fix(vite): invalidate shared modules in SSR environment on HMR

[Nazaire]

Modules present in both client and server environments were skipped during server-side invalidation due to an overly strict guard. This caused SSR to render stale HTML after HMR updates, leading to React hydration mismatches.

🔗 Linked issue

Fixes #4043
Related to #4020

❓ Type of change

• 🐞 Bug fix (a non-breaking change that fixes an issue)

📚 Description

In src/build/vite/plugin.ts, the hotUpdate hook skipped server-side
invalidation for any module that also exists in a client environment:

if (mod.id && !clientEnvs.some((env) => env.moduleGraph.getModuleById(mod.id!))) {
  hasServerOnlyModule = true;
  env.moduleGraph.invalidateModule(mod, invalidated, timestamp, false);
}

The !clientEnvs.some(...) guard means: if a module is present in a client
environment, don't invalidate it in the server environment. The intent was
presumably to defer to Vite's normal client HMR — but the server-side copy of
that module still needs invalidation for SSR to re-render correctly.

The fix removes the exclusion guard so that all modules with an id are
invalidated in the server module graph on HMR, regardless of whether they also
appear in a client environment.

📝 Checklist

• I have linked an issue or discussion.
• I have updated the documentation accordingly.

[vercel]

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[coderabbitai]

📝 Walkthrough

Walkthrough

This change modifies Nitro's Vite plugin hotUpdate hook to invalidate server-side module caches for all modules with valid IDs, rather than only server-only modules. Previously, shared modules (e.g., React components used in SSR) were not invalidated during development, causing hydration mismatches.

Changes

Cohort / File(s)	Summary
HMR Module Invalidation src/build/vite/plugin.ts	Updated hotUpdate detection logic to invalidate all modules with valid IDs and trigger full reload accordingly, fixing incomplete invalidation of shared server-side modules during development.

Estimated code review effort

🎯 2 (Simple) | ⏱️ ~10 minutes

🚥 Pre-merge checks | ✅ 4 | ❌ 1

❌ Failed checks (1 warning)

Check name	Status	Explanation	Resolution
Docstring Coverage	⚠️ Warning	Docstring coverage is 0.00% which is insufficient. The required threshold is 80.00%.	Write docstrings for the functions missing them to satisfy the coverage threshold.

✅ Passed checks (4 passed)

Check name	Status	Explanation
Title check	✅ Passed	The title follows conventional commits format with 'fix' prefix and clearly describes the bug fix for invalidating shared modules in SSR on HMR.
Description check	✅ Passed	The description is directly related to the changeset, clearly explaining the bug, the problematic code, and the fix applied to the module invalidation logic.
Linked Issues check	✅ Passed	The PR successfully addresses issue #4043 by ensuring server-side module invalidation for shared modules during HMR, preventing stale SSR renders and hydration mismatches.
Out of Scope Changes check	✅ Passed	All changes in src/build/vite/plugin.ts are directly scoped to fixing the server-side module invalidation issue; no extraneous changes are present.

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✨ Finishing Touches

• 📝 Generate docstrings

🧪 Generate unit tests (beta)

• Create PR with unit tests
• Post copyable unit tests in a comment

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[coderabbitai]

🧹 Nitpick comments (1)

src/build/vite/plugin.ts (1)

251-253: clientEnvs is now dead code — remove it.

After removing the clientEnvs.some(...) exclusion guard, the clientEnvs variable is computed but never read. It should be deleted.

♻️ Proposed fix

-      const clientEnvs = Object.values(server.environments).filter(
-        (env) => env.config.consumer === "client"
-      );
       let hasServerModule = false;

🤖 Prompt for AI Agents

Verify each finding against the current code and only fix it if needed.

In `@src/build/vite/plugin.ts` around lines 251 - 253, Remove the now-unused
clientEnvs variable declaration in src/build/vite/plugin.ts: delete the const
clientEnvs = Object.values(server.environments).filter((env) =>
env.config.consumer === "client"); line (it is dead after the
clientEnvs.some(...) guard was removed) so no unused variable remains in the
surrounding function/block.

🤖 Prompt for all review comments with AI agents

Verify each finding against the current code and only fix it if needed.

Nitpick comments:
In `@src/build/vite/plugin.ts`:
- Around line 251-253: Remove the now-unused clientEnvs variable declaration in
src/build/vite/plugin.ts: delete the const clientEnvs =
Object.values(server.environments).filter((env) => env.config.consumer ===
"client"); line (it is dead after the clientEnvs.some(...) guard was removed) so
no unused variable remains in the surrounding function/block.