feat(workerEntry): backfill regionId in segment from cf-region-code

[JonasJesus42]

Summary

Follow-up to #209. Makes the location-matcher fix work for existing storefronts without any worker-entry edit — they only need to bump the package.

Today, after #209 merged, sites still hit a cache contamination bug:

1. Visitor in RJ opens / → matcher resolves the RJ variant correctly → response cached with key desktop
2. Visitor in SP opens / → cache HIT on same desktop key → receives the RJ variant
3. No one in SP sees the right variant until TTL expires

The matcher is correct, but the cache key doesn't include region. To fix that today, every storefront has to edit src/worker-entry.ts:

 buildSegment: (request) => {
   const vtx = extractVtexContext(request);
+  const cf = (request as unknown as { cf?: { regionCode?: string } }).cf;
+  const geoRegion = request.headers.get("cf-region-code") ?? cf?.regionCode ?? "";
   return {
     device: ...,
     ...
-    regionId: (vtx as any).regionId ?? undefined,
+    regionId: (vtx as any).regionId ?? (geoRegion || undefined),
   };
 },

That's friction at every storefront. This PR moves the backfill into createDecoWorkerEntry so the bump alone is enough.

Change

createDecoWorkerEntry now wraps the consumer's buildSegment. If the returned segment is missing regionId, the framework injects it from cf-region-code (header first, then request.cf).

const buildSegment = rawBuildSegment
  ? (request) => {
      const seg = rawBuildSegment(request);
      if (seg.regionId) return seg;
      const region = readRegionFromRequest(request);
      return region ? { ...seg, regionId: region } : seg;
    }
  : undefined;

Compatibility

• Sites that set regionId explicitly (e.g. VTEX regionalization) → unchanged. Wrapper is a no-op when seg.regionId is truthy.
• Sites that don't pass buildSegment at all → unchanged. Backfill only applies when the consumer opted in to segmentation.
• Sites that previously returned regionId: undefined → now get it from CF. The cache key gains a r=<region> segment. One-time cache miss spike on first deploy after the bump, then stable.

Why split from #209

#209 was the matcher logic + migration template default. This is a separate, narrowly-scoped runtime change to workerEntry. Keeping it separate makes it easier to revert if any site sees an unexpected regression.

Test plan

• npm run typecheck
• Full vitest suite (28 tests in workerEntry/builtins area unchanged)
• Validate on [PREVIEW — DO NOT MERGE] Location matcher segmentation demo deco-sites/storefront-tanstack#9 preview: drop the local matcher override in the storefront, bump to this release, confirm variant still resolves per region

Refs #209

🤖 Generated with Claude Code

---

Summary by cubic

Automatically backfills segment.regionId from Cloudflare geo inside createDecoWorkerEntry, preferring request.cf.regionCode and falling back to cf-region-code. Cache keys become region-aware without editing storefront worker-entry.ts, preventing cross-region cache contamination. Bumping @decocms/start is enough.

• Bug Fixes
  • Wraps consumer buildSegment; if regionId is missing, sets it from request.cf.regionCode first, then cf-region-code header.
  • No-op when regionId is already set or when no buildSegment is provided.
  • One-time cache miss spike expected as the key now includes region.

^{Written for commit 044724c. Summary will update on new commits.}

[cubic-dev-ai]

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[github-actions]

🎉 This PR is included in version 6.4.0 🎉

The release is available on:

• v6.4.0
• GitHub release

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