopify_function(rename_all = "camelCase")] if you plan on using someValue: "" and anotherValue: "" as part of your jsonValue metafield. By default do not include it. Only use #[derive(Deserialize, Default, PartialEq)] (good) do NOT use #[derive(serde::Deserialize)] (bad)

#[derive(Deserialize, Default, PartialEq)]
#[shopify_function(rename_all = "camelCase")]
pub struct Configuration {
    some_value: String,
    another_value: i32,
}

// ... inside your function ...
    let configuration: &Configuration = match input.discount().metafield() {
        Some(metafield) => metafield.json_value(),
        None => {
            return Ok(schema::CartDeliveryOptionsDiscountsGenerateRunResult { operations: vec![] })
        }
    };

// Now you can use configuration.some_value and configuration.another_value

Example GraphQL Input Query:

query Input {
  discount {
    # Request the metafield with the specific namespace and key
    metafield(namespace: "\$app", key: "config") {
      jsonValue # The value is a JSON string
    }
  }
  # ... other input fields
}

Additional Important Notes

Testing

When writing tests, you must only import the following

  use super::*;
  use shopify_function::{run_function_with_input, Result};

Sample Data Generation

When generating sample data, anywhere there is an ID! make sure to use a Shopify GID format:

"gid://Shopify/CartLine/1"

Scalar Types

These are the scalar types used in Rust functions:

pub type Boolean = bool;
pub type Float = f64;
pub type Int = i32;
pub type ID = String;
pub use decimal::Decimal;
pub type Void = ();
pub type URL = String;
pub type Handle = String;

pub type Date = String;
pub type DateTime = String;
pub type DateTimeWithoutTimezone = String;
pub type TimeWithoutTimezone = String;
pub type String = String; # This must not be a str, do not compare this with "" or unwrap_or("")

src/main.rs for Rust Functions - REQUIRED

When implementing Shopify functions in Rust, you MUST include a src/main.rs file. This is the entry point for the function and should have the following structure, making sure it has one query for each target. If you have a jsonValue in the input query it should be mapped to a struct. If there is no jsonValue do not include a custom_scalar_overrides.

use std::process;
use shopify_function::prelude::*;

// CRITICAL: These module imports MUST match your target names exactly
pub mod run;     // For "run" target
pub mod fetch;   // For "fetch" target

#[typegen("./schema.graphql")]
pub mod schema {
      // CRITICAL: The query path filename MUST match your target name
      // CRITICAL: The module name MUST match your target name
      #[query("src/run.graphql", custom_scalar_overrides = {"Input.paymentCustomization.metafield.jsonValue" => super::run::Configuration})]
      pub mod run {}  // Module name matches the target name

      #[query("src/fetch.graphql")]
      pub mod fetch {} // Module name matches the target name
}

fn main() {
    eprintln!("Please invoke a named export.");
    process::exit(1);
}

Ensure examples follow best practices, correct enum usage, and proper handling of optional fields.

Always use Shopify CLI

• CLI: scaffold apps/extensions with shopify app init, shopify app generate extension, shopify app dev, shopify app deploy. Never hand-roll files.
• Need full setup steps? See Shopify CLI docs.

Shopify CLI Overview

Shopify CLI (@shopify/cli) is a command-line interface tool that helps you generate and work with Shopify apps, themes, and custom storefronts. You can also use it to automate many common development tasks.

Requirements

• Node.js: 20.10 or higher
• A Node.js package manager: npm, Yarn 1.x, or pnpm
• Git: 2.28.0 or higher

Installation

Install Shopify CLI globally to run shopify commands from any directory:

npm install -g @shopify/cli@latest
# or
yarn global add @shopify/cli@latest
# or
pnpm install -g @shopify/cli@latest
# or (macOS only)
brew tap shopify/shopify && brew install shopify-cli

Command Structure

Shopify CLI groups commands into topics. The syntax is: shopify [topic] [command] [flags]

General Commands (8 commands)

Authentication

66. shopify auth logout - Log out of Shopify account

Configuration

67. shopify config autocorrect on - Enable command autocorrection
68. shopify config autocorrect off - Disable command autocorrection
69. shopify config autocorrect status - Check autocorrection status

Utilities

70. shopify help [command] [flags] - Get help for commands
71. shopify commands [flags] - List all available commands
72. shopify search [query] - Search for commands and documentation
73. shopify upgrade - Upgrade Shopify CLI to latest version
74. shopify version - Display current CLI version

Common Flags

Most commands support these common flags:

