fix(build): make vinext shim chunk rule reachable for installed copies

[Jbithell]

Closes #2794

Problem

createClientManualChunks in src/build/client-build-config.ts returns early
for every module id containing node_modules. For an installed copy of vinext,
its own client shims live at <app>/node_modules/vinext/dist/shims/, so they
hit that early return — getPackageName() yields "vinext", which matches no
framework package — and the shimsDir branch below is never reached. The
"vinext" chunk therefore never forms for any app installing vinext from npm;
it only forms from a linked checkout.

Left to graph-based splitting, the shims scatter: in a real production build
(1.0.0-beta.4, Workers target, App Router), shims/navigation-context-state.js
landed inside the browser entry chunk while shims/slot.js,
shims/error-boundary.js, and shims/navigation.js became separate
client-reference chunks, each in a static import cycle with the entry:

index-*.js -> slot-*.js           -> index-*.js
index-*.js -> error-boundary-*.js -> index-*.js
index-*.js -> navigation-*.js     -> index-*.js

Chunks are ES modules, so the chunk closing the cycle evaluates before the
entry's body has run. slot.js calls getBfcacheIdMapContext() at module
scope; that helper reads .createContext off the entry chunk's hoisted
var F = __toESM(requireReact(), 1), which is still undefined:

Uncaught TypeError: Cannot read properties of undefined (reading 'createContext')

This throws during entry evaluation, so hydration never happens — the site
server-renders and is completely inert. The build succeeds and dev is
unaffected (it doesn't chunk the same way), so nothing in the toolchain
catches it.

Fix

Check the shims prefix before the node_modules branch. shimsDir is an
absolute path into vinext's own dist/shims/, so the check is unambiguous in
both installed and linked layouts, and no react/react-dom/scheduler id can
start with it — the framework and react-dom-server groupings are
unaffected. The react-dom branch now reuses the hoisted slashedId instead
of computing its own.

No change to shimsDir construction is needed: it comes from pathslash, whose
resolve already guarantees forward slashes on Windows.

Verification

• New unit tests: an installed-layout shim id (.../node_modules/vinext/dist/shims/slot.js)
  now maps to "vinext" (fails on main), route-owned shims are still
  excluded under preserveRouteBoundaries, and framework/vendor/app ids are
  unchanged — verified against the shipped implementation across 17 id shapes,
  including pnpm layouts and ?query suffixes.
• Rebuilt a real affected app with the fix's grouping: the vinext-* chunk
  forms, the three cycles disappear, and the entry evaluates cleanly.

Notes

• Same structural failure as App Router prod build: circular chunk init crashes hydration on every route (RestorableClientStateController is not a constructor) — beta.0 & beta.1 #2620. fix(app-router): defer browser runtime controller creation #2621 made one controller lazily
  constructed but left the cyclic chunk graph in place (its own doc comment
  says the modules "may land in a circular production chunk graph"); this PR
  fixes the grouping so the cycles don't form at all.
• Since the shims branch has been unreachable for installed copies, the
  route-boundary tuning in perf(client): preserve App Router route chunk boundaries #2189/perf(client): preserve additional route-owned shims #2205 has effectively been a no-op for npm
  users; with this fix it takes effect as intended.
• App-side workaround for affected versions, until this ships: add a
  codeSplitting.groups entry for the client environment with
  test: /[\\/]node_modules[\\/]vinext[\\/]dist[\\/]shims[\\/]/ — groups
  concatenate, so vinext's own framework group is unaffected.

[pkg-pr-new]

Open in StackBlitz

npm i https://pkg.pr.new/@vinext/cloudflare@2795

npm i https://pkg.pr.new/create-vinext-app@2795

npm i https://pkg.pr.new/@vinext/types@2795

npm i https://pkg.pr.new/vinext@2795

commit: 82378a5

[Copilot]

Pull request overview

This PR fixes client production chunk grouping so vinext’s own compiled shims still get grouped into the "vinext" chunk when vinext is installed from npm (i.e., shims live under <app>/node_modules/vinext/dist/shims/). This prevents Rolldown’s graph-based splitting from scattering shims into separate chunks that can form static import cycles with the browser entry chunk and break hydration at runtime.

Changes:

• Make the "vinext" shims grouping check run before the node_modules early-return logic in createClientManualChunks.
• Reuse the hoisted slashedId for the react-dom subpath classification.
• Add unit tests covering the “installed layout” (.../node_modules/vinext/dist/shims/...) and ensuring existing route-boundary exclusions and framework grouping remain intact.

Reviewed changes

Copilot reviewed 2 out of 2 changed files in this pull request and generated no comments.

File	Description
packages/vinext/src/build/client-build-config.ts	Moves shims detection ahead of the node_modules branch so installed-copy shims reliably map to the "vinext" chunk; reuses slashedId in the react-dom path logic.
tests/build-optimization.test.ts	Adds focused regression tests for installed-layout shim IDs, plus assertions that preserve-route-boundary and framework/vendor behavior is unchanged.

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[github-actions]

Performance benchmarks

Compared 82378a5 against base ced0881 using alternating same-runner rounds. Next.js was unchanged and skipped.

0 improved · 0 regressed · 6 within ±1.5%

Scenario	Framework	Baseline	Current	Change
Client bundle size (gzip)	vinext	134.6 KB	134.6 KB	⚫ +0.0%
Client entry size (gzip)	vinext	122.1 KB	122.1 KB	⚫ +0.0%
Dev server cold start	vinext	3.01 s	2.99 s	⚫ -0.9%
Production build time	vinext	3.33 s	3.30 s	⚫ -0.8%
RSC entry closure size (gzip)	vinext	112.4 KB	112.4 KB	⚫ -0.0%
Server bundle size (gzip)	vinext	189.9 KB	189.9 KB	⚫ -0.0%

View detailed results and traces

_{🟢 improvement · 🔴 regression · ⚫ change below 1.5% · paired base/head}