Rust support in Shopify Functions

You can write your functions in Rust. This guide describes the Rust crate that Shopify provides to help developers build with Shopify Functions.

Requirements

Anchor link to section titled "Requirements"

You need to have graphql_client installed as a dependency in your project:

How it works

Anchor link to section titled "How it works"

Rust crate bundles graphql_client-based type generation, reduces boilerplate code, and makes it easier to unit testing various function inputs. Rust crate includes the following components:

Component	Description
`generate_types`	A macro that enables you to do the following: Generate structs based on your input query. Generate output and response types for the current Function API, based on the provided schema. Automatically generate an `.output.graphql` file for code generation purposes. You can add this file to your `.gitignore` file.
`shopify_function`	An attribute macro that marks the following function as the entry point for a function. It manages the function's `STDIN` input parsing and `STDOUT` output serialization for you.
`run_function_with_input`	A utility for unit testing that enables you to add new tests based on a given JSON input string.

Viewing the generated types

Anchor link to section titled "Viewing the generated types"

To preview the types generated by the generate_types macro, use the cargo doc command.

You can also use the cargo-expand crate to view the generated source, or use the rust-analyzer VSCode extension to get IntelliSense for Rust and the generated types.

Example implementation

Anchor link to section titled "Example implementation"

Explore an example implementation of Shopify Function Rust crate.

Shopify Rust function example

Explore an example of how to use the Shopify Function Rust crate to write a function.

Update an existing function

Anchor link to section titled "Update an existing function"

You can update an existing function written in Rust to use the shopify_function attribute:

In your project, run cargo add shopify_function.
Run cargo add graphql_client@0.12.0.
Delete src/api.rs.

In main.rs, complete the following steps:

Add imports for shopify_function:
Remove references to mod api.
Add type generation directly under your imports:
Remove the main function entirely.
Attribute the function function with the shopify_function macro, and change its return type:

Update the types and fields utilized in the function to the new, auto-generated structs. The following table provides an example:

Old	New
`input::Input`	`input::ResponseData`
`input::Metafield`	`input::InputDiscountNodeMetafield`
`input::DiscountNode`	`input::InputDiscountNode`
`FunctionResult`	`output::FunctionResult`
`DiscountApplicationStrategy::First`	`output::DiscountApplicationStrategy::FIRST`

Add .output.graphql to your .gitignore file.

Next steps

Anchor link to section titled "Next steps"

Explore the reference documentation for crate shopify_function.