feat: lib chunks

[pi0]

With introduction of bundling by default in next release, libs (node_module dependnecies) are bundled by default which is more efficient thant tracing as libs are tree-shaken but making debugging harder with chunk groups containing both user code and libraries.

One solution is to simply use better chunk names but it still has issue of mixed code. This PR uses chunk groups to explicitly seperate each bundled dependency by name.

This change will also be useful in the future for low-effort bundle analysis.

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Project	Deployment	Preview	Comments	Updated (UTC)
nitro.build	Ready	Preview	Comment	Dec 10, 2025 4:49pm

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📥 Commits

Reviewing files that changed from the base of the PR and between c15f7bd and 1fdb9d1.

📒 Files selected for processing (2)

• src/build/rolldown/config.ts (4 hunks)
• src/build/rollup/config.ts (3 hunks)

📝 Walkthrough

Walkthrough

Refactors chunk naming: adds NODE_MODULES_RE and libChunkName, changes getChunkName to accept a chunk object and expands routing for libs, runtime, WASM, SSR, build/runtime/routes/tasks, and updates build configs to group node_modules via advancedChunks/manualChunks.

Changes

Cohort / File(s)	Change Summary
Core chunk naming and routing src/build/chunks.ts	Added exported NODE_MODULES_RE and libChunkName. Reworked getChunkName signature to getChunkName(chunk: { name: string; moduleIds: string[] }, nitro) and expanded routing (handles _libs/, rolldown-runtime, WASM, SSR, _build, runtime/presets, routes, tasks, virtual/raw chunks). Removed parseNodeModulePath usage and simplified default chunk path to _chunks/[name].mjs.
Rolldown build config src/build/rolldown/config.ts	Switched chunkFileNames usage to getChunkName(chunk, nitro). Added advancedChunks grouping for node_modules using NODE_MODULES_RE and libChunkName. Removed sanitizeFilePath/sanitize option. Adjusted types and conditional removal of advancedChunks for iife output.
Rollup build config src/build/rollup/config.ts	Updated imports to use libChunkName and NODE_MODULES_RE. Changed chunk filename generation to getChunkName(chunk, nitro). Added manualChunks hook to group node_modules via libChunkName. Removed sanitizeFilePath. Added explicit typing and conditional removal of manualChunks for iife.
Vite/Rollup integration src/build/vite/rollup.ts	Replaced getChunkName(nitro, chunk.moduleIds) with getChunkName(chunk, nitro). When using Rolldown, adds advancedChunks with NODE_MODULES_RE/libChunkName; otherwise sets manualChunks for node_modules. Removed sanitizeFilePath import and adjusted chunking strategy based on build mode.

Estimated code review effort

🎯 3 (Moderate) | ⏱️ ~25 minutes

• Pay extra attention to getChunkName decision branches handling virtual vs raw moduleIds and the newly added chunk-type checks (WASM, SSR, runtime, routes, tasks).
• Verify libChunkName produces deterministic names for mixed/monorepo package paths and that NODE_MODULES_RE pattern covers targeted modules.
• Confirm advancedChunks vs manualChunks behavior is correctly toggled/removed for iife outputs and that removing sanitizeFilePath doesn't introduce unsafe filenames.

Pre-merge checks and finishing touches

❌ 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%.	You can run @coderabbitai generate docstrings to improve docstring coverage.

✅ Passed checks (2 passed)

Check name	Status	Explanation
Title check	✅ Passed	The title 'feat: lib chunks' follows conventional commits format with 'feat:' prefix and clearly describes the main change: introducing library chunk separation.
Description check	✅ Passed	The description explains the problem (mixed code in chunks when bundling libs) and the solution (explicit separation by name), directly related to the changeset.

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[coderabbitai]

Actionable comments posted: 0

🧹 Nitpick comments (1)

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

70-70: Consider removing the commented-out code.

The commented sanitizeFileName: sanitizeFilePath line should either be removed entirely or include a brief comment explaining why it's retained (e.g., for future reference or pending upstream support).

-      // sanitizeFileName: sanitizeFilePath,

📜 Review details

Configuration used: CodeRabbit UI

Review profile: CHILL

Plan: Pro

📥 Commits

Reviewing files that changed from the base of the PR and between 4d2e6b8 and c929557.

📒 Files selected for processing (4)

• src/build/chunks.ts (2 hunks)
• src/build/rolldown/config.ts (2 hunks)
• src/build/rollup/config.ts (2 hunks)
• src/build/vite/rollup.ts (2 hunks)

🧰 Additional context used

🧬 Code graph analysis (4)

src/build/rolldown/config.ts (1)

src/build/chunks.ts (3)

• getChunkName (15-83)
• NODE_MODULES_RE (6-6)
• libChunkName (8-13)

src/build/chunks.ts (1)

src/types/nitro.ts (1)

• Nitro (16-37)

src/build/rollup/config.ts (1)

src/build/chunks.ts (3)

• getChunkName (15-83)
• NODE_MODULES_RE (6-6)
• libChunkName (8-13)

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

src/build/chunks.ts (3)

• getChunkName (15-83)
• NODE_MODULES_RE (6-6)
• libChunkName (8-13)

⏰ Context from checks skipped due to timeout of 90000ms. You can increase the timeout in your CodeRabbit configuration to a maximum of 15 minutes (900000ms). (2)

• GitHub Check: tests-rollup (ubuntu-latest)
• GitHub Check: tests-rollup (windows-latest)

🔇 Additional comments (7)

src/build/rolldown/config.ts (1)

56-59: LGTM! Clean implementation of lib chunking for Rolldown.

The advancedChunks configuration correctly uses NODE_MODULES_RE to identify node_modules and libChunkName to generate consistent chunk names. This aligns well with the PR objective of separating bundled dependencies into distinct chunks.

src/build/rollup/config.ts (1)

74-85: LGTM! Consistent lib chunking implementation for Rollup.

The manualChunks hook correctly mirrors the Rolldown implementation using Rollup's native API. The pattern of testing with NODE_MODULES_RE and returning libChunkName(id) ensures consistent chunk naming across both bundlers.

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

45-63: LGTM! Correct conditional chunking for Vite's dual bundler support.

The implementation properly handles both Rolldown (using advancedChunks) and standard Rollup (using manualChunks) paths. The logic is consistent with the standalone config files.

src/build/chunks.ts (4)

6-13: LGTM! Well-designed regex patterns for node_modules handling.

The NODE_MODULES_RE correctly excludes hidden directories (like .bin, .cache) by requiring a non-dot character after the separator. The libChunkName regex properly handles both scoped (@scope/package) and unscoped packages with a sensible fallback to "common".

---

15-30: Clear chunk categorization with early returns.

The known-group handling for _libs/ prefix and rolldown-runtime provides clean early exits before the more complex classification logic. The empty moduleIds guard is a sensible defensive check.

---

85-96: Route path sanitization looks reasonable.

The routeToFsPath function handles dynamic route segments (:param, *wildcard) by converting them to $ prefixes, and sanitizes other special characters. The fallback to "index" for root routes is appropriate.

---

64-80: Verify bundler ordering guarantees for handler matching.

The logic using ids.at(-1) assumes the last non-virtual module ID in a chunk corresponds to the handler entry point. This assumption is unvalidated since the handler matching logic was newly introduced in the recent chunk naming refactor. Confirm whether Rollup/Rolldown guarantee module ordering such that entry-point handlers consistently appear as the last module in their chunks, or add defensive checks (e.g., match against any module ID in the chunk, not just the last).

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commit: 1fdb9d1