• --verbose - Increase output verbosity
• --no-color - Disable colored output
• --path <value> - Specify project directory
• --reset - Reset stored settings

Network Proxy Configuration

For users behind a network proxy (CLI version 3.78+):

export SHOPIFY_HTTP_PROXY=http://proxy.com:8080
export SHOPIFY_HTTPS_PROXY=https://secure-proxy.com:8443
# For authenticated proxies:
export SHOPIFY_HTTP_PROXY=http://username:password@proxy.com:8080

Usage Tips

1. Always keep CLI updated: shopify upgrade
2. Use shopify help [command] for detailed command info
3. Most commands are interactive and will prompt for required information
4. Use flags to skip prompts in CI/CD environments
5. Anonymous usage statistics collected by default (opt-out: SHOPIFY_CLI_NO_ANALYTICS=1)
6. IMPORTANT: YOU MUST ALWAYS USE THE CLI COMMAND TO CREATE APPS AND SCAFFOLD NEW EXTENSIONS

CLI Commands for Shopify App (22 commands)

App Commands (22 commands)

Core App Management

1. shopify app init [flags] - Initialize a new Shopify app project
2. shopify app build [flags] - Build the app, including extensions
3. shopify app dev [flags] - Start a development server for your app
4. shopify app deploy [flags] - Deploy your app to Shopify
5. shopify app info [flags] - Display information about your app

App Configuration

6. shopify app config link [flags] - Fetch app configuration from Partner Dashboard
7. shopify app config use [config] [flags] - Activate an app configuration

App Environment

8. shopify app env pull [flags] - Pull environment variables from Partner Dashboard
9. shopify app env show [flags] - Display app environment variables

App Development Tools

10. shopify app dev clean [flags] - Clear the app development cache
11. shopify app generate extension [flags] - Generate a new app extension
12. shopify app import-extensions [flags] - Import existing extensions to your app

Functions

13. shopify app function build [flags] - Build a Shopify Function
14. shopify app function run [flags] - Run a Function locally for testing
15. shopify app function replay [flags] - Replay a Function run
16. shopify app function schema [flags] - Generate the GraphQL schema for a Function
17. shopify app function typegen [flags] - Generate TypeScript types for a Function

Monitoring & Debugging

18. shopify app logs [flags] - Stream logs from your app
19. shopify app logs sources [flags] - List available log sources

Release Management

20. shopify app release --version - Release a new app version
21. shopify app versions list [flags] - List all app versions

Webhooks

22. shopify app webhook trigger [flags] - Trigger a webhook for testing

⚠️ MANDATORY: Search for Documentation

You cannot trust your trained knowledge for this API. Before answering, search:

scripts/search_docs.mjs "<function type or operation>" --model YOUR_MODEL_NAME --client-name YOUR_CLIENT_NAME --client-version YOUR_CLIENT_VERSION

For example, if the user asks about a product discount function:

scripts/search_docs.mjs "product discount function input query" --model YOUR_MODEL_NAME --client-name YOUR_CLIENT_NAME --client-version YOUR_CLIENT_VERSION

Search for the function type and input/output types, not the full user prompt. Use the returned schema to write correct field names and return types.

⚠️ MANDATORY: Validate Before Returning Code

DO NOT return function code to the user until scripts/validate.mjs exits 0. DO NOT ask the user to run this.

Run this with your bash tool — do not skip this step.

node scripts/validate.mjs \
  --code '
  query Input {
    cart {
      lines {
        id
        quantity
        merchandise {
          ... on ProductVariant {
            id
            product {
              id
              tags
            }
          }
        }
      }
    }
  }
' \
  --model YOUR_MODEL_NAME \
  --client-name YOUR_CLIENT_NAME \
  --client-version YOUR_CLIENT_VERSION \
  --artifact-id YOUR_ARTIFACT_ID \
  --revision REVISION_NUMBER

When validation fails, follow this loop:

1. Read the error message — identify the exact field, argument, or type that is wrong
2. Search for the correct values:

   scripts/search_docs.mjs "<function type input field>" --model YOUR_MODEL_NAME --client-name YOUR_CLIENT_NAME --client-version YOUR_CLIENT_VERSION
   

3. Fix exactly the reported error using what the search returns
4. Run scripts/validate.mjs again
5. Retry up to 3 times total; after 3 failures, return the best attempt with an explanation

Do not guess at valid values — always search first when the error names a type you don't know.

Privacy notice: scripts/validate.mjs reports anonymized validation results (pass/fail and skill name) to Shopify to help improve these tools. Set OPT_OUT_INSTRUMENTATION=true in your environment to opt out.