Check JavaScript function prepare variables against the run query on deploy

[saga-dasgupta]

WHY?

A function's prepare target returns variables for its run target's input query. For JavaScript functions, nothing checks these before the function runs:

• the generated type for variables is unknown;
• at run time, a misspelled key is dropped and the variable silently falls back to its default.

This PR catches those mistakes at deploy, and the developer can't skip the check.

WHAT is this pull request doing?

The check handles each .prepare target that has an export:

1. It takes the matching .run target's input query and builds its variable definitions against the function's schema.graphql.
2. It uses the TypeScript checker to follow what the export returns back to where it's built, through local helpers, conditionals, ??/|| and re-exports.
3. It reports:
   • keys the query doesn't declare;
   • missing required variables;
   • wrong types, including enum values, list elements and input object fields;
   • null or undefined where the variable can't take them.

Where it runs. The check is called from the function spec's preDeployValidation, for JavaScript functions only. That runs before the upload on every deploy.

Example output:

The function extension "delivery-customization" returns prepare variables its run query doesn't accept
src/cart_delivery_options_transform_prepare.js:23:23 `variables.rulehandle` isn't declared by src/cart_delivery_options_transform_run.graphql

How to manually test your changes?

1. In an app with a JavaScript function that has .prepare and .run targets, misspell a key under variables in what the prepare export returns.
2. Run shopify app deploy from a /snapit build. It stops at "Running validation", names the file, line and key, and doesn't create a version.
3. Fix the key and deploy again. Validation passes.

Checklist

• I've considered possible cross-platform impacts (Mac, Linux, Windows)
• I've considered possible documentation changes
• I've considered analytics changes to measure impact
• The change is user-facing — I've identified the correct bump type (patch for bug fixes · minor for new features · major for breaking changes) and added a changeset with pnpm changeset add

[saga-dasgupta]

/snapit

[github-actions]

🫰✨ Thanks @saga-dasgupta! Your snapshot has been published to npm.

Built from a22f4cac9a3143405e041d7877601c00b1868708. Workflow run.

Test the snapshot by installing your package globally:

pnpm i -g --@shopify:registry=https://registry.npmjs.org @shopify/cli@0.0.0-snapshot-20261008004212

Caution

After installing, validate the version by running shopify version in your terminal.
If the versions don't match, you might have multiple global instances installed.
Use which shopify to find out which one you are running and uninstall it.