Normalize paths in bundle-ui-step same-path guard

[vctrchu]

Resolves https://github.com/shop/issues-retail/issues/28335

Companion ui-extension PR

Summary

shopify app build intermittently fails on UI extensions with:

The same-path guard in bundle-ui-step.ts compared localOutputDir and bundleOutputDir as raw strings. These are computed along different code paths:

• localOutputDir = dirname(buildUIExtension(...)) — where esbuild writes
• bundleOutputDir = dirname(extension.outputPath) or joinPath(dirname(extension.outputPath), bundleFolder) — copy destination

When both resolve to the same directory on disk but differ as strings (a . segment, a trailing slash, a path that went through a different joinPath path and came out non-canonical), the !== check slips through and fs-extra rejects the copy.

Fix

Normalize both sides with resolvePath before comparing:

-if (localOutputDir !== bundleOutputDir) {
+if (resolvePath(localOutputDir) !== resolvePath(bundleOutputDir)) {
   await copyFile(localOutputDir, bundleOutputDir)
 }

Two-line change. Same code path that the existing test at bundle-ui-step.test.ts:38-47 was already asserting skips the copy — the guard just wasn't robust to non-canonical path shapes.

Scope

• Pure guard normalization. copyFile is only invoked in the "different directories" case (unchanged).
• No behavior change when the two directories are genuinely different — resolvePath is idempotent on canonical paths.
• No runtime-resolution of symlinks (keeps current semantics — we rely on string equality of resolved paths, not realpathSync).

How to reproduce on main

Any local setup where extension.outputPath and buildUIExtension's return value compute to the same directory via different string shapes will hit this. It surfaced for me while running pnpm shopify app build --path <sibling-app> against a test extension that links @shopify/ui-extensions via a pnpm.overrides link: path — the esbuild output path came back in a different normalization from the extension output path, and the existing guard missed it.

Test plan

• Existing bundle-ui-step.test.ts still passes (unit test mocks fs.copyFile; the behavior asserted — "skips the copy when local and bundle output directories are identical" — is preserved and now more robust).
• Full shopify app build on an affected extension completes end-to-end (previously failed at the bundle step).
• Reviewer: any path shape that was previously distinct-by-string-comparison but resolvePath-equal would now skip the copy. Confirm no intended code path relied on that (I could not find one — the branch is explicitly guarding against fs-extra's same-path rejection, and every caller I traced expects a no-op when the dirs collapse).

Rollback

Revert the two-line change. No migration required.

[Copilot]

Pull request overview

Fixes an intermittent shopify app build failure for UI extensions where the “same-path” copy guard in the bundle UI build step could miss equivalent paths that differ only by non-canonical string shape (e.g., . segments), causing fs-extra to throw “Source and destination must not be the same.”

Changes:

• Normalize localOutputDir and bundleOutputDir via resolvePath before comparing, preventing same-path copy attempts.
• Add a changeset documenting the patch release and the failure mode addressed.

Reviewed changes

Copilot reviewed 2 out of 2 changed files in this pull request and generated 1 comment.

File	Description
packages/app/src/cli/services/build/steps/bundle-ui-step.ts	Normalizes both directories before the same-path guard comparison to avoid same-path copy errors.
.changeset/fix-bundle-ui-step-path-normalization.md	Declares a patch release for @shopify/app and documents the fix.

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