[isaacroldan]

WHY are these changes introduced?

app deploy --no-build with a web pixel extension that was never built fails with a raw filesystem error:

ENOENT: no such file or directory, stat '<extension>/dist/<handle>.js'

buildUIExtension runs the extension's buildValidation before the bundle_ui step checks that the build output exists. The web pixel validation reads the bundle size, so it fails first, and the clear missing-output error never shows.

WHAT is this pull request doing?

When skipBuild is set and the bundle file does not exist, buildUIExtension now throws the same AbortError as the bundle_ui step, before buildValidation runs. The error moves into a MissingBuildOutputError class, so both places print the same message.

Output after the change:

Couldn't find the build output at <extension>/dist/<handle>.js

If you passed --no-build, build the app first. Otherwise check that building the extension produces files at that path.

How to manually test your changes?

1. In an app with a web pixel extension, delete the extension's dist directory.
2. Run shopify app deploy --no-build.
3. Before: the command fails with ENOENT: no such file or directory, stat …. After: it fails with Couldn't find the build output at … and the --no-build hint.

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