fix(vite): clear module runner cache before dev worker reload

[brenelz]

🔗 Linked issue

Resolves item (3) of #4472. Same root cause as #4020 (closed, but the fix never landed). Related to #4043.

❓ Type of change

• 📖 Documentation (updates to the documentation, readme, or JSdoc annotations)
• 🐞 Bug fix (a non-breaking change that fixes an issue)
• 👌 Enhancement (improving an existing functionality like performance)
• ✨ New feature (a non-breaking change that adds functionality)
• 🧹 Chore (updates to the build process or auxiliary tools and libraries)
• ⚠️ Breaking change (fix or feature that would cause existing functionality to change)

📚 Description

ViteEnvRunner.reload() in the dev worker re-imports the environment entry without clearing the ModuleRunner's evaluatedModules cache.

The runner's fetchModule protocol answers {cache: true} for any module whose transform is already populated on the Vite side at fetch time (packages/vite's fetchModule: if (options.cached && cached) return { cache: true }). During a dev-worker reload, plugin-side crawls can repopulate transforms for large parts of the graph before the runner re-fetches them (observed with vite-plugin-solid's ?assets transform), so the re-import walks the entry but keeps stale evaluations for the very modules that changed — the server renders old code until the dev server is restarted, causing SSR/client hydration mismatches.

Vite's own full-reload handler in the module runner clears evaluatedModules before re-importing (hmrHandler.ts); this PR does the same in the worker's reload().

Verified against a Vite 8 + vite-plugin-solid SSR app: with this change (plus a full-reload actually being sent for shared modules — see #4472 items 1–2), edits to SSR-rendered modules are reflected on the next request without restarting the dev server, and hydration is clean. NITRO_DEBUG=1 traces confirm all app modules re-execute after reload instead of being served from the stale cache.

Includes a regression test in the vite:hmr suite: the fixture gains a dep-crawler plugin that re-transforms dep.ts as a side effect of transforming api/crawled.ts (the way asset-collecting plugins crawl imports), plus a plugin that hard-invalidates the server module graph on dep.ts edits (as framework staleness workarounds do in the wild). Without evaluatedModules.clear() the crawled transform makes fetchModule answer {cache: true} for dep.ts and the test times out on the stale response; with the fix it passes.

📝 Checklist

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

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[coderabbitai]

📝 Walkthrough

Walkthrough

Vite reloads now clear evaluated module state before re-importing the entry module. HMR fixtures and plugins reproduce dependency crawling and graph invalidation, while a regression test verifies updated API output and a full-reload message.

Changes

Vite reload cache handling

Layer / File(s)	Summary
Reset evaluated modules during reload src/runtime/internal/vite/dev-worker.mjs	ViteEnvRunner.reload() clears evaluated modules before re-importing the entry module.
Exercise dependency graph invalidation test/vite/hmr-fixture/dep.ts, test/vite/hmr-fixture/api/crawled.ts, test/vite/hmr-fixture/vite.config.ts	The HMR fixture adds a dependency value, a consuming API module, and plugins that crawl and invalidate the server module graph.
Validate refreshed dependency output test/vite/hmr.test.ts	The regression test edits dep.ts, verifies the crawled API returns the new value, and checks for a full-reload message.

Estimated code review effort: 2 (Simple) | ~10 minutes

Possibly related issues

• Vite dev: SSR serves stale modules after edits — no reload for shared modules, missing file associations, and dev-worker reload() reuses cached evaluations #4472 — Directly addresses the cached-evaluation problem in ViteEnvRunner.reload().

Possibly related PRs

• nitrojs/nitro#3836 — Also changes environment-runner reload behavior in the internal Vite runner.

🚥 Pre-merge checks | ✅ 5

✅ Passed checks (5 passed)

Check name	Status	Explanation
Docstring Coverage	✅ Passed	No functions found in the changed files to evaluate docstring coverage. Skipping docstring coverage check.
Linked Issues check	✅ Passed	Check skipped because no linked issues were found for this pull request.
Out of Scope Changes check	✅ Passed	Check skipped because no linked issues were found for this pull request.
Title check	✅ Passed	The title follows conventional commits and accurately describes the cache-clearing reload fix.
Description check	✅ Passed	The description directly matches the PR's Vite dev worker reload cache fix and regression test.

✨ Finishing Touches

🧪 Generate unit tests (beta)

• Create PR with unit tests

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[pi0]

Would be nice to add a regression test to vite-hmr fixture!

[pkg-pr-new]

Open in StackBlitz

npm i https://pkg.pr.new/nitro@4473

commit: b6bcf72